Packages

final class LazyList[+A] extends AbstractSeq[A] with LinearSeq[A] with LinearSeqOps[A, LazyList, LazyList[A]] with IterableFactoryDefaults[A, LazyList] with Serializable

This class implements an immutable linked list. We call it "lazy" because it computes its elements only when they are needed.

Elements are memoized; that is, the value of each element is computed at most once.

Elements are computed in-order and are never skipped. In other words, accessing the tail causes the head to be computed first.

How lazy is a LazyList? When you have a value of type LazyList, you don't know yet whether the list is empty or not. If you learn that it is non-empty, then you also know that the head has been computed. But the tail is itself a LazyList, whose emptiness-or-not might remain undetermined.

A LazyList may be infinite. For example, LazyList.from(0) contains all of the natural numbers 0, 1, 2, and so on. For infinite sequences, some methods (such as count, sum, max or min) will not terminate.

Here is an example:

import scala.math.BigInt
object Main extends App {
  val fibs: LazyList[BigInt] =
    BigInt(0) #:: BigInt(1) #:: fibs.zip(fibs.tail).map{ n => n._1 + n._2 }
  fibs.take(5).foreach(println)
}

// prints
//
// 0
// 1
// 1
// 2
// 3

To illustrate, let's add some output to the definition fibs, so we see what's going on.

import scala.math.BigInt
object Main extends App {
  val fibs: LazyList[BigInt] =
    BigInt(0) #:: BigInt(1) #::
      fibs.zip(fibs.tail).map{ n =>
        println(s"Adding ${n._1} and ${n._2}")
        n._1 + n._2
      }
  fibs.take(5).foreach(println)
  fibs.take(6).foreach(println)
}

// prints
//
// 0
// 1
// Adding 0 and 1
// 1
// Adding 1 and 1
// 2
// Adding 1 and 2
// 3

// And then prints
//
// 0
// 1
// 1
// 2
// 3
// Adding 2 and 3
// 5

Note that the definition of fibs uses val not def. The memoization of the LazyList requires us to have somewhere to store the information and a val allows us to do that.

Further remarks about the semantics of LazyList:

  • Though the LazyList changes as it is accessed, this does not contradict its immutability. Once the values are memoized they do not change. Values that have yet to be memoized still "exist", they simply haven't been computed yet.
  • One must be cautious of memoization; it can eat up memory if you're not careful. That's because memoization of the LazyList creates a structure much like scala.collection.immutable.List. As long as something is holding on to the head, the head holds on to the tail, and so on recursively. If, on the other hand, there is nothing holding on to the head (e.g. if we used def to define the LazyList) then once it is no longer being used directly, it disappears.
  • Note that some operations, including drop, dropWhile, flatMap or collect may process a large number of intermediate elements before returning.

Here's another example. Let's start with the natural numbers and iterate over them.

// We'll start with a silly iteration
def loop(s: String, i: Int, iter: Iterator[Int]): Unit = {
  // Stop after 200,000
  if (i < 200001) {
    if (i % 50000 == 0) println(s + i)
    loop(s, iter.next(), iter)
  }
}

// Our first LazyList definition will be a val definition
val lazylist1: LazyList[Int] = {
  def loop(v: Int): LazyList[Int] = v #:: loop(v + 1)
  loop(0)
}

// Because lazylist1 is a val, everything that the iterator produces is held
// by virtue of the fact that the head of the LazyList is held in lazylist1
val it1 = lazylist1.iterator
loop("Iterator1: ", it1.next(), it1)

// We can redefine this LazyList such that all we have is the Iterator left
// and allow the LazyList to be garbage collected as required.  Using a def
// to provide the LazyList ensures that no val is holding onto the head as
// is the case with lazylist1
def lazylist2: LazyList[Int] = {
  def loop(v: Int): LazyList[Int] = v #:: loop(v + 1)
  loop(0)
}
val it2 = lazylist2.iterator
loop("Iterator2: ", it2.next(), it2)

// And, of course, we don't actually need a LazyList at all for such a simple
// problem.  There's no reason to use a LazyList if you don't actually need
// one.
val it3 = new Iterator[Int] {
  var i = -1
  def hasNext = true
  def next(): Int = { i += 1; i }
}
loop("Iterator3: ", it3.next(), it3)
  • In the fibs example earlier, the fact that tail works at all is of interest. fibs has an initial (0, 1, LazyList(...)), so tail is deterministic. If we defined fibs such that only 0 were concretely known, then the act of determining tail would require the evaluation of tail, so the computation would be unable to progress, as in this code:
// The first time we try to access the tail we're going to need more
// information which will require us to recurse, which will require us to
// recurse, which...
lazy val sov: LazyList[Vector[Int]] = Vector(0) #:: sov.zip(sov.tail).map { n => n._1 ++ n._2 }

The definition of fibs above creates a larger number of objects than necessary depending on how you might want to implement it. The following implementation provides a more "cost effective" implementation due to the fact that it has a more direct route to the numbers themselves:

lazy val fib: LazyList[Int] = {
  def loop(h: Int, n: Int): LazyList[Int] = h #:: loop(n, h + n)
  loop(1, 1)
}

The head, the tail and whether the list is empty or not can be initially unknown. Once any of those are evaluated, they are all known, though if the tail is built with #:: or #:::, it's content still isn't evaluated. Instead, evaluating the tails content is deferred until the tails empty status, head or tail is evaluated.

Delaying the evaluation of whether a LazyList is empty or not until it's needed allows LazyList to not eagerly evaluate any elements on a call to filter.

Only when it's further evaluated (which may be never!) any of the elements gets forced.

for example:

def tailWithSideEffect: LazyList[Nothing] = {
  println("getting empty LazyList")
  LazyList.empty
}

val emptyTail = tailWithSideEffect // prints "getting empty LazyList"

val suspended = 1 #:: tailWithSideEffect // doesn't print anything
val tail = suspended.tail // although the tail is evaluated, *still* nothing is yet printed
val filtered = tail.filter(_ => false) // still nothing is printed
filtered.isEmpty // prints "getting empty LazyList"
A

the type of the elements contained in this lazy list.

Annotations
@SerialVersionUID()
Source
LazyList.scala
See also

"Scala's Collection Library overview" section on LazyLists for more information.

Type Hierarchy
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Inherited
  1. LazyList
  2. Serializable
  3. LinearSeq
  4. LinearSeqOps
  5. LinearSeq
  6. LinearSeqOps
  7. AbstractSeq
  8. Seq
  9. SeqOps
  10. Iterable
  11. AbstractSeq
  12. Seq
  13. Equals
  14. SeqOps
  15. PartialFunction
  16. Function1
  17. AbstractIterable
  18. Iterable
  19. IterableFactoryDefaults
  20. IterableOps
  21. IterableOnceOps
  22. IterableOnce
  23. AnyRef
  24. Any
Implicitly
  1. by UnliftOps
  2. by iterableOnceExtensionMethods
  3. by toDeferrer
  4. by any2stringadd
  5. by StringFormat
  6. by Ensuring
  7. by ArrowAssoc
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Visibility
  1. Public
  2. Protected

Value Members

  1. final def !=(arg0: Any): Boolean

    Test two objects for inequality.

    Test two objects for inequality.

    returns

    true if !(this == that), false otherwise.

    Definition Classes
    AnyRef → Any
  2. final def ##: Int

    Equivalent to x.hashCode except for boxed numeric types and null.

    Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.

    returns

    a hash value consistent with ==

    Definition Classes
    AnyRef → Any
  3. def #::[B >: A](elem: => B): LazyList[B]

    Construct a LazyList consisting of a given first element followed by elements from another LazyList.

    Construct a LazyList consisting of a given first element followed by elements from another LazyList.

    Implicit
    This member is added by an implicit conversion from LazyList[A] toDeferrer[A] performed by method toDeferrer in scala.collection.immutable.LazyList.
    Definition Classes
    Deferrer
  4. def #:::[B >: A](prefix: LazyList[B]): LazyList[B]

    Construct a LazyList consisting of the concatenation of the given LazyList and another LazyList.

    Construct a LazyList consisting of the concatenation of the given LazyList and another LazyList.

    Implicit
    This member is added by an implicit conversion from LazyList[A] toDeferrer[A] performed by method toDeferrer in scala.collection.immutable.LazyList.
    Definition Classes
    Deferrer
  5. def +(other: String): String
    Implicit
    This member is added by an implicit conversion from LazyList[A] toany2stringadd[LazyList[A]] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  6. final def ++[B >: A](suffix: IterableOnce[B]): LazyList[B]

    Alias for concat

    Alias for concat

    Definition Classes
    IterableOps
    Annotations
    @inline()
  7. final def ++:[B >: A](prefix: IterableOnce[B]): LazyList[B]

    Alias for prependedAll

    Alias for prependedAll

    Definition Classes
    SeqOpsIterableOps
    Annotations
    @inline()
  8. final def +:[B >: A](elem: B): LazyList[B]

    Alias for prepended.

    Alias for prepended.

    Note that :-ending operators are right associative (see example). A mnemonic for +: vs. :+ is: the COLon goes on the COLlection side.

    Definition Classes
    SeqOps
    Annotations
    @inline()
  9. def ->[B](y: B): (LazyList[A], B)
    Implicit
    This member is added by an implicit conversion from LazyList[A] toArrowAssoc[LazyList[A]] performed by method ArrowAssoc in scala.Predef.This conversion will take place only if A is a subclass of Option[Nothing] (A <: Option[Nothing]).
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  10. final def :+[B >: A](elem: B): LazyList[B]

    Alias for appended

    Alias for appended

    Note that :-ending operators are right associative (see example). A mnemonic for +: vs. :+ is: the COLon goes on the COLlection side.

    Definition Classes
    SeqOps
    Annotations
    @inline()
  11. final def :++[B >: A](suffix: IterableOnce[B]): LazyList[B]

    Alias for appendedAll

    Alias for appendedAll

    Definition Classes
    SeqOps
    Annotations
    @inline()
  12. final def ==(arg0: Any): Boolean

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any
  13. def addString(sb: mutable.StringBuilder, start: String, sep: String, end: String): mutable.StringBuilder

    Appends all elements of this lazy list to a string builder using start, end, and separator strings.

    Appends all elements of this lazy list to a string builder using start, end, and separator strings. The written text begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this lazy list are separated by the string sep.

    An undefined state is represented with "<not computed>" and cycles are represented with "<cycle>".

    This method evaluates all elements of the collection.

    sb

    the string builder to which elements are appended.

    start

    the starting string.

    sep

    the separator string.

    end

    the ending string.

    returns

    the string builder b to which elements were appended.

    Definition Classes
    LazyListIterableOnceOps
  14. final def addString(b: mutable.StringBuilder): mutable.StringBuilder

    Appends all elements of this collection to a string builder.

    Appends all elements of this collection to a string builder. The written text consists of the string representations (w.r.t. the method toString) of all elements of this collection without any separator string.

    Example:

    scala> val a = List(1,2,3,4)
    a: List[Int] = List(1, 2, 3, 4)
    
    scala> val b = new StringBuilder()
    b: StringBuilder =
    
    scala> val h = a.addString(b)
    h: StringBuilder = 1234
    b

    the string builder to which elements are appended.

    returns

    the string builder b to which elements were appended.

    Definition Classes
    IterableOnceOps
    Annotations
    @inline()
  15. final def addString(b: mutable.StringBuilder, sep: String): mutable.StringBuilder

    Appends all elements of this collection to a string builder using a separator string.

    Appends all elements of this collection to a string builder using a separator string. The written text consists of the string representations (w.r.t. the method toString) of all elements of this collection, separated by the string sep.

    Example:

    scala> val a = List(1,2,3,4)
    a: List[Int] = List(1, 2, 3, 4)
    
    scala> val b = new StringBuilder()
    b: StringBuilder =
    
    scala> a.addString(b, ", ")
    res0: StringBuilder = 1, 2, 3, 4
    b

    the string builder to which elements are appended.

    sep

    the separator string.

    returns

    the string builder b to which elements were appended.

    Definition Classes
    IterableOnceOps
    Annotations
    @inline()
  16. def andThen[C](k: PartialFunction[A, C]): PartialFunction[Int, C]

    Composes this partial function with another partial function that gets applied to results of this partial function.

    Composes this partial function with another partial function that gets applied to results of this partial function.

    Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.

    C

    the result type of the transformation function.

    k

    the transformation function

    returns

    a partial function with the domain of this partial function narrowed by other partial function, which maps arguments x to k(this(x)).

    Definition Classes
    PartialFunction
  17. def andThen[C](k: (A) => C): PartialFunction[Int, C]

    Composes this partial function with a transformation function that gets applied to results of this partial function.

    Composes this partial function with a transformation function that gets applied to results of this partial function.

    If the runtime type of the function is a PartialFunction then the other andThen method is used (note its cautions).

    C

    the result type of the transformation function.

    k

    the transformation function

    returns

    a partial function with the domain of this partial function, possibly narrowed by the specified function, which maps arguments x to k(this(x)).

    Definition Classes
    PartialFunctionFunction1
  18. def appended[B >: A](elem: B): LazyList[B]

    A copy of this lazy list with an element appended.

    A copy of this lazy list with an element appended.

    Note: will not terminate for infinite-sized collections.

    Example:

    scala> val a = List(1)
    a: List[Int] = List(1)
    
    scala> val b = a :+ 2
    b: List[Int] = List(1, 2)
    
    scala> println(a)
    List(1)

    This method preserves laziness; elements are only evaluated individually as needed.

