trait IterableOnceOps[+A, +CC[_], +C] extends Any
This implementation trait can be mixed into an IterableOnce
to get the basic methods that are shared between
Iterator
and Iterable
. The IterableOnce
must support multiple calls to iterator
but may or may not
return the same Iterator
every time.
- Self Type
- IterableOnceOps[A, CC, C] with IterableOnce[A]
- Source
- IterableOnce.scala
- Alphabetic
- By Inheritance
- IterableOnceOps
- Any
- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
- Hide All
- Show All
- Public
- Protected
Abstract Value Members
- abstract def collect[B](pf: PartialFunction[A, B]): CC[B]
Builds a new collection by applying a partial function to all elements of this collection on which the function is defined.
Builds a new collection by applying a partial function to all elements of this collection on which the function is defined.
- B
the element type of the returned collection.
- pf
the partial function which filters and maps the collection.
- returns
a new collection resulting from applying the given partial function
pf
to each element on which it is defined and collecting the results. The order of the elements is preserved.
- abstract def drop(n: Int): C
Selects all elements except the first
n
ones.Selects all elements except the first
n
ones.Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
the number of elements to drop from this collection.
- returns
a collection consisting of all elements of this collection except the first
n
ones, or else the empty collection, if this collection has less thann
elements. Ifn
is negative, don't drop any elements.
- abstract def dropWhile(p: (A) => Boolean): C
Selects all elements except the longest prefix that satisfies a predicate.
Selects all elements except the longest prefix that satisfies a predicate.
The matching prefix starts with the first element of this collection, and the element following the prefix is the first element that does not satisfy the predicate. The matching prefix may be empty, so that this method returns the entire collection.
Example:
scala> List(1, 2, 3, 100, 4).dropWhile(n => n < 10) val res0: List[Int] = List(100, 4) scala> List(1, 2, 3, 100, 4).dropWhile(n => n == 0) val res1: List[Int] = List(1, 2, 3, 100, 4)
Use span to obtain both the prefix and suffix. Use filterNot to drop all elements that satisfy the predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- p
The predicate used to test elements.
- returns
the longest suffix of this collection whose first element does not satisfy the predicate
p
.
- abstract def filter(p: (A) => Boolean): C
Selects all elements of this collection which satisfy a predicate.
Selects all elements of this collection which satisfy a predicate.
- p
the predicate used to test elements.
- returns
a new collection consisting of all elements of this collection that satisfy the given predicate
p
. The order of the elements is preserved.
- abstract def filterNot(pred: (A) => Boolean): C
Selects all elements of this collection which do not satisfy a predicate.
Selects all elements of this collection which do not satisfy a predicate.
- pred
the predicate used to test elements.
- returns
a new collection consisting of all elements of this collection that do not satisfy the given predicate
pred
. Their order may not be preserved.
- abstract def flatMap[B](f: (A) => IterableOnce[B]): CC[B]
Builds a new collection by applying a function to all elements of this collection and using the elements of the resulting collections.
Builds a new collection by applying a function to all elements of this collection 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 collection. 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)
- B
the element type of the returned collection.
- f
the function to apply to each element.
- returns
a new collection resulting from applying the given collection-valued function
f
to each element of this collection and concatenating the results.
- abstract def flatten[B](implicit asIterable: (A) => IterableOnce[B]): CC[B]
Converts this collection of iterable collections into a collection formed by the elements of these iterable collections.
Converts this collection of iterable collections into a collection formed by the elements of these iterable collections.
The resulting collection's type will be guided by the type of collection. 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)
- B
the type of the elements of each iterable collection.
- asIterable
an implicit conversion which asserts that the element type of this collection is an
Iterable
.- returns
a new collection resulting from concatenating all element collections.
- abstract def getClass(): Class[_ <: AnyRef]
Returns the runtime class representation of the object.
Returns the runtime class representation of the object.
