# LazyList

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 =>
n._1 + n._2
}
fibs.take(5).foreach(println)
fibs.take(6).foreach(println)
}

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

// And then prints
//
// 0
// 1
// 1
// 2
// 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"``````
Type parameters:
A

the type of the elements contained in this lazy list.

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

Companion:
object
Source:
LazyList.scala
trait LinearSeq[A]
trait LinearSeq[A]
class AbstractSeq[A]
trait Seq[A]
trait SeqOps[A, LazyList, LazyList[A]]
trait Iterable[A]
class AbstractSeq[A]
trait Seq[A]
trait Equals
trait SeqOps[A, LazyList, LazyList[A]]
trait Int => A
trait Iterable[A]
trait IterableOnce[A]
class Object
trait Matchable
class Any

## Value members

### Concrete methods

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.

Source:
LazyList.scala
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.

Source:
LazyList.scala
override def addString(sb: StringBuilder, start: String, sep: String, end: String): 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.

Value parameters:
end

the ending string.

sb

the string builder to which elements are appended.

sep

the separator string.

start

the starting string.

Returns:

the string builder `b` to which elements were appended.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override def diff[B >: A](that: 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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).

Definition Classes
Source:
LazyList.scala
override 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`.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Type parameters:
B

The type of value being accumulated.

Value parameters:
op

The operation to perform on successive elements of the `LazyList`.

z

The initial value seeded into the function `op`.

Returns:

The accumulated value from successive applications of `op`.

Definition Classes
Source:
LazyList.scala
def force: LazyList[A]

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

Source:
LazyList.scala
override 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).

Value parameters:
f

The treatment to apply to each element.

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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
Definition Classes
Source:
LazyList.scala
override def intersect[B >: A](that: 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.

Definition Classes
Source:
LazyList.scala
override def isEmpty
Definition Classes
Source:
LazyList.scala
override def iterableFactory
Definition Classes
Source:
LazyList.scala
override 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
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
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.

Value parameters:
suffix

The collection that gets appended to this lazy list

Returns:

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

Source:
LazyList.scala
override def lazyZip[B](that: Iterable[B]): LazyZip2[A, B, LazyList[A]]

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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Type parameters:
B

The type of value being accumulated.

Value parameters:
f

The operation to perform on successive elements of the `LazyList`.

Returns:

The accumulated value from successive applications of `f`.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override def tail: LazyList[A]
Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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).

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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
Source:
LazyList.scala
override def transpose[B](implicit asIterable: A => 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala
override def zipAll[A1 >: A, B](that: 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.

Definition Classes
Source:
LazyList.scala
override 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.

Definition Classes
Source:
LazyList.scala

### Deprecated methods

@deprecated("Check .knownSize instead of .hasDefiniteSize for more actionable information (see scaladoc for details)", "2.13.0")
override def hasDefiniteSize

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.

Deprecated
Definition Classes
Source:
LazyList.scala

### Inherited methods

final def ++[B >: A](suffix: IterableOnce[B]): LazyList[B]

Alias for `concat`

Alias for `concat`

Inherited from:
IterableOps
Source:
Iterable.scala
final override def ++:[B >: A](prefix: IterableOnce[B]): LazyList[B]

Alias for `prependedAll`

Alias for `prependedAll`

Definition Classes
Inherited from:
SeqOps
Source:
Seq.scala
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.

Inherited from:
SeqOps
Source:
Seq.scala
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.

Inherited from:
SeqOps
Source:
Seq.scala
final def :++[B >: A](suffix: IterableOnce[B]): LazyList[B]

Alias for `appendedAll`

Alias for `appendedAll`

Inherited from:
SeqOps
Source:
Seq.scala

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 =

h: StringBuilder = 1234``````
Value parameters:
b

the string builder to which elements are appended.

Returns:

the string builder `b` to which elements were appended.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala

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 =

res0: StringBuilder = 1, 2, 3, 4``````
Value parameters:
b

the string builder to which elements are appended.

sep

the separator string.

Returns:

the string builder `b` to which elements were appended.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala

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. For efficiency, it is recommended to call applyOrElse instead of isDefinedAt or apply.

Type parameters:
C

the result type of the transformation function.

Value parameters:
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))`.

Inherited from:
PartialFunction
Source:
PartialFunction.scala
override 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).

Type parameters:
C

the result type of the transformation function.

Value parameters:
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
Inherited from:
PartialFunction
Source:
PartialFunction.scala
@throws(scala.throws.\$lessinit\$greater\$default\$1[scala.IndexOutOfBoundsException])
override def apply(n: Int): A
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
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.