    Note: Repeated chaining of calls to append methods (appended, appendedAll, lazyAppendedAll) without forcing any of the intermediate resulting lazy lists may overflow the stack when the final result is forced.

    B

    the element type of the returned lazy list.

    elem

    the appended element

    returns

    a new lazy list consisting of all elements of this lazy list followed by value.

    Definition Classes
    LazyListSeqOps
  19. def appendedAll[B >: A](suffix: IterableOnce[B]): LazyList[B]

    Returns a new lazy list containing the elements from the left hand operand followed by the elements from the right hand operand.

    Returns a new lazy list containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the lazy list is the most specific superclass encompassing the element types of the two operands.

    This method preserves laziness; elements are only evaluated individually as needed.

    Note: Repeated chaining of calls to append methods (appended, appendedAll, lazyAppendedAll) without forcing any of the intermediate resulting lazy lists may overflow the stack when the final result is forced.

    B

    the element type of the returned collection.

    suffix

    the iterable to append.

    returns

    a new collection of type CC[B] which contains all elements of this lazy list followed by all elements of suffix.

    Definition Classes
    LazyListSeqOps
  20. def apply(n: Int): A

    Get the element at the specified index.

    Get the element at the specified index. This operation is provided for convenience in Seq. It should not be assumed to be efficient unless you have an IndexedSeq.

    Definition Classes
    LinearSeqOpsSeqOps
    Annotations
    @throws(cause = scala.this.throws.<init>$default$1[IndexOutOfBoundsException])
  21. def applyOrElse[A1 <: Int, B1 >: A](x: A1, default: (A1) => B1): B1

    Applies this partial function to the given argument when it is contained in the function domain.

    Applies this partial function to the given argument when it is contained in the function domain. Applies fallback function where this partial function is not defined.

    Note that expression pf.applyOrElse(x, default) is equivalent to

    if(pf isDefinedAt x) pf(x) else default(x)

    except that applyOrElse method can be implemented more efficiently. For all partial function literals the compiler generates an applyOrElse implementation which avoids double evaluation of pattern matchers and guards. This makes applyOrElse the basis for the efficient implementation for many operations and scenarios, such as:

    • combining partial functions into orElse/andThen chains does not lead to excessive apply/isDefinedAt evaluation
    • lift and unlift do not evaluate source functions twice on each invocation
    • runWith allows efficient imperative-style combining of partial functions with conditionally applied actions

    For non-literal partial function classes with nontrivial isDefinedAt method it is recommended to override applyOrElse with custom implementation that avoids double isDefinedAt evaluation. This may result in better performance and more predictable behavior w.r.t. side effects.

    x

    the function argument

    default

    the fallback function

    returns

    the result of this function or fallback function application.

    Definition Classes
    PartialFunction
  22. final def asInstanceOf[T0]: T0

    Cast the receiver object to be of type T0.

    Cast the receiver object to be of type T0.

    Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

    returns

    the receiver object.

    Definition Classes
    Any
    Exceptions thrown

    ClassCastException if the receiver object is not an instance of the erasure of type T0.

  23. def canEqual(that: Any): Boolean

    Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.

    Method called from equality methods, so that user-defined subclasses can refuse to be equal to other collections of the same kind.

    that

    The object with which this sequence should be compared

    returns

    true, if this sequence can possibly equal that, false otherwise. The test takes into consideration only the run-time types of objects but ignores their elements.

    Definition Classes
    SeqEquals
  24. def className: String

    Defines the prefix of this object's toString representation.

    Defines the prefix of this object's toString representation.

    It is recommended to return the name of the concrete collection type, but not implementation subclasses. For example, for ListMap this method should return "ListMap", not "Map" (the supertype) or "Node" (an implementation subclass).

    The default implementation returns "Iterable". It is overridden for the basic collection kinds "Seq", "IndexedSeq", "LinearSeq", "Buffer", "Set", "Map", "SortedSet", "SortedMap" and "View".

    returns

    a string representation which starts the result of toString applied to this lazy list. By default the string prefix is the simple name of the collection class lazy list.

    Attributes
    protected[this]
    Definition Classes
    LazyListIterable
  25. def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the clone method is platform dependent.

    returns

    a copy of the receiver object.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  26. final def coll: LazyList.this.type

    returns

    This collection as a C.

    Attributes
    protected
    Definition Classes
    IterableIterableOps
  27. def collect[B](pf: PartialFunction[A, B]): LazyList[B]

    Builds a new lazy list by applying a partial function to all elements of this lazy list on which the function is defined.

    Builds a new lazy list by applying a partial function to all elements of this lazy list on which the function is defined.

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the element type of the returned lazy list.

    pf

    the partial function which filters and maps the lazy list.

    returns

    a new lazy list resulting from applying the given partial function pf to each element on which it is defined and collecting the results. The order of the elements is preserved.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  28. def collectFirst[B](pf: PartialFunction[A, B]): Option[B]

    Finds the first element of the lazy list for which the given partial function is defined, and applies the partial function to it.

    Finds the first element of the lazy list for which the given partial function is defined, and applies the partial function to it.

    Note: may not terminate for infinite-sized collections.

    This method does not evaluate any elements further than the first element for which the partial function is defined.

    pf

    the partial function

    returns

    an option value containing pf applied to the first value for which it is defined, or None if none exists.

    Definition Classes
    LazyListIterableOnceOps
    Annotations
    @tailrec()
  29. def combinations(n: Int): Iterator[LazyList[A]]

    Iterates over combinations.

    Iterates over combinations. A _combination_ of length n is a subsequence of the original sequence, with the elements taken in order. Thus, "xy" and "yy" are both length-2 combinations of "xyy", but "yx" is not. If there is more than one way to generate the same subsequence, only one will be returned.

    For example, "xyyy" has three different ways to generate "xy" depending on whether the first, second, or third "y" is selected. However, since all are identical, only one will be chosen. Which of the three will be taken is an implementation detail that is not defined.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    returns

    An Iterator which traverses the possible n-element combinations of this sequence.

    Definition Classes
    SeqOps
    Example:
    1. "abbbc".combinations(2) = Iterator(ab, ac, bb, bc)

  30. def compose[R](k: PartialFunction[R, Int]): PartialFunction[R, A]

    Composes another partial function k with this partial function so that this partial function gets applied to results of k.

    Composes another partial function k with this partial function so that this partial function gets applied to results of k.

    Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.

    R

    the parameter type of the transformation function.

    k

    the transformation function

    returns

    a partial function with the domain of other partial function narrowed by this partial function, which maps arguments x to this(k(x)).

    Definition Classes
    PartialFunction
  31. def compose[A](g: (A) => Int): (A) => A

    Composes two instances of Function1 in a new Function1, with this function applied last.

    Composes two instances of Function1 in a new Function1, with this function applied last.

    A

    the type to which function g can be applied

    g

    a function A => T1

    returns

    a new function f such that f(x) == apply(g(x))

    Definition Classes
    Function1
    Annotations
    @unspecialized()
  32. final def concat[B >: A](suffix: IterableOnce[B]): LazyList[B]

    Returns a new sequence containing the elements from the left hand operand followed by the elements from the right hand operand.

    Returns a new sequence containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the sequence is the most specific superclass encompassing the element types of the two operands.

    B

    the element type of the returned collection.

    suffix

    the traversable to append.

    returns

    a new sequence which contains all elements of this sequence followed by all elements of suffix.

    Definition Classes
    SeqOpsIterableOps
    Annotations
    @inline()
  33. def contains[A1 >: A](elem: A1): Boolean

    Tests whether this sequence contains a given value as an element.

    Tests whether this sequence contains a given value as an element.

    Note: may not terminate for infinite-sized collections.

    elem

    the element to test.

    returns

    true if this sequence has an element that is equal (as determined by ==) to elem, false otherwise.

    Definition Classes
    LinearSeqOpsSeqOps
  34. def containsSlice[B](that: collection.Seq[B]): Boolean

    Tests whether this sequence contains a given sequence as a slice.

    Tests whether this sequence contains a given sequence as a slice.

    Note: may not terminate for infinite-sized collections.

    that

    the sequence to test

    returns

    true if this sequence contains a slice with the same elements as that, otherwise false.

    Definition Classes
    SeqOps
  35. def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Int

    Copy elements to an array, returning the number of elements written.

    Copy elements to an array, returning the number of elements written.

    Fills the given array xs starting at index start with at most len elements of this collection.

    Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached, or len elements have been copied.

    B

    the type of the elements of the array.

    xs

    the array to fill.

    start

    the starting index of xs.

    len

    the maximal number of elements to copy.

    returns

    the number of elements written to the array

    Definition Classes
    IterableOnceOps
    Note

    Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change. Note: will not terminate for infinite-sized collections.

  36. def copyToArray[B >: A](xs: Array[B], start: Int): Int

    Copy elements to an array, returning the number of elements written.

    Copy elements to an array, returning the number of elements written.

    Fills the given array xs starting at index start with values of this collection.

    Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.

    B

    the type of the elements of the array.

    xs

    the array to fill.

    start

    the starting index of xs.

    returns

    the number of elements written to the array Note: will not terminate for infinite-sized collections.

    Definition Classes
    IterableOnceOps
  37. def copyToArray[B >: A](xs: Array[B]): Int

    Copy elements to an array, returning the number of elements written.

    Copy elements to an array, returning the number of elements written.

    Fills the given array xs starting at index start with values of this collection.

    Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.

    B

    the type of the elements of the array.

    xs

    the array to fill.

    returns

    the number of elements written to the array Note: will not terminate for infinite-sized collections.

    Definition Classes
    IterableOnceOps
  38. def corresponds[B](that: collection.Seq[B])(p: (A, B) => Boolean): Boolean

    Tests whether every element of this sequence relates to the corresponding element of another sequence by satisfying a test predicate.

    Tests whether every element of this sequence relates to the corresponding element of another sequence by satisfying a test predicate.

    B

    the type of the elements of that

    that

    the other sequence

    p

    the test predicate, which relates elements from both sequences

    returns

    true if both sequences have the same length and p(x, y) is true for all corresponding elements x of this sequence and y of that, otherwise false.

    Definition Classes
    SeqOps
  39. def corresponds[B](that: IterableOnce[B])(p: (A, B) => Boolean): Boolean

    Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.

    Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.

    Note: will not terminate for infinite-sized collections.

    B

    the type of the elements of that

    that

    the other collection

    p

    the test predicate, which relates elements from both collections

    returns

    true if both collections have the same length and p(x, y) is true for all corresponding elements x of this iterator and y of that, otherwise false

    Definition Classes
    IterableOnceOps
  40. def count(p: (A) => Boolean): Int

    Counts the number of elements in the collection which satisfy a predicate.

    Counts the number of elements in the collection which satisfy a predicate.

    Note: will not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    the number of elements satisfying the predicate p.

    Definition Classes
    IterableOnceOps
  41. def diff[B >: A](that: collection.Seq[B]): LazyList[A]

    Computes the multiset difference between this lazy list and another sequence.

    Computes the multiset difference between this lazy list and another sequence.

    This method preserves laziness; elements are only evaluated individually as needed.

    that

    the sequence of elements to remove

    returns

    a new lazy list which contains all elements of this lazy list except some of occurrences of elements that also appear in that. If an element value x appears n times in that, then the first n occurrences of x will not form part of the result, but any following occurrences will.

    Definition Classes
    LazyListSeqOps
  42. def distinct: LazyList[A]

    Selects all the elements of this sequence ignoring the duplicates.

    Selects all the elements of this sequence ignoring the duplicates.

    returns

    a new sequence consisting of all the elements of this sequence without duplicates.

    Definition Classes
    SeqOps
  43. def distinctBy[B](f: (A) => B): LazyList[A]

    Selects all the elements of this sequence ignoring the duplicates as determined by == after applying the transforming function f.

    Selects all the elements of this sequence ignoring the duplicates as determined by == after applying the transforming function f.

    B

    the type of the elements after being transformed by f

    f

    The transforming function whose result is used to determine the uniqueness of each element

    returns

    a new sequence consisting of all the elements of this sequence without duplicates.

    Definition Classes
    SeqOps
  44. def drop(n: Int): LazyList[A]

    Selects all elements except first n ones.

    Selects all elements except first n ones.

    This method does not evaluate anything until an operation is performed on the result (e.g. calling head or tail, or checking if it is empty). Additionally, it preserves laziness for all except the first n elements.

    n

    the number of elements to drop from this lazy list.

    returns

    a lazy list consisting of all elements of this lazy list except the first n ones, or else the empty lazy list, if this lazy list has less than n elements. If n is negative, don't drop any elements.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  45. def dropRight(n: Int): LazyList[A]

    Selects all elements except last n ones.

    Selects all elements except last n ones.

    This method does not evaluate anything until an operation is performed on the result (e.g. calling head or tail, or checking if it is empty).

    n

    the number of elements to drop from this lazy list.

    returns

    a lazy list consisting of all elements of this lazy list except the last n ones, or else the empty lazy list, if this lazy list has less than n elements. If n is negative, don't drop any elements.

    Definition Classes
    LazyListIterableOps
  46. def dropWhile(p: (A) => Boolean): LazyList[A]

    Drops longest prefix of elements that satisfy a predicate.

    Drops longest prefix of elements that satisfy a predicate.

    This method does not evaluate anything until an operation is performed on the result (e.g. calling head or tail, or checking if it is empty). Additionally, it preserves laziness for all elements after the predicate returns false.

    p

    The predicate used to test elements.

    returns

    the longest suffix of this lazy list whose first element does not satisfy the predicate p.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  47. def elementWise: ElementWiseExtractor[Int, A]

    Returns an extractor object with a unapplySeq method, which extracts each element of a sequence data.