- returns
a class object corresponding to the runtime type of the receiver.
- Definition Classes
- Any
- abstract def map[B](f: (A) => B): CC[B]
Builds a new collection by applying a function to all elements of this collection.
Builds a new collection by applying a function to all elements of this collection.
- B
the element type of the returned collection.
- f
the function to apply to each element.
- returns
a new collection resulting from applying the given function
f
to each element of this collection and collecting the results.
- abstract def scanLeft[B](z: B)(op: (B, A) => B): CC[B]
Produces a collection containing cumulative results of applying the operator going left to right, including the initial value.
Produces a collection containing cumulative results of applying the operator going left to right, including the initial value.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- B
the type of the elements in the resulting collection
- z
the initial value
- op
the binary operator applied to the intermediate result and the element
- returns
collection with intermediate results
- abstract def slice(from: Int, until: Int): C
Selects an interval of elements.
Selects an interval of elements. The returned collection is made up of all elements
x
which satisfy the invariant:from <= indexOf(x) < until
Note: might return different results for different runs, unless the underlying collection type is ordered.
- from
the lowest index to include from this collection.
- until
the lowest index to EXCLUDE from this collection.
- returns
a collection containing the elements greater than or equal to index
from
extending up to (but not including) indexuntil
of this collection.
- abstract def span(p: (A) => Boolean): (C, C)
Splits this collection into a prefix/suffix pair according to a predicate.
Splits this collection into a prefix/suffix pair according to a predicate.
Note:
c span p
is equivalent to (but possibly more efficient than)(c takeWhile p, c dropWhile p)
, provided the evaluation of the predicatep
does not cause any side-effects.Note: might return different results for different runs, unless the underlying collection type is ordered.
- p
the test predicate
- returns
a pair consisting of the longest prefix of this collection whose elements all satisfy
p
, and the rest of this collection.
- abstract def take(n: Int): C
Selects the first
n
elements.Selects the first
n
elements.Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
the number of elements to take from this collection.
- returns
a collection consisting only of the first
n
elements of this collection, or else the whole collection, if it has less thann
elements. Ifn
is negative, returns an empty collection.
- abstract def takeWhile(p: (A) => Boolean): C
Selects the longest prefix of elements that satisfy a predicate.
Selects the longest prefix of elements that satisfy a predicate.
The matching prefix starts with the first element of this collection, and the element following the prefix is the first element that does not satisfy the predicate. The matching prefix may empty, so that this method returns an empty collection.
Example:
scala> List(1, 2, 3, 100, 4).takeWhile(n => n < 10) val res0: List[Int] = List(1, 2, 3) scala> List(1, 2, 3, 100, 4).takeWhile(n => n == 0) val res1: List[Int] = List()
Use span to obtain both the prefix and suffix. Use filter to retain only those elements from the entire collection that satisfy the predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- p
The predicate used to test elements.
- returns
the longest prefix of this collection whose elements all satisfy the predicate
p
.
- abstract def tapEach[U](f: (A) => U): C
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 applyf
on each element if and when that element is evaluated, and each time that element is evaluated.- U
the return type of f
- f
a function to apply to each element in this collection
- returns
The same logical collection as this
- abstract def zipWithIndex: CC[(A, Int)]
Zips this collection with its indices.
Zips this collection with its indices.
- returns
A new collection containing pairs consisting of all elements of this collection paired with their index. Indices start at
0
.
List("a", "b", "c").zipWithIndex == List(("a", 0), ("b", 1), ("c", 2))
Example:
Concrete Value Members
- final def !=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
- returns
true
if !(this == that), false otherwise.
- Definition Classes
- Any
- final def ##: Int
Equivalent to
x.hashCode
except for boxed numeric types andnull
.Equivalent to
x.hashCode
except for boxed numeric types andnull
. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. Fornull
returns a hashcode wherenull.hashCode
throws aNullPointerException
.- returns
a hash value consistent with ==
- Definition Classes
- Any
- def +(other: String): String
- Implicit
- This member is added by an implicit conversion from IterableOnceOps[A, CC, C] toany2stringadd[IterableOnceOps[A, CC, C]] performed by method any2stringadd in scala.Predef.