Value parameters:
default

the fallback function

x

the function argument

Returns:

the result of this function or fallback function application.

Inherited from:
PartialFunction
Source:
PartialFunction.scala
def canEqual(that: Any): Boolean
Inherited from:
Seq
Source:
Seq.scala

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.

Example:

`"abbbc".combinations(2) = Iterator(ab, ac, bb, bc)`

Inherited from:
SeqOps
Source:
Seq.scala

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. For efficiency, it is recommended to call applyOrElse instead of isDefinedAt or apply.

Type parameters:
R

the parameter type of the transformation function.

Value parameters:
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))`.

Inherited from:
PartialFunction
Source:
PartialFunction.scala
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.

Type parameters:
A

the type to which function `g` can be applied

Value parameters:
g

a function A => T1

Returns:

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

Inherited from:
Function1
Source:
Function1.scala
final override def concat[B >: A](suffix: IterableOnce[B]): LazyList[B]
Definition Classes
Inherited from:
SeqOps
Source:
Seq.scala
override def contains[A1 >: A](elem: A1): Boolean
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
def containsSlice[B >: A](that: 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.

Value parameters:
that

the sequence to test

Returns:

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

Inherited from:
SeqOps
Source:
Seq.scala
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.

Type parameters:
B

the type of the elements of the array.

Value parameters:
len

the maximal number of elements to copy.

start

the starting index of xs.

xs

the array to fill.

Returns:

the number of elements written to the array

Note:

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
@deprecatedOverriding("This should always forward to the 3-arg version of this method", since = "2.13.4")
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.

Type parameters:
B

the type of the elements of the array.

Value parameters:
start

the starting index of xs.

xs

the array to fill.

Returns:

the number of elements written to the array

Note:

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
@deprecatedOverriding("This should always forward to the 3-arg version of this method", since = "2.13.4")
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.

Type parameters:
B

the type of the elements of the array.

Value parameters:
xs

the array to fill.

Returns:

the number of elements written to the array

Note:

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Type parameters:
B

the type of the elements of `that`

Value parameters:
p

the test predicate, which relates elements from both collections

that

the other collection

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`

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def corresponds[B](that: 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.

Type parameters:
B

the type of the elements of `that`

Value parameters:
p

the test predicate, which relates elements from both sequences

that

the other sequence

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`.

Inherited from:
SeqOps
Source:
Seq.scala
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.

Value parameters:
p

the predicate used to test elements.

Returns:

the number of elements satisfying the predicate `p`.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala

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.

Inherited from:
SeqOps
Source:
Seq.scala
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`.

Type parameters:
B

the type of the elements after being transformed by `f`

Value parameters:
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.

Inherited from:
SeqOps
Source:
Seq.scala

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.