    Returns an extractor object with a unapplySeq method, which extracts each element of a sequence data.

    Definition Classes
    PartialFunction
    Example:
    1. val firstChar: String => Option[Char] = _.headOption
      
      Seq("foo", "bar", "baz") match {
        case firstChar.unlift.elementWise(c0, c1, c2) =>
          println(s"$c0, $c1, $c2") // Output: f, b, b
      }
  48. def empty: LazyList[A]

    The empty iterable of the same type as this iterable

    The empty iterable of the same type as this iterable

    returns

    an empty iterable of type C.

    Definition Classes
    IterableFactoryDefaultsIterableOps
  49. def endsWith[B >: A](that: collection.Iterable[B]): Boolean

    Tests whether this sequence ends with the given sequence.

    Tests whether this sequence ends with the given sequence.

    Note: will not terminate for infinite-sized collections.

    that

    the sequence to test

    returns

    true if this sequence has that as a suffix, false otherwise.

    Definition Classes
    SeqOps
  50. def ensuring(cond: (LazyList[A]) => Boolean, msg: => Any): LazyList[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toEnsuring[LazyList[A]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  51. def ensuring(cond: (LazyList[A]) => Boolean): LazyList[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toEnsuring[LazyList[A]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  52. def ensuring(cond: Boolean, msg: => Any): LazyList[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toEnsuring[LazyList[A]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  53. def ensuring(cond: Boolean): LazyList[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toEnsuring[LazyList[A]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  54. final def eq(arg0: AnyRef): Boolean

    Tests whether the argument (that) is a reference to the receiver object (this).

    Tests whether the argument (that) is a reference to the receiver object (this).

    The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

    returns

    true if the argument is a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef
  55. def equals(that: Any): Boolean

    The universal equality method defined in AnyRef.

    The universal equality method defined in AnyRef.

    This method evaluates all elements of the collection.

    Definition Classes
    LazyListSeqEquals → AnyRef → Any
  56. def exists(p: (A) => Boolean): Boolean

    Tests whether a predicate holds for at least one element of this sequence.

    Tests whether a predicate holds for at least one element of this sequence.

    Note: may not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    true if the given predicate p is satisfied by at least one element of this sequence, otherwise false

    Definition Classes
    LinearSeqOpsIterableOnceOps
  57. def filter(pred: (A) => Boolean): LazyList[A]

    Selects all elements of this lazy list which satisfy a predicate.

    Selects all elements of this lazy list which satisfy a predicate.

    This method preserves laziness; elements are only evaluated individually as needed.

    returns

    a new iterator consisting of all elements of this lazy list that satisfy the given predicate p. The order of the elements is preserved.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  58. def filterNot(pred: (A) => Boolean): LazyList[A]

    Selects all elements of this lazy list which do not satisfy a predicate.

    Selects all elements of this lazy list which do not satisfy a predicate.

    This method preserves laziness; elements are only evaluated individually as needed.

    pred

    the predicate used to test elements.

    returns

    a new lazy list consisting of all elements of this lazy list that do not satisfy the given predicate pred. Their order may not be preserved.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  59. def finalize(): Unit

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.Throwable])
    Note

    not specified by SLS as a member of AnyRef

  60. def find(p: (A) => Boolean): Option[A]

    Finds the first element of the lazy list satisfying a predicate, if any.

    Finds the first element of the lazy list satisfying a predicate, if any.

    Note: may not terminate for infinite-sized collections.

    This method does not evaluate any elements further than the first element matching the predicate.

    p

    the predicate used to test elements.

    returns

    an option value containing the first element in the lazy list that satisfies p, or None if none exists.

    Definition Classes
    LazyListLinearSeqOpsIterableOnceOps
    Annotations
    @tailrec()
  61. def findLast(p: (A) => Boolean): Option[A]

    Finds the last element of the sequence satisfying a predicate, if any.

    Finds the last element of the sequence satisfying a predicate, if any.

    Note: will not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    an option value containing the last element in the sequence that satisfies p, or None if none exists.

    Definition Classes
    LinearSeqOpsSeqOps
  62. def flatMap[B](f: (A) => IterableOnce[B]): LazyList[B]

    Builds a new lazy list by applying a function to all elements of this lazy list and using the elements of the resulting collections.

    Builds a new lazy list by applying a function to all elements of this lazy list and using the elements of the resulting collections.

    For example:

    def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+")

    The type of the resulting collection is guided by the static type of lazy list. This might cause unexpected results sometimes. For example:

    // lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set
    def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet)
    
    // lettersOf will return a Set[Char], not a Seq
    def lettersOf(words: Seq[String]) = words.toSet flatMap ((word: String) => word.toSeq)
    
    // xs will be an Iterable[Int]
    val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2)
    
    // ys will be a Map[Int, Int]
    val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the element type of the returned collection.

    f

    the function to apply to each element.

    returns

    a new lazy list resulting from applying the given collection-valued function f to each element of this lazy list and concatenating the results.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  63. def flatten[B](implicit asIterable: (A) => IterableOnce[B]): LazyList[B]

    Converts this lazy list of traversable collections into a lazy list formed by the elements of these traversable collections.

    Converts this lazy list of traversable collections into a lazy list formed by the elements of these traversable collections.

    The resulting collection's type will be guided by the type of lazy list. For example:

    val xs = List(
               Set(1, 2, 3),
               Set(1, 2, 3)
             ).flatten
    // xs == List(1, 2, 3, 1, 2, 3)
    
    val ys = Set(
               List(1, 2, 3),
               List(3, 2, 1)
             ).flatten
    // ys == Set(1, 2, 3)

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the type of the elements of each traversable collection.

    asIterable

    an implicit conversion which asserts that the element type of this lazy list is a GenTraversable.

    returns

    a new lazy list resulting from concatenating all element lazy lists.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  64. def fold[A1 >: A](z: A1)(op: (A1, A1) => A1): A1

    Folds the elements of this collection using the specified associative binary operator.

    Folds the elements of this collection using the specified associative binary operator. The default implementation in IterableOnce is equivalent to foldLeft but may be overridden for more efficient traversal orders.

    The order in which operations are performed on elements is unspecified and may be nondeterministic.

    Note: will not terminate for infinite-sized collections.

    A1

    a type parameter for the binary operator, a supertype of A.

    z

    a neutral element for the fold operation; may be added to the result an arbitrary number of times, and must not change the result (e.g., Nil for list concatenation, 0 for addition, or 1 for multiplication).

    op

    a binary operator that must be associative.

    returns

    the result of applying the fold operator op between all the elements and z, or z if this collection is empty.

    Definition Classes
    IterableOnceOps
  65. def foldLeft[B](z: B)(op: (B, A) => B): B

    LazyList specialization of foldLeft which allows GC to collect along the way.

    LazyList specialization of foldLeft which allows GC to collect along the way.

    B

    The type of value being accumulated.

    z

    The initial value seeded into the function op.

    op

    The operation to perform on successive elements of the LazyList.

    returns

    The accumulated value from successive applications of op.

    Definition Classes
    LazyListLinearSeqOpsIterableOnceOps
    Annotations
    @tailrec()
  66. def foldRight[B](z: B)(op: (A, B) => B): B

    Applies a binary operator to all elements of this collection and a start value, going right to left.

    Applies a binary operator to all elements of this collection and a start value, going right to left.

    Note: will not terminate for infinite-sized collections.

    Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

    B

    the result type of the binary operator.

    z

    the start value.

    op

    the binary operator.

    returns

    the result of inserting op between consecutive elements of this collection, going right to left with the start value z on the right:

    op(x_1, op(x_2, ... op(x_n, z)...))

    where x1, ..., xn are the elements of this collection. Returns z if this collection is empty.

    Definition Classes
    IterableOnceOps
  67. def forall(p: (A) => Boolean): Boolean

    Tests whether a predicate holds for all elements of this sequence.

    Tests whether a predicate holds for all elements of this sequence.

    Note: may not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    true if this sequence is empty or the given predicate p holds for all elements of this sequence, otherwise false.

    Definition Classes
    LinearSeqOpsIterableOnceOps
  68. def force: LazyList.this.type

    Evaluates all undefined elements of the lazy list.

    Evaluates all undefined elements of the lazy list.

    This method detects cycles in lazy lists, and terminates after all elements of the cycle are evaluated. For example:

    val ring: LazyList[Int] = 1 #:: 2 #:: 3 #:: ring
    ring.force
    ring.toString
    
    // prints
    //
    // LazyList(1, 2, 3, ...)

    This method will *not* terminate for non-cyclic infinite-sized collections.

    returns

    this

  69. def foreach[U](f: (A) => U): Unit

    Apply the given function f to each element of this linear sequence (while respecting the order of the elements).

    Apply the given function f to each element of this linear sequence (while respecting the order of the elements).

    f

    The treatment to apply to each element.

    Definition Classes
    LazyListLinearSeqOpsIterableOnceOps
    Annotations
    @tailrec()
    Note

    Overridden here as final to trigger tail-call optimization, which replaces 'this' with 'tail' at each iteration. This is absolutely necessary for allowing the GC to collect the underlying LazyList as elements are consumed.

    ,

    This function will force the realization of the entire LazyList unless the f throws an exception.

  70. def formatted(fmtstr: String): String

    Returns string formatted according to given format string.

    Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).

    Implicit
    This member is added by an implicit conversion from LazyList[A] toStringFormat[LazyList[A]] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  71. def fromSpecific(coll: IterableOnce[A]): LazyList[A]

    Defines how to turn a given Iterable[A] into a collection of type C.

    Defines how to turn a given Iterable[A] into a collection of type C.

    This process can be done in a strict way or a non-strict way (ie. without evaluating the elements of the resulting collections). In other words, this methods defines the evaluation model of the collection.

    Attributes
    protected
    Definition Classes
    IterableFactoryDefaultsIterableOps
    Note

    When implementing a custom collection type and refining C to the new type, this method needs to be overridden (the compiler will issue an error otherwise). In the common case where C =:= CC[A], this can be done by mixing in the scala.collection.IterableFactoryDefaults trait, which implements the method using iterableFactory.

    ,

    As witnessed by the @uncheckedVariance annotation, using this method might be unsound. However, as long as it is called with an Iterable[A] obtained from this collection (as it is the case in the implementations of operations where we use a View[A]), it is safe.

  72. final def getClass(): Class[_ <: AnyRef]

    Returns the runtime class representation of the object.

    Returns the runtime class representation of the object.

    returns

    a class object corresponding to the runtime type of the receiver.

    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  73. def groupBy[K](f: (A) => K): Map[K, LazyList[A]]

    Partitions this iterable collection into a map of iterable collections according to some discriminator function.

    Partitions this iterable collection into a map of iterable collections according to some discriminator function.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    K

    the type of keys returned by the discriminator function.

    f

    the discriminator function.

    returns

    A map from keys to iterable collections such that the following invariant holds:

    (xs groupBy f)(k) = xs filter (x => f(x) == k)

    That is, every key k is bound to a iterable collection of those elements x for which f(x) equals k.

    Definition Classes
    IterableOps
  74. def groupMap[K, B](key: (A) => K)(f: (A) => B): Map[K, LazyList[B]]

    Partitions this iterable collection into a map of iterable collections according to a discriminator function key.

    Partitions this iterable collection into a map of iterable collections according to a discriminator function key. Each element in a group is transformed into a value of type B using the value function.

    It is equivalent to groupBy(key).mapValues(_.map(f)), but more efficient.

    case class User(name: String, age: Int)
    
    def namesByAge(users: Seq[User]): Map[Int, Seq[String]] =
      users.groupMap(_.age)(_.name)

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    K

    the type of keys returned by the discriminator function

    B

    the type of values returned by the transformation function

    key

    the discriminator function

    f

    the element transformation function

    Definition Classes
    IterableOps
  75. def groupMapReduce[K, B](key: (A) => K)(f: (A) => B)(reduce: (B, B) => B): Map[K, B]

    Partitions this iterable collection into a map according to a discriminator function key.

    Partitions this iterable collection into a map according to a discriminator function key. All the values that have the same discriminator are then transformed by the value function and then reduced into a single value with the reduce function.

    It is equivalent to groupBy(key).mapValues(_.map(f).reduce(reduce)), but more efficient.

    def occurrences[A](as: Seq[A]): Map[A, Int] =
      as.groupMapReduce(identity)(_ => 1)(_ + _)

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    Definition Classes
    IterableOps
  76. def grouped(size: Int): Iterator[LazyList[A]]

    Partitions elements in fixed size lazy lists.

    Partitions elements in fixed size lazy lists.

    The iterator returned by this method mostly preserves laziness; a single element ahead of the iterator is evaluated.

    size

    the number of elements per group

    returns

    An iterator producing lazy lists of size size, except the last will be less than size size if the elements don't divide evenly.

    Definition Classes
    LazyListIterableOps
  77. def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

    the hash code value for this object.

    Definition Classes
    Seq → AnyRef → Any
  78. def head: A

    Selects the first element of this lazy list.

    Selects the first element of this lazy list.

    returns

    the first element of this lazy list.

    Definition Classes
    LazyListLinearSeqOpsIterableOps
    Exceptions thrown

    NoSuchElementException if the lazy list is empty.

  79. def headOption: Option[A]

    Optionally selects the first element.

    Optionally selects the first element.

    returns

    the first element of this sequence if it is nonempty, None if it is empty.

    Definition Classes
    LinearSeqOpsIterableOps
  80. def indexOf[B >: A](elem: B): Int

    Finds index of first occurrence of some value in this sequence.