- Definition Classes
- any2stringadd
- def ->[B](y: B): (IterableOnceOps[A, CC, C], B)
- Implicit
- This member is added by an implicit conversion from IterableOnceOps[A, CC, C] toArrowAssoc[IterableOnceOps[A, CC, C]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @inline()
- final def ==(arg0: Any): Boolean
Test two objects for equality.
Test two objects for equality. The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- Any
- final def addString(b: mutable.StringBuilder): b.type
Appends all elements of this collection to a string builder.
Appends all elements of this collection to a string builder. The written text consists of the string representations (w.r.t. the method
toString
) of all elements of this collection without any separator string.Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> val h = a.addString(b) h: StringBuilder = 1234
- b
the string builder to which elements are appended.
- returns
the string builder
b
to which elements were appended.
- Annotations
- @inline()
- final def addString(b: mutable.StringBuilder, sep: String): b.type
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 stringsep
.Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> a.addString(b, ", ") res0: StringBuilder = 1, 2, 3, 4
- b
the string builder to which elements are appended.
- sep
the separator string.
- returns
the string builder
b
to which elements were appended.
- Annotations
- @inline()
- def addString(b: mutable.StringBuilder, start: String, sep: String, end: String): b.type
Appends all elements of this collection to a string builder using start, end, and separator strings.
Appends all elements of this collection to a string builder using start, end, and separator strings. The written text begins with the string
start
and ends with the stringend
. Inside, the string representations (w.r.t. the methodtoString
) of all elements of this collection are separated by the stringsep
.Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> a.addString(b , "List(" , ", " , ")") res5: StringBuilder = List(1, 2, 3, 4)
- b
the string builder to which elements are appended.
- start
the starting string.
- sep
the separator string.
- end
the ending string.
- returns
the string builder
b
to which elements were appended.
- final def asInstanceOf[T0]: T0
Forces the compiler to treat the receiver object as having type
T0
, even though doing so may violate type safety.Forces the compiler to treat the receiver object as having type
T0
, even though doing so may violate type safety.This method is useful when you believe you have type information the compiler doesn't, and it also isn't possible to check the type at runtime. In such situations, skipping type safety is the only option.
It is platform dependent whether
asInstanceOf
has any effect at runtime. It might do a runtime type test on the erasure ofT0
, insert a conversion (such as boxing/unboxing), fill in a default value, or do nothing at all.In particular,
asInstanceOf
is not a type test. It does **not** mean:this match { case x: T0 => x case _ => throw ClassCastException("...")
Use pattern matching or isInstanceOf for type testing instead.
Situations where
asInstanceOf
is useful:- when flow analysis fails to deduce
T0
automatically - when down-casting a type parameter or an abstract type member (which cannot be checked at runtime due to type erasure) If there is any doubt and you are able to type test instead, you should do so.
Be careful of using
asInstanceOf
whenT0
is a primitive type. WhenT0
is primitive,asInstanceOf
may insert a conversion instead of a type test. If your intent is to convert, use atoT
method (x.toChar
,x.toByte
, etc.).- returns
the receiver object.
- Definition Classes
- Any
- Exceptions thrown
ClassCastException
if the receiver is not an instance of the erasure ofT0
, if that can be checked on this platform
- when flow analysis fails to deduce
- def collectFirst[B](pf: PartialFunction[A, B]): Option[B]
Finds the first element of the collection for which the given partial function is defined, and applies the partial function to it.
Finds the first element of the collection for which the given partial function is defined, and applies the partial function to it.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- pf
the partial function
- returns
an option value containing pf applied to the first value for which it is defined, or
None
if none exists.
Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
Example: - 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 indexstart
with at mostlen
elements of this collection.Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached, or
len
elements have been copied.- B
the type of the elements of the array.
- xs
the array to fill.
- start
the starting index of xs.
- len
the maximal number of elements to copy.
- returns
the number of elements written to the array
- Note
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
- def copyToArray[B >: A](xs: Array[B], start: Int): Int
Copies elements to an array, returning the number of elements written.
Copies elements to an array, returning the number of elements written.
Fills the given array
xs
starting at indexstart
with values of this collection.Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.
- B
the type of the elements of the array.
- xs
the array to fill.
- start
the starting index of xs.
- returns
the number of elements written to the array
- Annotations
- @deprecatedOverriding()
- Note
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
- def copyToArray[B >: A](xs: Array[B]): Int
Copies elements to an array, returning the number of elements written.
Copies elements to an array, returning the number of elements written.
Fills the given array
xs
starting at indexstart
with values of this collection.Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.
- B
the type of the elements of the array.
- xs
the array to fill.
- returns
the number of elements written to the array
- Annotations
- @deprecatedOverriding()
- Note
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
- def corresponds[B](that: IterableOnce[B])(p: (A, B) => Boolean): Boolean
Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.
Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.
Note: will not terminate for infinite-sized collections.
- B
the type of the elements of
that
- that
the other collection
- p
the test predicate, which relates elements from both collections
- returns
true
if both collections have the same length andp(x, y)
istrue
for all corresponding elementsx
of this iterator andy
ofthat
, otherwisefalse
- def count(p: (A) => Boolean): Int
Counts the number of elements in the collection which satisfy a predicate.
Counts the number of elements in the collection which satisfy a predicate.
Note: will not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
the number of elements satisfying the predicate
p
.
- def ensuring(cond: (IterableOnceOps[A, CC, C]) => Boolean, msg: => Any): IterableOnceOps[A, CC, C]
- Implicit
- This member is added by an implicit conversion from IterableOnceOps[A, CC, C] toEnsuring[IterableOnceOps[A, CC, C]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: (IterableOnceOps[A, CC, C]) => Boolean): IterableOnceOps[A, CC, C]
- Implicit
- This member is added by an implicit conversion from IterableOnceOps[A, CC, C] toEnsuring[IterableOnceOps[A, CC, C]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: Boolean, msg: => Any): IterableOnceOps[A, CC, C]
- Implicit
- This member is added by an implicit conversion from IterableOnceOps[A, CC, C] toEnsuring[IterableOnceOps[A, CC, C]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: Boolean): IterableOnceOps[A, CC, C]
- Implicit
- This member is added by an implicit conversion from IterableOnceOps[A, CC, C] toEnsuring[IterableOnceOps[A, CC, C]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def equals(arg0: Any): Boolean
Compares the receiver object (
this
) with the argument object (that
) for equivalence.Compares the receiver object (
this
) with the argument object (that
) for equivalence.Any implementation of this method should be an equivalence relation:
- It is reflexive: for any instance
x
of typeAny
,x.equals(x)
should returntrue
. - It is symmetric: for any instances
x
andy
of typeAny
,x.equals(y)
should returntrue
if and only ify.equals(x)
returnstrue
. - It is transitive: for any instances
x
,y
, andz
of typeAny
ifx.equals(y)
returnstrue
andy.equals(z)
returnstrue
, thenx.equals(z)
should returntrue
.
If you override this method, you should verify that your implementation remains an equivalence relation. Additionally, when overriding this method it is usually necessary to override
hashCode
to ensure that objects which are "equal" (o1.equals(o2)
returnstrue
) hash to the same scala.Int. (o1.hashCode.equals(o2.hashCode)
).- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- Any
- It is reflexive: for any instance
- def exists(p: (A) => Boolean): Boolean
Tests whether a predicate holds for at least one element of this collection.