Example:

``````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
}``````
Inherited from:
PartialFunction
Source:
PartialFunction.scala
override def empty: LazyList[A]
Definition Classes
Inherited from:
IterableFactoryDefaults
Source:
Iterable.scala
def endsWith[B >: A](that: 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.

Value parameters:
that

the sequence to test

Returns:

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

Inherited from:
SeqOps
Source:
Seq.scala
override def equals(o: Any): Boolean
Definition Classes
Seq -> Equals -> Any
Inherited from:
Seq
Source:
Seq.scala
override def exists(p: A => Boolean): Boolean
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
override def findLast(p: A => Boolean): Option[A]
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
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.

Type parameters:
A1

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

Value parameters:
op

a binary operator that must be associative.

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).

Returns:

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

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Type parameters:
B

the result type of the binary operator.

Value parameters:
op

the binary operator.

z

the start value.

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(x1, op(x2, ... op(xn, z)...))` where `x1, ..., xn` are the elements of this collection. Returns `z` if this collection is empty.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
override def forall(p: A => Boolean): Boolean
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
protected def fromSpecific(coll: IterableOnce[A]): LazyList[A]
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.

Type parameters:
K

the type of keys returned by the discriminator function.

Value parameters:
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`.

Inherited from:
IterableOps
Source:
Iterable.scala
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.

Type parameters:
B

the type of values returned by the transformation function

K

the type of keys returned by the discriminator function

Value parameters:
f

the element transformation function

key

the discriminator function

Inherited from:
IterableOps
Source:
Iterable.scala
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 `f` 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.

Inherited from:
IterableOps
Source:
Iterable.scala
override def hashCode(): Int
Definition Classes
Seq -> Any
Inherited from:
Seq
Source:
Seq.scala
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
@deprecatedOverriding("Override indexOf(elem, from) instead - indexOf(elem) calls indexOf(elem, 0)", "2.13.0")
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.

Type parameters:
B

the type of the element `elem`.

Value parameters:
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.

Inherited from:
SeqOps
Source:
Seq.scala
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.

Type parameters:
B

the type of the element `elem`.

Value parameters:
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.

Inherited from:
SeqOps
Source:
Seq.scala
@deprecatedOverriding("Override indexOfSlice(that, from) instead - indexOfSlice(that) calls indexOfSlice(that, 0)", "2.13.0")
def indexOfSlice[B >: A](that: 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.

Value parameters:
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.

Inherited from:
SeqOps
Source:
Seq.scala
def indexOfSlice[B >: A](that: 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.

Value parameters:
from

the start index

that

the sequence to test

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.

Inherited from:
SeqOps
Source:
Seq.scala
override def indexWhere(p: A => Boolean, from: Int): Int
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
@deprecatedOverriding("Override indexWhere(p, from) instead - indexWhere(p) calls indexWhere(p, 0)", "2.13.0")
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.

Value parameters:
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.

Inherited from:
SeqOps
Source:
Seq.scala

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.

Inherited from:
SeqOps
Source:
Seq.scala
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.

Inherited from:
IterableOps
Source:
Iterable.scala

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

Example:

`List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)`

Inherited from:
IterableOps
Source:
Iterable.scala
override def isDefinedAt(x: Int): Boolean
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
override def isTraversableAgain
Definition Classes
Inherited from:
IterableOps
Source:
Iterable.scala
override def last: A
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
def lastIndexOf[B >: A](elem: B, end: Int): 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.

Type parameters:
B

the type of the element `elem`.

Value parameters:
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.

Inherited from:
SeqOps
Source:
Seq.scala
@deprecatedOverriding("Override lastIndexOfSlice(that, end) instead - lastIndexOfSlice(that) calls lastIndexOfSlice(that, Int.MaxValue)", "2.13.0")
def lastIndexOfSlice[B >: A](that: 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.

Value parameters:
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.

Inherited from:
SeqOps
Source:
Seq.scala
def lastIndexOfSlice[B >: A](that: 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.

Value parameters:
end

the end index

that

the sequence to test

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.

Inherited from:
SeqOps
Source:
Seq.scala
override def lastIndexWhere(p: A => Boolean, end: Int): Int
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
@deprecatedOverriding("Override lastIndexWhere(p, end) instead - lastIndexWhere(p) calls lastIndexWhere(p, Int.MaxValue)", "2.13.0")
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.

Value parameters:
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.

Inherited from:
SeqOps
Source:
Seq.scala

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.

Inherited from:
IterableOps
Source:
Iterable.scala
def length: Int
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
override def lengthCompare(that: Iterable[_]): Int
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
override def lengthCompare(len: Int): Int
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
final def lengthIs

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``````
Inherited from:
SeqOps
Source:
Seq.scala
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.

Function.unlift

Inherited from:
PartialFunction
Source:
PartialFunction.scala
def max[B >: A](implicit ord: Ordering[B]): A

Finds the largest element.

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type parameters:
B

The type over which the ordering is defined.

Value parameters:
ord

An ordering to be used for comparing elements.

Returns:

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

Throws:
UnsupportedOperationException

if this collection is empty.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def maxBy[B](f: A => B)(implicit cmp: 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.

Type parameters:
B

The result type of the function f.

Value parameters:
cmp

An ordering to be used for comparing elements.

f

The measuring function.

Returns:

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

Throws:
UnsupportedOperationException

if this collection is empty.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def maxByOption[B](f: A => B)(implicit cmp: 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.

Type parameters:
B

The result type of the function f.

Value parameters:
cmp

An ordering to be used for comparing elements.

f

The measuring function.