    Finds index of first occurrence of some value in this sequence.

    B

    the type of the element elem.

    elem

    the element value to search for.

    returns

    the index >= 0 of the first element of this sequence that is equal (as determined by ==) to elem, or -1, if none exists.

    Definition Classes
    SeqOps
    Annotations
    @deprecatedOverriding(message = "Override indexOf(elem, from) instead - indexOf(elem) calls indexOf(elem, 0)", since = "2.13.0")
  81. def indexOf[B >: A](elem: B, from: Int): Int

    Finds index of first occurrence of some value in this sequence after or at some start index.

    Finds index of first occurrence of some value in this sequence after or at some start index.

    B

    the type of the element elem.

    elem

    the element value to search for.

    from

    the start index

    returns

    the index >= from of the first element of this sequence that is equal (as determined by ==) to elem, or -1, if none exists.

    Definition Classes
    SeqOps
  82. def indexOfSlice[B >: A](that: collection.Seq[B]): Int

    Finds first index where this sequence contains a given sequence as a slice.

    Finds first index where this sequence contains a given sequence as a slice.

    Note: may not terminate for infinite-sized collections.

    that

    the sequence to test

    returns

    the first index >= 0 such that the elements of this sequence starting at this index match the elements of sequence that, or -1 of no such subsequence exists.

    Definition Classes
    SeqOps
    Annotations
    @deprecatedOverriding(message = "Override indexOfSlice(that, from) instead - indexOfSlice(that) calls indexOfSlice(that, 0)", since = "2.13.0")
  83. def indexOfSlice[B >: A](that: collection.Seq[B], from: Int): Int

    Finds first index after or at a start index where this sequence contains a given sequence as a slice.

    Finds first index after or at a start index where this sequence contains a given sequence as a slice.

    Note: may not terminate for infinite-sized collections.

    that

    the sequence to test

    from

    the start index

    returns

    the first index >= from such that the elements of this sequence starting at this index match the elements of sequence that, or -1 of no such subsequence exists.

    Definition Classes
    SeqOps
  84. def indexWhere(p: (A) => Boolean, from: Int): Int

    Finds index of the first element satisfying some predicate after or at some start index.

    Finds index of the first element satisfying some predicate after or at some start index.

    Note: may not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    from

    the start index

    returns

    the index >= from of the first element of this sequence that satisfies the predicate p, or -1, if none exists.

    Definition Classes
    LinearSeqOpsSeqOps
  85. def indexWhere(p: (A) => Boolean): Int

    Finds index of the first element satisfying some predicate.

    Finds index of the first element satisfying some predicate.

    Note: may not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    the index >= 0 of the first element of this sequence that satisfies the predicate p, or -1, if none exists.

    Definition Classes
    SeqOps
    Annotations
    @deprecatedOverriding(message = "Override indexWhere(p, from) instead - indexWhere(p) calls indexWhere(p, 0)", since = "2.13.0")
  86. def indices: Range

    Produces the range of all indices of this sequence.

    Produces the range of all indices of this sequence.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    returns

    a Range value from 0 to one less than the length of this sequence.

    Definition Classes
    SeqOps
  87. def init: LazyList[A]

    The initial part of the collection without its last element.

    The initial part of the collection without its last element.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    Definition Classes
    IterableOps
  88. def inits: Iterator[LazyList[A]]

    Iterates over the inits of this iterable collection.

    Iterates over the inits of this iterable collection. The first value will be this iterable collection and the final one will be an empty iterable collection, with the intervening values the results of successive applications of init.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    returns

    an iterator over all the inits of this iterable collection

    Definition Classes
    IterableOps
    Example:
    1. List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)

  89. def intersect[B >: A](that: collection.Seq[B]): LazyList[A]

    Computes the multiset intersection between this lazy list and another sequence.

    Computes the multiset intersection between this lazy list and another sequence.

    This method preserves laziness; elements are only evaluated individually as needed.

    that

    the sequence of elements to intersect with.

    returns

    a new lazy list which contains all elements of this lazy list which also appear in that. If an element value x appears n times in that, then the first n occurrences of x will be retained in the result, but any following occurrences will be omitted.

    Definition Classes
    LazyListSeqOps
  90. def isDefinedAt(x: Int): Boolean

    Tests whether this sequence contains given index.

    Tests whether this sequence contains given index.

    The implementations of methods apply and isDefinedAt turn a Seq[A] into a PartialFunction[Int, A].

    returns

    true if this sequence contains an element at position idx, false otherwise.

    Definition Classes
    LinearSeqOpsSeqOps
  91. def isEmpty: Boolean

    Tests whether the lazy list is empty.

    Tests whether the lazy list is empty.

    Note: Implementations in subclasses that are not repeatedly traversable must take care not to consume any elements when isEmpty is called.

    returns

    true if the lazy list contains no elements, false otherwise.

    Definition Classes
    LazyListLinearSeqOpsSeqOpsIterableOnceOps
  92. final def isInstanceOf[T0]: Boolean

    Test whether the dynamic type of the receiver object is T0.

    Test whether the dynamic type of the receiver object is T0.

    Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

    returns

    true if the receiver object is an instance of erasure of type T0; false otherwise.

    Definition Classes
    Any
  93. def isTraversableAgain: Boolean

    Tests whether this iterable collection can be repeatedly traversed.

    Tests whether this iterable collection can be repeatedly traversed. Always true for Iterables and false for Iterators unless overridden.

    returns

    true if it is repeatedly traversable, false otherwise.

    Definition Classes
    IterableOpsIterableOnceOps
  94. def iterableFactory: SeqFactory[LazyList]

    The companion object of this lazy list, providing various factory methods.

    The companion object of this lazy list, providing various factory methods.

    Definition Classes
    LazyListLinearSeqLinearSeqSeqIterableSeqIterableIterableOps
    Note

    When implementing a custom collection type and refining CC to the new type, this method needs to be overridden to return a factory for the new type (the compiler will issue an error otherwise).

  95. def iterator: Iterator[A]

    Iterator can be used only once

    Iterator can be used only once

    The iterator returned by this method preserves laziness; elements are only evaluated individually as needed.

    Definition Classes
    LazyListLinearSeqOpsIterableOnce
  96. def knownSize: Int

    This method preserves laziness; elements are only evaluated individually as needed.

    This method preserves laziness; elements are only evaluated individually as needed.

    returns

    The number of elements in this lazy list, if it can be cheaply computed, -1 otherwise. Cheaply usually means: Not requiring a collection traversal.

    Definition Classes
    LazyListIterableOnce
  97. def last: A

    Selects the last element.

    Selects the last element.

    returns

    The last element of this sequence.

    Definition Classes
    LinearSeqOpsIterableOps
    Exceptions thrown

    NoSuchElementException If the sequence is empty.

  98. def lastIndexOf[B >: A](elem: B, end: Int = length - 1): Int

    Finds index of last occurrence of some value in this sequence before or at a given end index.

    Finds index of last occurrence of some value in this sequence before or at a given end index.

    Note: will not terminate for infinite-sized collections.

    B

    the type of the element elem.

    elem

    the element value to search for.

    end

    the end index.

    returns

    the index <= end of the last element of this sequence that is equal (as determined by ==) to elem, or -1, if none exists.

    Definition Classes
    SeqOps
  99. def lastIndexOfSlice[B >: A](that: collection.Seq[B]): Int

    Finds last index where this sequence contains a given sequence as a slice.

    Finds last index where this sequence contains a given sequence as a slice.

    Note: will not terminate for infinite-sized collections.

    that

    the sequence to test

    returns

    the last index such that the elements of this sequence starting at this index match the elements of sequence that, or -1 of no such subsequence exists.

    Definition Classes
    SeqOps
    Annotations
    @deprecatedOverriding(message = "Override lastIndexOfSlice(that, end) instead - lastIndexOfSlice(that) calls lastIndexOfSlice(that, Int.MaxValue)", since = "2.13.0")
  100. def lastIndexOfSlice[B >: A](that: collection.Seq[B], end: Int): Int

    Finds last index before or at a given end index where this sequence contains a given sequence as a slice.

    Finds last index before or at a given end index where this sequence contains a given sequence as a slice.

    Note: will not terminate for infinite-sized collections.

    that

    the sequence to test

    end

    the end index

    returns

    the last index <= end such that the elements of this sequence starting at this index match the elements of sequence that, or -1 of no such subsequence exists.

    Definition Classes
    SeqOps
  101. def lastIndexWhere(p: (A) => Boolean, end: Int): Int

    Finds index of last element satisfying some predicate before or at given end index.

    Finds index of last element satisfying some predicate before or at given end index.

    Note: will not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    the index <= end of the last element of this sequence that satisfies the predicate p, or -1, if none exists.

    Definition Classes
    LinearSeqOpsSeqOps
  102. def lastIndexWhere(p: (A) => Boolean): Int

    Finds index of last element satisfying some predicate.

    Finds index of last element satisfying some predicate.

    Note: will not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    the index of the last element of this sequence that satisfies the predicate p, or -1, if none exists.

    Definition Classes
    SeqOps
    Annotations
    @deprecatedOverriding(message = "Override lastIndexWhere(p, end) instead - lastIndexWhere(p) calls lastIndexWhere(p, Int.MaxValue)", since = "2.13.0")
  103. def lastOption: Option[A]

    Optionally selects the last element.

    Optionally selects the last element.

    Note: might return different results for different runs, unless the underlying collection type is ordered.

    returns

    the last element of this iterable collection$ if it is nonempty, None if it is empty.

    Definition Classes
    IterableOps
  104. def lazyAppendedAll[B >: A](suffix: => IterableOnce[B]): LazyList[B]

    The lazy list resulting from the concatenation of this lazy list with the argument lazy list.

    The lazy list resulting from the concatenation of this lazy list with the argument lazy list.

    This method preserves laziness; elements are only evaluated individually as needed.

    Note: Repeated chaining of calls to append methods (appended, appendedAll, lazyAppendedAll) without forcing any of the intermediate resulting lazy lists may overflow the stack when the final result is forced.

    suffix

    The collection that gets appended to this lazy list

    returns

    The lazy list containing elements of this lazy list and the iterable object.

  105. def lazyZip[B](that: collection.Iterable[B]): LazyZip2[A, B, LazyList.this.type]

    Analogous to zip except that the elements in each collection are not consumed until a strict operation is invoked on the returned LazyZip2 decorator.

    Analogous to zip except that the elements in each collection are not consumed until a strict operation is invoked on the returned LazyZip2 decorator.

    Calls to lazyZip can be chained to support higher arities (up to 4) without incurring the expense of constructing and deconstructing intermediary tuples.

    val xs = List(1, 2, 3)
    val res = (xs lazyZip xs lazyZip xs lazyZip xs).map((a, b, c, d) => a + b + c + d)
    // res == List(4, 8, 12)

    This method is not particularly useful for a lazy list, as zip already preserves laziness.

    The collection.LazyZip2 returned by this method preserves laziness; elements are only evaluated individually as needed.

    B

    the type of the second element in each eventual pair

    that

    the iterable providing the second element of each eventual pair

    returns

    a decorator LazyZip2 that allows strict operations to be performed on the lazily evaluated pairs or chained calls to lazyZip. Implicit conversion to Iterable[(A, B)] is also supported.

    Definition Classes
    LazyListIterable
  106. def length: Int

    The length (number of elements) of the sequence.

    The length (number of elements) of the sequence. size is an alias for length in Seq collections.

    Definition Classes
    LinearSeqOpsSeqOps
  107. def lengthCompare(that: collection.Iterable[_]): Int

    Compares the length of this sequence to the size of another Iterable.

    Compares the length of this sequence to the size of another Iterable.

    that

    the Iterable whose size is compared with this sequence's length.

    returns

    A value x where

    x <  0       if this.length <  that.size
    x == 0       if this.length == that.size
    x >  0       if this.length >  that.size

    The method as implemented here does not call length or size directly; its running time is O(this.length min that.size) instead of O(this.length + that.size). The method should be overridden if computing size is cheap and knownSize returns -1.

    Definition Classes
    LinearSeqOpsSeqOps
  108. def lengthCompare(len: Int): Int

    Compares the length of this sequence to a test value.

    Compares the length of this sequence to a test value.

    len

    the test value that gets compared with the length.

    returns

    A value x where

    x <  0       if this.length <  len
    x == 0       if this.length == len
    x >  0       if this.length >  len

    The method as implemented here does not call length directly; its running time is O(length min len) instead of O(length). The method should be overridden if computing length is cheap and knownSize returns -1.

    Definition Classes
    LinearSeqOpsSeqOps
    See also

    lengthIs

  109. final def lengthIs: SizeCompareOps

    Returns a value class containing operations for comparing the length of this sequence to a test value.

    Returns a value class containing operations for comparing the length of this sequence to a test value.

    These operations are implemented in terms of lengthCompare(Int), and allow the following more readable usages:

    this.lengthIs < len     // this.lengthCompare(len) < 0
    this.lengthIs <= len    // this.lengthCompare(len) <= 0
    this.lengthIs == len    // this.lengthCompare(len) == 0
    this.lengthIs != len    // this.lengthCompare(len) != 0
    this.lengthIs >= len    // this.lengthCompare(len) >= 0
    this.lengthIs > len     // this.lengthCompare(len) > 0
    Definition Classes
    SeqOps
    Annotations
    @inline()
  110. def lift: (Int) => Option[A]

    Turns this partial function into a plain function returning an Option result.

    Turns this partial function into a plain function returning an Option result.

    returns

    a function that takes an argument x to Some(this(x)) if this is defined for x, and to None otherwise.

    Definition Classes
    PartialFunction
    See also

    Function.unlift

  111. def map[B](f: (A) => B): LazyList[B]

    Builds a new lazy list by applying a function to all elements of this lazy list.

    Builds a new lazy list by applying a function to all elements of this lazy list.

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the element type of the returned lazy list.

    f

    the function to apply to each element.

    returns

    a new lazy list resulting from applying the given function f to each element of this lazy list and collecting the results.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  112. def max[B >: A](implicit ord: math.Ordering[B]): A

    Finds the largest element.

    Finds the largest element.

    Note: will not terminate for infinite-sized collections.

    B

    The type over which the ordering is defined.

    ord

    An ordering to be used for comparing elements.

    returns

    the largest element of this collection with respect to the ordering ord.

    Definition Classes
    IterableOnceOps
    Exceptions thrown

    UnsupportedOperationException if this collection is empty.

  113. def maxBy[B](f: (A) => B)(implicit cmp: math.Ordering[B]): A

    Finds the first element which yields the largest value measured by function f.

    Finds the first element which yields the largest value measured by function f.

    Note: will not terminate for infinite-sized collections.

    B

    The result type of the function f.

    f

    The measuring function.

    cmp

    An ordering to be used for comparing elements.

    returns

    the first element of this collection with the largest value measured by function f with respect to the ordering cmp.

    Definition Classes
    IterableOnceOps
    Exceptions thrown

    UnsupportedOperationException if this collection is empty.

  114. def maxByOption[B](f: (A) => B)(implicit cmp: math.Ordering[B]): Option[A]

    Finds the first element which yields the largest value measured by function f.

    Finds the first element which yields the largest value measured by function f.

    Note: will not terminate for infinite-sized collections.

    B

    The result type of the function f.

    f

    The measuring function.

    cmp

    An ordering to be used for comparing elements.

    returns

    an option value containing the first element of this collection with the largest value measured by function f with respect to the ordering cmp.

    Definition Classes
    IterableOnceOps
  115. def maxOption[B >: A](implicit ord: math.Ordering[B]): Option[A]

    Finds the largest element.

    Finds the largest element.

    Note: will not terminate for infinite-sized collections.

    B

    The type over which the ordering is defined.

    ord

    An ordering to be used for comparing elements.

    returns

    an option value containing the largest element of this collection with respect to the ordering ord.

    Definition Classes
    IterableOnceOps
  116. def min[B >: A](implicit ord: math.Ordering[B]): A

    Finds the smallest element.

    Finds the smallest element.

    Note: will not terminate for infinite-sized collections.

    B

    The type over which the ordering is defined.

    ord

    An ordering to be used for comparing elements.

    returns

    the smallest element of this collection with respect to the ordering ord.

    Definition Classes
    IterableOnceOps
    Exceptions thrown

    UnsupportedOperationException if this collection is empty.

  117. def minBy[B](f: (A) => B)(implicit cmp: math.Ordering[B]): A

    Finds the first element which yields the smallest value measured by function f.

    Finds the first element which yields the smallest value measured by function f.

    Note: will not terminate for infinite-sized collections.

    B

    The result type of the function f.

    f

    The measuring function.

    cmp

    An ordering to be used for comparing elements.

    returns

    the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.

    Definition Classes
    IterableOnceOps
    Exceptions thrown

    UnsupportedOperationException if this collection is empty.

  118. def minByOption[B](f: (A) => B)(implicit cmp: math.Ordering[B]): Option[A]

    Finds the first element which yields the smallest value measured by function f.

    Finds the first element which yields the smallest value measured by function f.

    Note: will not terminate for infinite-sized collections.

    B

    The result type of the function f.

    f

    The measuring function.

    cmp

    An ordering to be used for comparing elements.

    returns

    an option value containing the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.

    Definition Classes
    IterableOnceOps
  119. def minOption[B >: A](implicit ord: math.Ordering[B]): Option[A]

    Finds the smallest element.

    Finds the smallest element.

    Note: will not terminate for infinite-sized collections.

    B

    The type over which the ordering is defined.

    ord

    An ordering to be used for comparing elements.

    returns

    an option value containing the smallest element of this collection with respect to the ordering ord.

    Definition Classes
    IterableOnceOps
  120. final def mkString: String

    Displays all elements of this collection in a string.

    Displays all elements of this collection in a string.

    Delegates to addString, which can be overridden.

    returns

    a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection follow each other without any separator string.

    Definition Classes
    IterableOnceOps
    Annotations
    @inline()
  121. final def mkString(sep: String): String

    Displays all elements of this collection in a string using a separator string.

    Displays all elements of this collection in a string using a separator string.

    Delegates to addString, which can be overridden.

    sep

    the separator string.

    returns

    a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection are separated by the string sep.

    Definition Classes
    IterableOnceOps
    Annotations
    @inline()
    Example:
    1. List(1, 2, 3).mkString("|") = "1|2|3"

  122. final def mkString(start: String, sep: String, end: String): String

    Displays all elements of this collection in a string using start, end, and separator strings.

    Displays all elements of this collection in a string using start, end, and separator strings.

    Delegates to addString, which can be overridden.

    start

    the starting string.

    sep

    the separator string.

    end

    the ending string.

    returns

    a string representation of this collection. The resulting string begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this collection are separated by the string sep.

    Definition Classes
    IterableOnceOps
    Example:
    1. List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"

  123. final def ne(arg0: AnyRef): Boolean

    Equivalent to !(this eq that).

    Equivalent to !(this eq that).

    returns

    true if the argument is not a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef
  124. def newSpecificBuilder: Builder[A, LazyList[A]]

    returns

    a strict builder for the same collection type. Note that in the case of lazy collections (e.g. scala.collection.View or scala.collection.immutable.LazyList), it is possible to implement this method but the resulting Builder will break laziness. As a consequence, operations should preferably be implemented with fromSpecific instead of this method.

    Attributes
    protected
    Definition Classes
    IterableFactoryDefaultsIterableOps
    Note

    When implementing a custom collection type and refining C to the new type, this method needs to be overridden (the compiler will issue an error otherwise). In the common case where C =:= CC[A], this can be done by mixing in the scala.collection.IterableFactoryDefaults trait, which implements the method using iterableFactory.

    ,

    As witnessed by the @uncheckedVariance annotation, using this method might be unsound. However, as long as the returned builder is only fed with A values taken from this instance, it is safe.

  125. def nonEmpty: Boolean

    Tests whether the collection is not empty.

    Tests whether the collection is not empty.

    returns

    true if the collection contains at least one element, false otherwise.

    Definition Classes
    IterableOnceOps
    Annotations
    @deprecatedOverriding(message = "nonEmpty is defined as !isEmpty; override isEmpty instead", since = "2.13.0")
  126. final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  127. final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  128. def occCounts[B](sq: collection.Seq[B]): mutable.Map[B, Int]
    Attributes
    protected[collection]
    Definition Classes
    SeqOps
  129. def orElse[A1 <: Int, B1 >: A](that: PartialFunction[A1, B1]): PartialFunction[A1, B1]

    Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.

    Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.

    A1

    the argument type of the fallback function

    B1

    the result type of the fallback function

    that

    the fallback function

    returns

    a partial function which has as domain the union of the domains of this partial function and that. The resulting partial function takes x to this(x) where this is defined, and to that(x) where it is not.

    Definition Classes
    PartialFunction
  130. def padTo[B >: A](len: Int, elem: B): LazyList[B]

    A copy of this lazy list with an element value appended until a given target length is reached.

    A copy of this lazy list with an element value appended until a given target length is reached.

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the element type of the returned lazy list.

    len

    the target length

    elem

    the padding value

    returns

    a new lazy list consisting of all elements of this lazy list followed by the minimal number of occurrences of elem so that the resulting collection has a length of at least len.

    Definition Classes
    LazyListSeqOps
  131. def partition(p: (A) => Boolean): (LazyList[A], LazyList[A])

    A pair of, first, all elements that satisfy predicate p and, second, all elements that do not.

    A pair of, first, all elements that satisfy predicate p and, second, all elements that do not. Interesting because it splits a collection in two.

    The default implementation provided here needs to traverse the collection twice. Strict collections have an overridden version of partition in StrictOptimizedIterableOps, which requires only a single traversal.

    This method preserves laziness; elements are only evaluated individually as needed.

    Definition Classes
    LazyListIterableOps
  132. def partitionMap[A1, A2](f: (A) => Either[A1, A2]): (LazyList[A1], LazyList[A2])

    Applies a function f to each element of the lazy list and returns a pair of lazy lists: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.

    Applies a function f to each element of the lazy list and returns a pair of lazy lists: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.

    Example:

    val xs = `LazyList`(1, "one", 2, "two", 3, "three") partitionMap {
     case i: Int => Left(i)
     case s: String => Right(s)
    }
    // xs == (`LazyList`(1, 2, 3),
    //        `LazyList`(one, two, three))

    This method preserves laziness; elements are only evaluated individually as needed.

    A1

    the element type of the first resulting collection

    A2

    the element type of the second resulting collection

    f

    the 'split function' mapping the elements of this lazy list to an scala.util.Either

    returns

    a pair of lazy lists: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.

    Definition Classes
    LazyListIterableOps
  133. def patch[B >: A](from: Int, other: IterableOnce[B], replaced: Int): LazyList[B]

    Produces a new lazy list where a slice of elements in this lazy list is replaced by another sequence.

    Produces a new lazy list where a slice of elements in this lazy list is replaced by another sequence.

    Patching at negative indices is the same as patching starting at 0. Patching at indices at or larger than the length of the original lazy list appends the patch to the end. If more values are replaced than actually exist, the excess is ignored.

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the element type of the returned lazy list.

    from

    the index of the first replaced element

    other

    the replacement sequence

    replaced

    the number of elements to drop in the original lazy list

    returns

    a new lazy list consisting of all elements of this lazy list except that replaced elements starting from from are replaced by all the elements of other.

    Definition Classes
    LazyListSeqOps
  134. def permutations: Iterator[LazyList[A]]

    Iterates over distinct permutations.

    Iterates over distinct permutations.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    returns

    An Iterator which traverses the distinct permutations of this sequence.

    Definition Classes
    SeqOps
    Example:
    1. "abb".permutations = Iterator(abb, bab, bba)

  135. def prepended[B >: A](elem: B): LazyList[B]

    A copy of the lazy list with an element prepended.

    A copy of the lazy list with an element prepended.

    Also, the original lazy list is not modified, so you will want to capture the result.

    Example:

    scala> val x = List(1)
    x: List[Int] = List(1)
    
    scala> val y = 2 +: x
    y: List[Int] = List(2, 1)
    
    scala> println(x)
    List(1)

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the element type of the returned lazy list.

    elem

    the prepended element

    returns

    a new lazy list consisting of value followed by all elements of this lazy list.

    Definition Classes
    LazyListSeqOps
  136. def prependedAll[B >: A](prefix: IterableOnce[B]): LazyList[B]

    As with :++, returns a new collection containing the elements from the left operand followed by the elements from the right operand.

    As with :++, returns a new collection containing the elements from the left operand followed by the elements from the right operand.

    It differs from :++ in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the element type of the returned collection.

    prefix

    the iterable to prepend.

    returns

    a new lazy list which contains all elements of prefix followed by all the elements of this lazy list.

    Definition Classes
    LazyListSeqOps
  137. def product[B >: A](implicit num: math.Numeric[B]): B

    Multiplies up the elements of this collection.

    Multiplies up the elements of this collection.

    Note: will not terminate for infinite-sized collections.

    B

    the result type of the * operator.

    num

    an implicit parameter defining a set of numeric operations which includes the * operator to be used in forming the product.

    returns

    the product of all elements of this collection with respect to the * operator in num.

    Definition Classes
    IterableOnceOps
  138. def reduce[B >: A](op: (B, B) => B): B

    Reduces the elements of this collection using the specified associative binary operator.

    Reduces the elements of this collection using the specified associative binary operator.

    The order in which operations are performed on elements is unspecified and may be nondeterministic.

    B

    A type parameter for the binary operator, a supertype of A.

    op

    A binary operator that must be associative.

    returns

    The result of applying reduce operator op between all the elements if the collection is nonempty.

    Definition Classes
    IterableOnceOps
    Exceptions thrown

    UnsupportedOperationException if this collection is empty.

  139. def reduceLeft[B >: A](f: (B, A) => B): B

    LazyList specialization of reduceLeft which allows GC to collect along the way.

    LazyList specialization of reduceLeft which allows GC to collect along the way.

    B

    The type of value being accumulated.

    f

    The operation to perform on successive elements of the LazyList.

    returns

    The accumulated value from successive applications of f.

    Definition Classes
    LazyListIterableOnceOps
  140. def reduceLeftOption[B >: A](op: (B, A) => B): Option[B]

    Optionally applies a binary operator to all elements of this collection, going left to right.

    Optionally applies a binary operator to all elements of this collection, going left to right.

    Note: will not terminate for infinite-sized collections.

    Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

    B

    the result type of the binary operator.

    op

    the binary operator.

    returns

    an option value containing the result of reduceLeft(op) if this collection is nonempty, None otherwise.

    Definition Classes
    IterableOnceOps
  141. def reduceOption[B >: A](op: (B, B) => B): Option[B]

    Reduces the elements of this collection, if any, using the specified associative binary operator.

    Reduces the elements of this collection, if any, using the specified associative binary operator.

    The order in which operations are performed on elements is unspecified and may be nondeterministic.

    B

    A type parameter for the binary operator, a supertype of A.

    op

    A binary operator that must be associative.

    returns

    An option value containing result of applying reduce operator op between all the elements if the collection is nonempty, and None otherwise.