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`.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def maxOption[B >: A](implicit ord: Ordering[B]): Option[A]

Finds the largest element.

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type parameters:
B

The type over which the ordering is defined.

Value parameters:
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`.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def min[B >: A](implicit ord: Ordering[B]): A

Finds the smallest element.

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type parameters:
B

The type over which the ordering is defined.

Value parameters:
ord

An ordering to be used for comparing elements.

Returns:

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

Throws:
UnsupportedOperationException

if this collection is empty.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def minBy[B](f: A => B)(implicit cmp: 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.

Type parameters:
B

The result type of the function f.

Value parameters:
cmp

An ordering to be used for comparing elements.

f

The measuring function.

Returns:

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

Throws:
UnsupportedOperationException

if this collection is empty.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def minByOption[B](f: A => B)(implicit cmp: 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.

Type parameters:
B

The result type of the function f.

Value parameters:
cmp

An ordering to be used for comparing elements.

f

The measuring function.

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`.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def minOption[B >: A](implicit ord: Ordering[B]): Option[A]

Finds the smallest element.

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type parameters:
B

The type over which the ordering is defined.

Value parameters:
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`.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
final def mkString

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.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Value parameters:
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`.

Example:

`List(1, 2, 3).mkString("|") = "1|2|3"`

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Value parameters:
end

the ending string.

sep

the separator string.

start

the starting 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`.

Example:

`List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"`

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
@deprecatedOverriding("nonEmpty is defined as !isEmpty; override isEmpty instead", "2.13.0")

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.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Type parameters:
A1

the argument type of the fallback function

B1

the result type of the fallback function

Value parameters:
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.

Inherited from:
PartialFunction
Source:
PartialFunction.scala

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.

Example:

`"abb".permutations = Iterator(abb, bab, bba)`

Inherited from:
SeqOps
Source:
Seq.scala
def product[B >: A](implicit num: 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.

Type parameters:
B

the result type of the `*` operator.

Value parameters:
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`.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Type parameters:
B

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

Value parameters:
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.

Throws:
UnsupportedOperationException

if this collection is empty.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Type parameters:
B

the result type of the binary operator.

Value parameters:
op

the binary operator.

Returns:

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

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Type parameters:
B

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

Value parameters:
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.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Type parameters:
B

the result type of the binary operator.

Value parameters:
op

the binary operator.

Returns:

the result of inserting `op` between consecutive elements of this collection, going right to left: `op(x1, op(x2, ..., op(xn-1, xn)...))` where `x1, ..., xn` are the elements of this collection.

Throws:
UnsupportedOperationException

if this collection is empty.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Type parameters:
B

the result type of the binary operator.

Value parameters:
op

the binary operator.

Returns:

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

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala

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

Inherited from:
SeqOps
Source:
Seq.scala
protected def reversed: Iterable[A]
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Value parameters:
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.

`applyOrElse`.

Inherited from:
PartialFunction
Source:
PartialFunction.scala
override def sameElements[B >: A](that: IterableOnce[B]): Boolean
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
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.

Type parameters:
B

element type of the resulting collection

Value parameters:
op

the associative operator for the scan

z

neutral element for the operator `op`

Returns:

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

Inherited from:
IterableOps
Source:
Iterable.scala
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)``
Type parameters:
B

the type of the elements in the resulting collection

Value parameters:
op

the binary operator applied to the intermediate result and the element

z

the initial value

Returns:

collection with intermediate results

Inherited from:
IterableOps
Source:
Iterable.scala
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.

Value parameters:
elem

the element to find.

from

the index where the search starts.

ord

the ordering to be used to compare elements.

to

the index following where the search ends.

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.

Note:

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

Inherited from:
SeqOps
Source:
Seq.scala
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.

Value parameters:
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.

Inherited from:
SeqOps
Source:
Seq.scala
override def segmentLength(p: A => Boolean, from: Int): Int
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
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.

Value parameters:
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`.

Inherited from:
SeqOps
Source:
Seq.scala
final override def size: Int
Definition Classes
Inherited from:
SeqOps
Source:
Seq.scala
final override def sizeCompare(that: Iterable[_]): Int
Definition Classes
Inherited from:
SeqOps
Source:
Seq.scala
final override def sizeCompare(otherSize: Int): Int
Definition Classes
Inherited from:
SeqOps
Source:
Seq.scala
final def sizeIs

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``````
Inherited from:
IterableOps
Source:
Iterable.scala
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.

Value parameters:
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.

scala.collection.Iterator, method `sliding`

Example:

`List().sliding(2) = empty iterator`

`List(1).sliding(2) = Iterator(List(1))`

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

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

Inherited from:
IterableOps
Source:
Iterable.scala
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.

Type parameters:
B

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

Value parameters:
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))`.

Example:

``````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]]
res0: Array[String] = Array(The, dog, fox, the, lazy, over, brown, quick, jumped)``````
Inherited from:
SeqOps
Source:
Seq.scala
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.

Value parameters:
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`.

Example:

``````List("Steve", "Tom", "John", "Bob").sortWith(_.compareTo(_) < 0) =
List("Bob", "John", "Steve", "Tom")``````
Inherited from:
SeqOps
Source:
Seq.scala
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.

Value parameters:
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`.

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

Inherited from:
SeqOps
Source:
Seq.scala
def span(p: A => Boolean): (LazyList[A], LazyList[A])
Inherited from:
IterableOps
Source:
Iterable.scala
override def splitAt(n: Int): (LazyList[A], LazyList[A])
Definition Classes
Inherited from:
IterableOps
Source:
Iterable.scala
def startsWith[B >: A](that: IterableOnce[B], offset: Int): 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.

Value parameters:
offset

the index where the sequence is searched.

that

the sequence to test

Returns:

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

Inherited from:
SeqOps
Source:
Seq.scala
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.

Inherited from:
IterableOnce
Source:
IterableOnce.scala
def sum[B >: A](implicit num: 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.

Type parameters:
B

the result type of the `+` operator.

Value parameters:
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`.

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
override def tails: Iterator[LazyList[A]]
Definition Classes
Inherited from:
LinearSeqOps
Source:
LinearSeq.scala
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]

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def toArray[B >: A : ClassTag]: Array[B]

Convert collection to array.

Convert collection to array.

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

Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
final def toBuffer[B >: A]: Buffer[B]
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def toList: List[A]
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
def toMap[K, V](implicit ev: A <:< (K, V)): Map[K, V]
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
final override def toSeq: LazyList[A]
Definition Classes
Inherited from:
Seq
Source:
Seq.scala
def toSet[B >: A]: Set[B]
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
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.

Inherited from:
PartialFunction
Source:
PartialFunction.scala
override def view: SeqView[A]
Definition Classes
Inherited from:
SeqOps
Source:
Seq.scala

### Deprecated and Inherited methods

@deprecated("Use foldLeft instead of /:", "2.13.0") @inline
final def /:[B](z: B)(op: (B, A) => B): B
Deprecated
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
@deprecated("Use foldRight instead of :\\", "2.13.0") @inline
final def :\[B](z: B)(op: (A, B) => B): B
Deprecated
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
@deprecated("`aggregate` is not relevant for sequential collections. Use `foldLeft(z)(seqop)` instead.", "2.13.0")
def aggregate[B](z: => B)(seqop: (B, A) => B, combop: (B, B) => B): B
Deprecated
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
Deprecated
Inherited from:
IterableOps
Source:
Iterable.scala
@deprecated("Use `dest ++= coll` instead", "2.13.0") @inline
final def copyToBuffer[B >: A](dest: Buffer[B]): Unit
Deprecated
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
@deprecated("Use segmentLength instead of prefixLength", "2.13.0") @inline
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.

Value parameters:
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`.

Deprecated
Inherited from:
SeqOps
Source:
Seq.scala
@deprecated("Use coll instead of repr in a collection implementation, use the collection value itself from the outside", "2.13.0")
final def repr: LazyList[A]
Deprecated
Inherited from:
IterableOps
Source:
Iterable.scala
@deprecated("Use .reverseIterator.map(f).to(...) instead of .reverseMap(f)", "2.13.0")
def reverseMap[B](f: A => B): LazyList[B]
Deprecated
Inherited from:
SeqOps
Source:
Seq.scala
@deprecated("Iterable.seq always returns the iterable itself", "2.13.0")
def seq: LazyList[A]
Deprecated
Inherited from:
Iterable
Source:
Iterable.scala
@deprecated("toIterable is internal and will be made protected; its name is similar to `toList` or `toSeq`, but it doesn\'t copy non-immutable collections", "2.13.7")
final def toIterable: LazyList[A]
Deprecated
Inherited from:
Iterable
Source:
Iterable.scala
@deprecated("Use .iterator instead of .toIterator", "2.13.0") @inline
final def toIterator: Iterator[A]
Deprecated
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
@deprecated("Use .to(LazyList) instead of .toStream", "2.13.0") @inline
final def toStream: Stream[A]
Deprecated
Inherited from:
IterableOnceOps
Source:
IterableOnce.scala
@deprecated("toTraversable is internal and will be made protected; its name is similar to `toList` or `toSeq`, but it doesn\'t copy non-immutable collections", "2.13.0")
final def toTraversable: Iterable[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.

Deprecated
Inherited from:
IterableOps
Source:
Iterable.scala
final def union[B >: A](that: 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`.

Type parameters:
B

the element type of the returned sequence.

Value parameters:
that

Returns:

a new collection which contains all elements of this sequence followed by all elements of `that`.

Deprecated
Inherited from:
SeqOps
Source:
Seq.scala
@deprecated("Use .view.slice(from, until) instead of .view(from, until)", "2.13.0")
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.

Deprecated
Inherited from:
IterableOps
Source:
Iterable.scala