    Definition Classes
    IterableOnceOps
  142. def reduceRight[B >: A](op: (A, B) => B): B

    Applies a binary operator to all elements of this collection, going right to left.

    Applies a binary operator to all elements of this collection, going right to left.

    Note: will not terminate for infinite-sized collections.

    Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

    B

    the result type of the binary operator.

    op

    the binary operator.

    returns

    the result of inserting op between consecutive elements of this collection, going right to left:

    op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))

    where x1, ..., xn are the elements of this collection.

    Definition Classes
    IterableOnceOps
    Exceptions thrown

    UnsupportedOperationException if this collection is empty.

  143. def reduceRightOption[B >: A](op: (A, B) => B): Option[B]

    Optionally applies a binary operator to all elements of this collection, going right to left.

    Optionally applies a binary operator to all elements of this collection, going right to left.

    Note: will not terminate for infinite-sized collections.

    Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.

    B

    the result type of the binary operator.

    op

    the binary operator.

    returns

    an option value containing the result of reduceRight(op) if this collection is nonempty, None otherwise.

    Definition Classes
    IterableOnceOps
  144. def reverse: LazyList[A]

    Returns new lazy list with elements in reversed order.

    Returns new lazy list with elements in reversed order.

    Note: will not terminate for infinite-sized collections.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    This method evaluates all elements of the collection.

    returns

    A new lazy list with all elements of this lazy list in reversed order.

    Definition Classes
    LazyListSeqOps
  145. def reverseIterator: Iterator[A]

    An iterator yielding elements in reversed order.

    An iterator yielding elements in reversed order.

    Note: will not terminate for infinite-sized collections.

    Note: xs.reverseIterator is the same as xs.reverse.iterator but might be more efficient.

    returns

    an iterator yielding the elements of this sequence in reversed order

    Definition Classes
    SeqOps
  146. def reversed: collection.Iterable[A]
    Attributes
    protected
    Definition Classes
    IterableOnceOps
  147. def runWith[U](action: (A) => U): (Int) => Boolean

    Composes this partial function with an action function which gets applied to results of this partial function.

    Composes this partial function with an action function which gets applied to results of this partial function. The action function is invoked only for its side effects; its result is ignored.

    Note that expression pf.runWith(action)(x) is equivalent to

    if(pf isDefinedAt x) { action(pf(x)); true } else false

    except that runWith is implemented via applyOrElse and thus potentially more efficient. Using runWith avoids double evaluation of pattern matchers and guards for partial function literals.

    action

    the action function

    returns

    a function which maps arguments x to isDefinedAt(x). The resulting function runs action(this(x)) where this is defined.

    Definition Classes
    PartialFunction
    See also

    applyOrElse.

  148. def sameElements[B >: A](that: IterableOnce[B]): Boolean

    Are the elements of this collection the same (and in the same order) as those of that?

    Are the elements of this collection the same (and in the same order) as those of that?

    Definition Classes
    LinearSeqOpsSeqOps
  149. def scan[B >: A](z: B)(op: (B, B) => B): LazyList[B]

    Computes a prefix scan of the elements of the collection.

    Computes a prefix scan of the elements of the collection.

    Note: The neutral element z may be applied more than once.

    B

    element type of the resulting collection

    z

    neutral element for the operator op

    op

    the associative operator for the scan

    returns

    a new iterable collection containing the prefix scan of the elements in this iterable collection

    Definition Classes
    IterableOps
  150. def scanLeft[B](z: B)(op: (B, A) => B): LazyList[B]

    Produces a lazy list containing cumulative results of applying the operator going left to right, including the initial value.

    Produces a lazy list containing cumulative results of applying the operator going left to right, including the initial value.

    Note: will not terminate for infinite-sized collections.

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the type of the elements in the resulting collection

    z

    the initial value

    op

    the binary operator applied to the intermediate result and the element

    returns

    collection with intermediate results

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  151. def scanRight[B](z: B)(op: (A, B) => B): LazyList[B]

    Produces a collection containing cumulative results of applying the operator going right to left.

    Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result.

    Note: will not terminate for infinite-sized collections.

    Note: might return different results for different runs, unless the underlying collection type is ordered.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    Example:

    List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
    B

    the type of the elements in the resulting collection

    z

    the initial value

    op

    the binary operator applied to the intermediate result and the element

    returns

    collection with intermediate results

    Definition Classes
    IterableOps
  152. def search[B >: A](elem: B, from: Int, to: Int)(implicit ord: Ordering[B]): SearchResult

    Search within an interval in this sorted sequence for a specific element.

    Search within an interval in this sorted sequence for a specific element. If this sequence is an IndexedSeq, a binary search is used. Otherwise, a linear search is used.

    The sequence should be sorted with the same Ordering before calling; otherwise, the results are undefined.

    elem

    the element to find.

    from

    the index where the search starts.

    to

    the index following where the search ends.

    ord

    the ordering to be used to compare elements.

    returns

    a Found value containing the index corresponding to the element in the sequence, or the InsertionPoint where the element would be inserted if the element is not in the sequence.

    Definition Classes
    SeqOps
    Note

    if to <= from, the search space is empty, and an InsertionPoint at from is returned

    See also

    scala.collection.IndexedSeq

    scala.math.Ordering

    scala.collection.SeqOps, method sorted

  153. def search[B >: A](elem: B)(implicit ord: Ordering[B]): SearchResult

    Search this sorted sequence for a specific element.

    Search this sorted sequence for a specific element. If the sequence is an IndexedSeq, a binary search is used. Otherwise, a linear search is used.

    The sequence should be sorted with the same Ordering before calling; otherwise, the results are undefined.

    elem

    the element to find.

    ord

    the ordering to be used to compare elements.

    returns

    a Found value containing the index corresponding to the element in the sequence, or the InsertionPoint where the element would be inserted if the element is not in the sequence.

    Definition Classes
    SeqOps
    See also

    scala.collection.IndexedSeq

    scala.math.Ordering

    scala.collection.SeqOps, method sorted

  154. def segmentLength(p: (A) => Boolean, from: Int): Int

    Computes the length of the longest segment that starts from some index and whose elements all satisfy some predicate.

    Computes the length of the longest segment that starts from some index and whose elements all satisfy some predicate.

    Note: may not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    from

    the index where the search starts.

    returns

    the length of the longest segment of this sequence starting from index from such that every element of the segment satisfies the predicate p.

    Definition Classes
    LinearSeqOpsSeqOps
  155. final def segmentLength(p: (A) => Boolean): Int

    Computes the length of the longest segment that starts from the first element and whose elements all satisfy some predicate.

    Computes the length of the longest segment that starts from the first element and whose elements all satisfy some predicate.

    Note: may not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    the length of the longest segment of this sequence that starts from the first element such that every element of the segment satisfies the predicate p.

    Definition Classes
    SeqOps
  156. final def size: Int

    The size of this sequence.

    The size of this sequence.

    Note: will not terminate for infinite-sized collections.

    returns

    the number of elements in this sequence.

    Definition Classes
    SeqOpsIterableOnceOps
  157. final def sizeCompare(that: collection.Iterable[_]): Int

    Compares the size of this sequence to the size of another Iterable.

    Compares the size of this sequence to the size of another Iterable.

    that

    the Iterable whose size is compared with this sequence's size.

    returns

    A value x where

    x <  0       if this.size <  that.size
    x == 0       if this.size == that.size
    x >  0       if this.size >  that.size

    The method as implemented here does not call size directly; its running time is O(this.size min that.size) instead of O(this.size + that.size). The method should be overridden if computing size is cheap and knownSize returns -1.

    Definition Classes
    SeqOpsIterableOps
  158. final def sizeCompare(otherSize: Int): Int

    Compares the size of this sequence to a test value.

    Compares the size of this sequence to a test value.

    otherSize

    the test value that gets compared with the size.

    returns

    A value x where

    x <  0       if this.size <  otherSize
    x == 0       if this.size == otherSize
    x >  0       if this.size >  otherSize

    The method as implemented here does not call size directly; its running time is O(size min otherSize) instead of O(size). The method should be overridden if computing size is cheap and knownSize returns -1.

    Definition Classes
    SeqOpsIterableOps
    See also

    sizeIs

  159. final def sizeIs: SizeCompareOps

    Returns a value class containing operations for comparing the size of this iterable collection to a test value.

    Returns a value class containing operations for comparing the size of this iterable collection to a test value.

    These operations are implemented in terms of sizeCompare(Int), and allow the following more readable usages:

    this.sizeIs < size     // this.sizeCompare(size) < 0
    this.sizeIs <= size    // this.sizeCompare(size) <= 0
    this.sizeIs == size    // this.sizeCompare(size) == 0
    this.sizeIs != size    // this.sizeCompare(size) != 0
    this.sizeIs >= size    // this.sizeCompare(size) >= 0
    this.sizeIs > size     // this.sizeCompare(size) > 0
    Definition Classes
    IterableOps
    Annotations
    @inline()
  160. def slice(from: Int, until: Int): LazyList[A]

    Selects an interval of elements.

    Selects an interval of elements. The returned lazy list is made up of all elements x which satisfy the invariant:

    from <= indexOf(x) < until

    This method does not evaluate anything until an operation is performed on the result (e.g. calling head or tail, or checking if it is empty). Additionally, it preserves laziness for all but the first from elements.

    from

    the lowest index to include from this lazy list.

    until

    the lowest index to EXCLUDE from this lazy list.

    returns

    a lazy list containing the elements greater than or equal to index from extending up to (but not including) index until of this lazy list.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  161. def sliding(size: Int, step: Int): Iterator[LazyList[A]]

    Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)

    Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)

    The returned iterator will be empty when called on an empty collection. The last element the iterator produces may be smaller than the window size when the original collection isn't exhausted by the window before it and its last element isn't skipped by the step before it.

    The iterator returned by this method mostly preserves laziness; size - step max 1 elements ahead of the iterator are evaluated.

    size

    the number of elements per group

    step

    the distance between the first elements of successive groups

    returns

    An iterator producing lazy lists of size size, except the last element (which may be the only element) will be smaller if there are fewer than size elements remaining to be grouped.

    Definition Classes
    LazyListIterableOps
  162. def sliding(size: Int): Iterator[LazyList[A]]

    Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)

    Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)

    An empty collection returns an empty iterator, and a non-empty collection containing fewer elements than the window size returns an iterator that will produce the original collection as its only element.

    size

    the number of elements per group

    returns

    An iterator producing iterable collections of size size, except for a non-empty collection with less than size elements, which returns an iterator that produces the source collection itself as its only element.

    Definition Classes
    IterableOps
    Examples:
    1. List().sliding(2) = empty iterator

    2. ,
    3. List(1).sliding(2) = Iterator(List(1))

    4. ,
    5. List(1, 2).sliding(2) = Iterator(List(1, 2))

    6. ,
    7. List(1, 2, 3).sliding(2) = Iterator(List(1, 2), List(2, 3))

    See also

    scala.collection.Iterator, method sliding

  163. def sortBy[B](f: (A) => B)(implicit ord: Ordering[B]): LazyList[A]

    Sorts this sequence according to the Ordering which results from transforming an implicitly given Ordering with a transformation function.

    Sorts this sequence according to the Ordering which results from transforming an implicitly given Ordering with a transformation function.

    Note: will not terminate for infinite-sized collections.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    The sort is stable. That is, elements that are equal (as determined by ord.compare) appear in the same order in the sorted sequence as in the original.

    B

    the target type of the transformation f, and the type where the ordering ord is defined.

    f

    the transformation function mapping elements to some other domain B.

    ord

    the ordering assumed on domain B.

    returns

    a sequence consisting of the elements of this sequence sorted according to the ordering where x < y if ord.lt(f(x), f(y)).

    Definition Classes
    SeqOps
    Example:
    1. val words = "The quick brown fox jumped over the lazy dog".split(' ')
      // this works because scala.Ordering will implicitly provide an Ordering[Tuple2[Int, Char]]
      words.sortBy(x => (x.length, x.head))
      res0: Array[String] = Array(The, dog, fox, the, lazy, over, brown, quick, jumped)
    See also

    scala.math.Ordering

  164. def sortWith(lt: (A, A) => Boolean): LazyList[A]

    Sorts this sequence according to a comparison function.

    Sorts this sequence according to a comparison function.

    Note: will not terminate for infinite-sized collections.

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    The sort is stable. That is, elements that are equal (as determined by lt) appear in the same order in the sorted sequence as in the original.

    lt

    the comparison function which tests whether its first argument precedes its second argument in the desired ordering.

    returns

    a sequence consisting of the elements of this sequence sorted according to the comparison function lt.

    Definition Classes
    SeqOps
    Example:
    1. List("Steve", "Tom", "John", "Bob").sortWith(_.compareTo(_) < 0) =
      List("Bob", "John", "Steve", "Tom")
  165. def sorted[B >: A](implicit ord: Ordering[B]): LazyList[A]

    Sorts this sequence according to an Ordering.

    Sorts this sequence according to an Ordering.

    The sort is stable. That is, elements that are equal (as determined by ord.compare) appear in the same order in the sorted sequence as in the original.

    ord

    the ordering to be used to compare elements.

    returns

    a sequence consisting of the elements of this sequence sorted according to the ordering ord.

    Definition Classes
    SeqOps
    See also

    scala.math.Ordering Note: Even when applied to a view or a lazy collection it will always force the elements.

  166. def span(p: (A) => Boolean): (LazyList[A], LazyList[A])

    Splits this iterable collection into a prefix/suffix pair according to a predicate.

    Splits this iterable collection into a prefix/suffix pair according to a predicate.

    Note: c span p is equivalent to (but possibly more efficient than) (c takeWhile p, c dropWhile p), provided the evaluation of the predicate p does not cause any side-effects.

    Note: might return different results for different runs, unless the underlying collection type is ordered.

    p

    the test predicate

    returns

    a pair consisting of the longest prefix of this iterable collection whose elements all satisfy p, and the rest of this iterable collection.

    Definition Classes
    IterableOpsIterableOnceOps
  167. def splitAt(n: Int): (LazyList[A], LazyList[A])

    Splits this iterable collection into a prefix/suffix pair at a given position.

    Splits this iterable collection into a prefix/suffix pair at a given position.

    Note: c splitAt n is equivalent to (but possibly more efficient than) (c take n, c drop n).

    Note: might return different results for different runs, unless the underlying collection type is ordered.

    n

    the position at which to split.

    returns

    a pair of iterable collections consisting of the first n elements of this iterable collection, and the other elements.

    Definition Classes
    IterableOpsIterableOnceOps
  168. def startsWith[B >: A](that: IterableOnce[B], offset: Int = 0): Boolean

    Tests whether this sequence contains the given sequence at a given index.

    Tests whether this sequence contains the given sequence at a given index.

    Note: If the both the receiver object this and the argument that are infinite sequences this method may not terminate.

    that

    the sequence to test

    offset

    the index where the sequence is searched.

    returns

    true if the sequence that is contained in this sequence at index offset, otherwise false.

    Definition Classes
    SeqOps
  169. def stepper[S <: Stepper[_]](implicit shape: StepperShape[A, S]): S

    Returns a scala.collection.Stepper for the elements of this collection.

    Returns a scala.collection.Stepper for the elements of this collection.

    The Stepper enables creating a Java stream to operate on the collection, see scala.jdk.StreamConverters. For collections holding primitive values, the Stepper can be used as an iterator which doesn't box the elements.

    The implicit scala.collection.StepperShape parameter defines the resulting Stepper type according to the element type of this collection.

    Note that this method is overridden in subclasses and the return type is refined to S with EfficientSplit, for example scala.collection.IndexedSeqOps.stepper. For Steppers marked with scala.collection.Stepper.EfficientSplit, the converters in scala.jdk.StreamConverters allow creating parallel streams, whereas bare Steppers can be converted only to sequential streams.

    Definition Classes
    IterableOnce
  170. def stringPrefix: String
    Attributes
    protected[this]
    Definition Classes
    LinearSeqSeqIterable
  171. def sum[B >: A](implicit num: math.Numeric[B]): B

    Sums up the elements of this collection.

    Sums up the elements of this collection.

    Note: will not terminate for infinite-sized collections.

    B

    the result type of the + operator.

    num

    an implicit parameter defining a set of numeric operations which includes the + operator to be used in forming the sum.

    returns

    the sum of all elements of this collection with respect to the + operator in num.

    Definition Classes
    IterableOnceOps
  172. final def synchronized[T0](arg0: => T0): T0

    Executes the code in body with an exclusive lock on this.

    Executes the code in body with an exclusive lock on this.

    returns

    the result of body

    Definition Classes
    AnyRef
  173. def tail: LazyList[A]

    The rest of the collection without its first element.

    The rest of the collection without its first element.

    Definition Classes
    LazyListLinearSeqOpsIterableOps
  174. def tails: Iterator[LazyList[A]]

    Iterates over the tails of this sequence.

    Iterates over the tails of this sequence. The first value will be this sequence and the final one will be an empty sequence, with the intervening values the results of successive applications of tail.

    returns

    an iterator over all the tails of this sequence

    Definition Classes
    LinearSeqOpsIterableOps
    Example:
    1. List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)

  175. def take(n: Int): LazyList[A]

    Selects the first n elements.

    Selects the first n elements.

    This method preserves laziness; elements are only evaluated individually as needed.

    n

    the number of elements to take from this lazy list.

    returns

    a lazy list consisting only of the first n elements of this lazy list, or else the whole lazy list, if it has less than n elements. If n is negative, returns an empty lazy list.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  176. def takeRight(n: Int): LazyList[A]

    Selects the last n elements.

    Selects the last n elements.

    This method does not evaluate anything until an operation is performed on the result (e.g. calling head or tail, or checking if it is empty).

    n

    the number of elements to take from this lazy list.

    returns

    a lazy list consisting only of the last n elements of this lazy list, or else the whole lazy list, if it has less than n elements. If n is negative, returns an empty lazy list.

    Definition Classes
    LazyListIterableOps
  177. def takeWhile(p: (A) => Boolean): LazyList[A]

    Takes longest prefix of elements that satisfy a predicate.

    Takes longest prefix of elements that satisfy a predicate.

    This method preserves laziness; elements are only evaluated individually as needed.

    p

    The predicate used to test elements.

    returns

    the longest prefix of this lazy list whose elements all satisfy the predicate p.

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  178. def tapEach[U](f: (A) => U): LazyList[A]

    Applies a side-effecting function to each element in this collection.

    Applies a side-effecting function to each element in this collection. Strict collections will apply f to their elements immediately, while lazy collections like Views and LazyLists will only apply f on each element if and when that element is evaluated, and each time that element is evaluated.

    This method preserves laziness; elements are only evaluated individually as needed.

    U

    the return type of f

    f

    a function to apply to each element in this lazy list

    returns

    The same logical collection as this

    Definition Classes
    LazyListIterableOpsIterableOnceOps
  179. def to[C1](factory: Factory[A, C1]): C1

    Given a collection factory factory, convert this collection to the appropriate representation for the current element type A.

    Given a collection factory factory, convert this collection to the appropriate representation for the current element type A. Example uses:

    xs.to(List) xs.to(ArrayBuffer) xs.to(BitSet) // for xs: Iterable[Int]

    Definition Classes
    IterableOnceOps
  180. def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]

    Convert collection to array.

    Convert collection to array.

    Implementation note: DO NOT call Array.from from this method.

    Definition Classes
    IterableOnceOps
  181. final def toBuffer[B >: A]: Buffer[B]
    Definition Classes
    IterableOnceOps
    Annotations
    @inline()
  182. def toIndexedSeq: IndexedSeq[A]
    Definition Classes
    IterableOnceOps
  183. final def toIterable: LazyList.this.type

    returns

    This collection as an Iterable[A]. No new collection will be built if this is already an Iterable[A].

    Definition Classes
    IterableIterableOps
  184. def toList: List[A]
    Definition Classes
    IterableOnceOps
  185. def toMap[K, V](implicit ev: <:<[A, (K, V)]): Map[K, V]
    Definition Classes
    IterableOnceOps
  186. final def toSeq: LazyList.this.type

    returns

    This collection as a Seq[A]. This is equivalent to to(Seq) but might be faster.

    Definition Classes
    SeqIterableOnceOps
  187. def toSet[B >: A]: Set[B]
    Definition Classes
    IterableOnceOps
  188. def toString(): String

    This method preserves laziness; elements are only evaluated individually as needed.

    This method preserves laziness; elements are only evaluated individually as needed.

    returns

    a string representation of this collection. An undefined state is represented with "<not computed>" and cycles are represented with "<cycle>" Examples:

    • "LazyList(4, <not computed>)", a non-empty lazy list ;
    • "LazyList(1, 2, 3, <not computed>)", a lazy list with at least three elements ;
    • "LazyList(1, 2, 3, <cycle>)", an infinite lazy list that contains a cycle at the fourth element.
    Definition Classes
    LazyListSeqFunction1Iterable → AnyRef → Any
  189. def toVector: Vector[A]
    Definition Classes
    IterableOnceOps
  190. def transpose[B](implicit asIterable: (A) => collection.Iterable[B]): LazyList[LazyList[B]]

    Transposes this lazy list of iterable collections into a lazy list of lazy lists.

    Transposes this lazy list of iterable collections into a lazy list of lazy lists.

    The resulting collection's type will be guided by the static type of lazy list. For example:

    val xs = List(
               Set(1, 2, 3),
               Set(4, 5, 6)).transpose
    // xs == List(
    //         List(1, 4),
    //         List(2, 5),
    //         List(3, 6))
    
    val ys = Vector(
               List(1, 2, 3),
               List(4, 5, 6)).transpose
    // ys == Vector(
    //         Vector(1, 4),
    //         Vector(2, 5),
    //         Vector(3, 6))

    Note: Even when applied to a view or a lazy collection it will always force the elements.

    This method evaluates all elements of the collection.

    B

    the type of the elements of each iterable collection.

    asIterable

    an implicit conversion which asserts that the element type of this lazy list is an Iterable.

    returns

    a two-dimensional lazy list of lazy lists which has as nth row the nth column of this lazy list.

    Definition Classes
    LazyListIterableOps
  191. def unapply(a: Int): Option[A]

    Tries to extract a B from an A in a pattern matching expression.

    Tries to extract a B from an A in a pattern matching expression.

    Definition Classes
    PartialFunction
  192. def unlift: PartialFunction[Int, B]

    Converts an optional function to a partial function.

    Converts an optional function to a partial function.

    Implicit
    This member is added by an implicit conversion from LazyList[A] toUnliftOps[Int, B] performed by method UnliftOps in scala.Function1.This conversion will take place only if A is a subclass of Option[B] (A <: Option[B]).
    Definition Classes
    UnliftOps
    Example:
    1. Unlike Function.unlift, this UnliftOps.unlift method can be used in extractors.

      val of: Int => Option[String] = { i =>
        if (i == 2) {
          Some("matched by an optional function")
        } else {
          None
        }
      }
      
      util.Random.nextInt(4) match {
        case of.unlift(m) => // Convert an optional function to a pattern
          println(m)
        case _ =>
          println("Not matched")
      }
  193. def unzip[A1, A2](implicit asPair: (A) => (A1, A2)): (LazyList[A1], LazyList[A2])

    Converts this lazy list of pairs into two collections of the first and second half of each pair.

    Converts this lazy list of pairs into two collections of the first and second half of each pair.

    val xs = `LazyList`(
               (1, "one"),
               (2, "two"),
               (3, "three")).unzip
    // xs == (`LazyList`(1, 2, 3),
    //        `LazyList`(one, two, three))

    This method preserves laziness; elements are only evaluated individually as needed.

    A1

    the type of the first half of the element pairs

    A2

    the type of the second half of the element pairs

    asPair

    an implicit conversion which asserts that the element type of this lazy list is a pair.

    returns

    a pair of lazy lists, containing the first, respectively second half of each element pair of this lazy list.

    Definition Classes
    LazyListIterableOps
  194. def unzip3[A1, A2, A3](implicit asTriple: (A) => (A1, A2, A3)): (LazyList[A1], LazyList[A2], LazyList[A3])

    Converts this lazy list of triples into three collections of the first, second, and third element of each triple.

    Converts this lazy list of triples into three collections of the first, second, and third element of each triple.

    val xs = `LazyList`(
               (1, "one", '1'),
               (2, "two", '2'),
               (3, "three", '3')).unzip3
    // xs == (`LazyList`(1, 2, 3),
    //        `LazyList`(one, two, three),
    //        `LazyList`(1, 2, 3))

    This method preserves laziness; elements are only evaluated individually as needed.

    A1

    the type of the first member of the element triples

    A2

    the type of the second member of the element triples

    A3

    the type of the third member of the element triples

    asTriple

    an implicit conversion which asserts that the element type of this lazy list is a triple.

    returns

    a triple of lazy lists, containing the first, second, respectively third member of each element triple of this lazy list.

    Definition Classes
    LazyListIterableOps
  195. def updated[B >: A](index: Int, elem: B): LazyList[B]

    A copy of this lazy list with one single replaced element.

    A copy of this lazy list with one single replaced element.

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the element type of the returned lazy list.

    index

    the position of the replacement

    elem

    the replacing element

    returns

    a new lazy list which is a copy of this lazy list with the element at position index replaced by elem.

    Definition Classes
    LazyListSeqOps
  196. def view: SeqView[A]

    A view over the elements of this collection.

    A view over the elements of this collection.

    Definition Classes
    SeqOpsIterableOps
  197. final def wait(): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--.

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
    Note

    not specified by SLS as a member of AnyRef

  198. final def wait(arg0: Long, arg1: Int): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-int-

    Definition Classes
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    Note

    not specified by SLS as a member of AnyRef

  199. final def wait(arg0: Long): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  200. def withFilter(p: (A) => Boolean): WithFilter[A, LazyList]

    A collection.WithFilter which allows GC of the head of lazy list during processing.

    A collection.WithFilter which allows GC of the head of lazy list during processing.

    This method is not particularly useful for a lazy list, as filter already preserves laziness.

    The collection.WithFilter returned by this method preserves laziness; elements are only evaluated individually as needed.

    p

    the predicate used to test elements.

    returns

    an object of class WithFilter, which supports map, flatMap, foreach, and withFilter operations. All these operations apply to those elements of this lazy list which satisfy the predicate p.

    Definition Classes
    LazyListIterableOps
  201. def writeReplace(): AnyRef
    Attributes
    protected[this]
  202. def zip[B](that: IterableOnce[B]): LazyList[(A, B)]

    Returns a lazy list formed from this lazy list and another iterable collection by combining corresponding elements in pairs.

    Returns a lazy list formed from this lazy list and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.

    This method preserves laziness; elements are only evaluated individually as needed.

    B

    the type of the second half of the returned pairs

    that

    The iterable providing the second half of each result pair

    returns

    a new lazy list containing pairs consisting of corresponding elements of this lazy list and that. The length of the returned collection is the minimum of the lengths of this lazy list and that.

    Definition Classes
    LazyListIterableOps
  203. def zipAll[A1 >: A, B](that: collection.Iterable[B], thisElem: A1, thatElem: B): LazyList[(A1, B)]

    Returns a lazy list formed from this lazy list and another iterable collection by combining corresponding elements in pairs.

    Returns a lazy list formed from this lazy list and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.

    This method preserves laziness; elements are only evaluated individually as needed.

    that

    the iterable providing the second half of each result pair

    thisElem

    the element to be used to fill up the result if this lazy list is shorter than that.

    thatElem

    the element to be used to fill up the result if that is shorter than this lazy list.

    returns

    a new collection of type That containing pairs consisting of corresponding elements of this lazy list and that. The length of the returned collection is the maximum of the lengths of this lazy list and that. If this lazy list is shorter than that, thisElem values are used to pad the result. If that is shorter than this lazy list, thatElem values are used to pad the result.

    Definition Classes
    LazyListIterableOps
  204. def zipWithIndex: LazyList[(A, Int)]

    Zips this lazy list with its indices.

    Zips this lazy list with its indices.

    This method preserves laziness; elements are only evaluated individually as needed.

    returns

    A new lazy list containing pairs consisting of all elements of this lazy list paired with their index. Indices start at 0.

    Definition Classes
    LazyListIterableOpsIterableOnceOps

Deprecated Value Members

  1. def /:[B](z: B)(op: (B, A) => B): B
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    (Since version 2.13.0) Use .iterator.foldLeft instead

  2. final def /:[B](z: B)(op: (B, A) => B): B
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    @deprecated @inline()
    Deprecated

    (Since version 2.13.0) Use foldLeft instead of /:

  3. def :\[B](z: B)(op: (A, B) => B): B
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  4. final def :\[B](z: B)(op: (A, B) => B): B
    Definition Classes
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    Deprecated

    (Since version 2.13.0) Use foldRight instead of :\

  5. def aggregate[B](z: => B)(seqop: (B, A) => B, combop: (B, B) => B): B
    Definition Classes
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    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) aggregate is not relevant for sequential collections. Use foldLeft(z)(seqop) instead.

  6. def collectFirst[B](f: PartialFunction[A, B]): Option[B]
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  7. def companion: IterableFactory[[_]LazyList[_]]
    Definition Classes
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    Annotations
    @deprecated @deprecatedOverriding(message = "Use iterableFactory instead", since = "2.13.0") @inline()
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    (Since version 2.13.0) Use iterableFactory instead

  8. def copyToBuffer(dest: Buffer[A]): Unit
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    (Since version 2.13.0) Use .iterator.copyToBuffer(...) instead

  9. final def copyToBuffer[B >: A](dest: Buffer[B]): Unit
    Definition Classes
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    @deprecated @inline()
    Deprecated

    (Since version 2.13.0) Use dest ++= coll instead

  10. def count(f: (A) => Boolean): Int
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    (Since version 2.13.0) Use .iterator.count(...) instead

  11. def exists(f: (A) => Boolean): Boolean
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    (Since version 2.13.0) Use .iterator.exists(...) instead

  12. def filter(f: (A) => Boolean): Iterator[A]
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  13. def find(p: (A) => Boolean): Option[A]
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  14. def flatMap[B](f: (A) => IterableOnce[B]): IterableOnce[B]
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  15. def fold[A1 >: A](z: A1)(op: (A1, A1) => A1): A1
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  16. def foldLeft[B](z: B)(op: (B, A) => B): B
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  17. def foldRight[B](z: B)(op: (A, B) => B): B
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  18. def forall(f: (A) => Boolean): Boolean
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  19. def foreach[U](f: (A) => U): Unit
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    Deprecated

    (Since version 2.13.0) Use .iterator.foreach(...) instead

  20. def hasDefiniteSize: Boolean

    Tests whether this lazy list is known to have a finite size.

    Tests whether this lazy list is known to have a finite size. All strict collections are known to have finite size. For a non-strict collection such as Stream, the predicate returns true if all elements have been computed. It returns false if the stream is not yet evaluated to the end. Non-empty Iterators usually return false even if they were created from a collection with a known finite size.

    Note: many collection methods will not work on collections of infinite sizes. The typical failure mode is an infinite loop. These methods always attempt a traversal without checking first that hasDefiniteSize returns true. However, checking hasDefiniteSize can provide an assurance that size is well-defined and non-termination is not a concern.

    This method preserves laziness; elements are only evaluated individually as needed.

    returns

    true if this collection is known to have finite size, false otherwise.

    Definition Classes
    LazyListIterableOnceOps
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Check .knownSize instead of .hasDefiniteSize for more actionable information (see scaladoc for details)

  21. def isEmpty: Boolean
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  22. def map[B](f: (A) => B): IterableOnce[B]
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  23. def max(implicit ord: math.Ordering[A]): A
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  24. def maxBy[B](f: (A) => B)(implicit cmp: math.Ordering[B]): A
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  25. def min(implicit ord: math.Ordering[A]): A
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  26. def minBy[B](f: (A) => B)(implicit cmp: math.Ordering[B]): A
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  27. def mkString: String
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  28. def mkString(sep: String): String
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  29. def mkString(start: String, sep: String, end: String): String
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  30. def nonEmpty: Boolean
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  31. final def prefixLength(p: (A) => Boolean): Int

    Returns the length of the longest prefix whose elements all satisfy some predicate.

    Returns the length of the longest prefix whose elements all satisfy some predicate.

    Note: may not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    the length of the longest prefix of this sequence such that every element of the segment satisfies the predicate p.

    Definition Classes
    SeqOps
    Annotations
    @deprecated @inline()
    Deprecated

    (Since version 2.13.0) Use segmentLength instead of prefixLength

  32. def product(implicit num: math.Numeric[A]): A
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  33. def reduce(f: (A, A) => A): A
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  34. def reduceLeft(f: (A, A) => A): A
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  35. def reduceLeftOption(f: (A, A) => A): Option[A]
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  36. def reduceOption(f: (A, A) => A): Option[A]
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  37. def reduceRight(f: (A, A) => A): A
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  38. def reduceRightOption(f: (A, A) => A): Option[A]
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    Definition Classes
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    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use .iterator.reduceRightOption(...) instead

  39. final def repr: LazyList[A]
    Definition Classes
    IterableOps
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use coll instead of repr in a collection implementation, use the collection value itself from the outside

  40. def reverseMap[B](f: (A) => B): LazyList[B]
    Definition Classes
    SeqOps
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use .reverseIterator.map(f).to(...) instead of .reverseMap(f)

  41. def sameElements[B >: A](that: IterableOnce[B]): Boolean
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    Definition Classes
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    (Since version 2.13.0) Use .iterator.sameElements instead

  42. def seq: LazyList.this.type
    Definition Classes
    Iterable
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Iterable.seq always returns the iterable itself

  43. def size: Int
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    This implicitly inherited member is shadowed by one or more members in this class.
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    (lazyList: IterableOnceExtensionMethods[A]).size
    Definition Classes
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    @deprecated
    Deprecated

    (Since version 2.13.0) Use .iterator.size instead

  44. def sum(implicit num: math.Numeric[A]): A
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    (lazyList: IterableOnceExtensionMethods[A]).sum(num)
    Definition Classes
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    (Since version 2.13.0) Use .iterator.sum instead

  45. def to[C1](factory: Factory[A, C1]): C1
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    (lazyList: IterableOnceExtensionMethods[A]).to(factory)
    Definition Classes
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    @deprecated
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    (Since version 2.13.0) Use .iterator.to(factory) instead

  46. def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    This implicitly inherited member is shadowed by one or more members in this class.
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    Definition Classes
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    @deprecated
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    (Since version 2.13.0) Use .iterator.toArray

  47. def toBuffer[B >: A]: Buffer[B]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    Definition Classes
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    @deprecated
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    (Since version 2.13.0) Use .iterator.to(ArrayBuffer) instead

  48. def toIndexedSeq: collection.IndexedSeq[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    This implicitly inherited member is shadowed by one or more members in this class.
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    Definition Classes
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    (Since version 2.13.0) Use .iterator.toIndexedSeq instead

  49. final def toIterable: collection.Iterable[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    Deprecated

    (Since version 2.13.0) Use .iterator.to(Iterable) instead

  50. def toIterator: Iterator[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    Definition Classes
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    Deprecated

    (Since version 2.13.0) Use .iterator instead

  51. final def toIterator: Iterator[A]
    Definition Classes
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    @deprecated @inline()
    Deprecated

    (Since version 2.13.0) Use .iterator instead of .toIterator

  52. def toList: List[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    (Since version 2.13.0) Use .iterator.to(List) instead

  53. def toMap[K, V](implicit ev: <:<[A, (K, V)]): Map[K, V]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    (Since version 2.13.0) Use .iterator.to(Map) instead

  54. def toSeq: Seq[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    (Since version 2.13.0) Use .iterator.to(Seq) instead

  55. def toSet[B >: A]: Set[B]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    Deprecated

    (Since version 2.13.0) Use .iterator.to(Set) instead

  56. def toStream: Stream[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    Definition Classes
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    Deprecated

    (Since version 2.13.0) Use .iterator.to(LazyList) instead

  57. final def toStream: Stream[A]
    Definition Classes
    IterableOnceOps
    Annotations
    @deprecated @inline()
    Deprecated

    (Since version 2.13.0) Use .to(LazyList) instead of .toStream

  58. final def toTraversable: collection.Traversable[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    @deprecated @inline()
    Deprecated

    (Since version 2.13.0) Use .iterator.to(Iterable) instead

  59. final def toTraversable: collection.Traversable[A]

    Converts this iterable collection to an unspecified Iterable.

    Converts this iterable collection to an unspecified Iterable. Will return the same collection if this instance is already Iterable.

    returns

    An Iterable containing all elements of this iterable collection.

    Definition Classes
    IterableOps
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use toIterable instead

  60. def toVector: Vector[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    Definition Classes
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    @deprecated @inline()
    Deprecated

    (Since version 2.13.0) Use .iterator.to(Vector) instead

  61. final def union[B >: A](that: collection.Seq[B]): LazyList[B]

    Produces a new sequence which contains all elements of this sequence and also all elements of a given sequence.

    Produces a new sequence which contains all elements of this sequence and also all elements of a given sequence. xs union ys is equivalent to xs ++ ys.

    B

    the element type of the returned sequence.

    that

    the sequence to add.

    returns

    a new collection which contains all elements of this sequence followed by all elements of that.

    Definition Classes
    SeqOps
    Annotations
    @deprecated @inline()
    Deprecated

    (Since version 2.13.0) Use concat instead

  62. def view(from: Int, until: Int): View[A]

    A view over a slice of the elements of this collection.

    A view over a slice of the elements of this collection.

    Definition Classes
    IterableOps
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use .view.slice(from, until) instead of .view(from, until)

  63. def withFilter(f: (A) => Boolean): Iterator[A]
    Implicit
    This member is added by an implicit conversion from LazyList[A] toIterableOnceExtensionMethods[A] performed by method iterableOnceExtensionMethods in scala.collection.IterableOnce.
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    This implicitly inherited member is shadowed by one or more members in this class.
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    (lazyList: IterableOnceExtensionMethods[A]).withFilter(f)
    Definition Classes
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    Annotations
    @deprecated
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    (Since version 2.13.0) Use .iterator.withFilter(...) instead

  64. def [B](y: B): (LazyList[A], B)
    Implicit
    This member is added by an implicit conversion from LazyList[A] toArrowAssoc[LazyList[A]] performed by method ArrowAssoc in scala.Predef.This conversion will take place only if A is a subclass of Option[Nothing] (A <: Option[Nothing]).
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use -> instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.

Inherited from java.io.Serializable

Inherited from LinearSeq[A]

Inherited from LinearSeqOps[A, [X]LazyList[X], LazyList[A]]

Inherited from collection.LinearSeq[A]

Inherited from collection.LinearSeqOps[A, [X]LazyList[X], LazyList[A]]

Inherited from AbstractSeq[A]

Inherited from Seq[A]

Inherited from SeqOps[A, [_]LazyList[_], LazyList[A]]

Inherited from Iterable[A]

Inherited from collection.AbstractSeq[A]

Inherited from collection.Seq[A]

Inherited from Equals

Inherited from collection.SeqOps[A, [_]LazyList[_], LazyList[A]]

Inherited from PartialFunction[Int, A]

Inherited from (Int) => A

Inherited from AbstractIterable[A]

Inherited from collection.Iterable[A]

Inherited from IterableFactoryDefaults[A, [x]LazyList[x]]

Inherited from IterableOps[A, [_]LazyList[_], LazyList[A]]

Inherited from IterableOnceOps[A, [_]LazyList[_], LazyList[A]]

Inherited from IterableOnce[A]

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion UnliftOps fromLazyList[A] to UnliftOps[Int, B]

Inherited by implicit conversion iterableOnceExtensionMethods fromLazyList[A] to IterableOnceExtensionMethods[A]

Inherited by implicit conversion toDeferrer fromLazyList[A] to Deferrer[A]

Inherited by implicit conversion any2stringadd fromLazyList[A] to any2stringadd[LazyList[A]]

Inherited by implicit conversion StringFormat fromLazyList[A] to StringFormat[LazyList[A]]

Inherited by implicit conversion Ensuring fromLazyList[A] to Ensuring[LazyList[A]]

Inherited by implicit conversion ArrowAssoc fromLazyList[A] to ArrowAssoc[LazyList[A]]

Ungrouped