Tests whether a predicate holds for at least one element of this collection.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
true
if the given predicatep
is satisfied by at least one element of this collection, otherwisefalse
- def find(p: (A) => Boolean): Option[A]
Finds the first element of the collection satisfying a predicate, if any.
Finds the first element of the collection satisfying a predicate, if any.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- p
the predicate used to test elements.
- returns
an option value containing the first element in the collection that satisfies
p
, orNone
if none exists.
- def fold[A1 >: A](z: A1)(op: (A1, A1) => A1): A1
Applies the given binary operator
op
to the given initial valuez
and all elements of this collection.Applies the given binary operator
op
to the given initial valuez
and all elements of this collection.For each application of the operator, each operand is either an element of this collection, the initial value, or another such application of the operator.
The order of applications of the operator is unspecified and may be nondeterministic. Each element appears exactly once in the computation. The initial value may be used an arbitrary number of times, but at least once.
If this collection is ordered, then for any application of the operator, the element(s) appearing in the left operand will precede those in the right.
Note: might return different results for different runs, unless either of the following conditions is met: (1) the operator is associative, and the underlying collection type is ordered; or (2) the operator is associative and commutative. In either case, it is also necessary that the initial value be a neutral value for the operator, e.g.
Nil
forList
concatenation or1
for multiplication.The default implementation in
IterableOnce
is equivalent tofoldLeft
but may be overridden for more efficient traversal orders.Note: will not terminate for infinite-sized collections.
- A1
The type parameter for the binary operator, a supertype of
A
.- z
An initial value; may be used an arbitrary number of times in the computation of the result; must be a neutral value for
op
for the result to always be the same across runs.- op
A binary operator; must be associative for the result to always be the same across runs.
- returns
The result of applying
op
between all the elements andz
, orz
if this collection is empty.
- def foldLeft[B](z: B)(op: (B, A) => B): B
Applies the given binary operator
op
to the given initial valuez
and all elements of this collection, going left to right.Applies the given binary operator
op
to the given initial valuez
and all elements of this collection, going left to right. Returns the initial value if this collection is empty."Going left to right" only makes sense if this collection is ordered: then if
x_{1}
,x_{2}
, ...,x_{n}
are the elements of this collection, the result isop( op( ... op( op(z, x_{1}), x_{2}) ... ), x_{n})
.If this collection is not ordered, then for each application of the operator, each right operand is an element. In addition, the leftmost operand is the initial value, and each other left operand is itself an application of the operator. The elements of this collection and the initial value all appear exactly once in the computation.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Note: will not terminate for infinite-sized collections.
- B
The result type of the binary operator.
- z
An initial value.
- op
A binary operator.
- returns
The result of applying
op
toz
and all elements of this collection, going left to right. Returnsz
if this collection is empty.
- def foldRight[B](z: B)(op: (A, B) => B): B
Applies the given binary operator
op
to all elements of this collection and the given initial valuez
, going right to left.Applies the given binary operator
op
to all elements of this collection and the given initial valuez
, going right to left. Returns the initial value if this collection is empty."Going right to left" only makes sense if this collection is ordered: then if
x_{1}
,x_{2}
, ...,x_{n}
are the elements of this collection, the result isop(x_{1}, op(x_{2}, op( ... op(x_{n}, z) ... )))
.If this collection is not ordered, then for each application of the operator, each left operand is an element. In addition, the rightmost operand is the initial value, and each other right operand is itself an application of the operator. The elements of this collection and the initial value all appear exactly once in the computation.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Note: will not terminate for infinite-sized collections.
- B
The result type of the binary operator.
- z
An initial value.
- op
A binary operator.
- returns
The result of applying
op
to all elements of this collection andz
, going right to left. Returnsz
if this collection is empty.
- def forall(p: (A) => Boolean): Boolean
Tests whether a predicate holds for all elements of this collection.
Tests whether a predicate holds for all elements of this collection.
Note: may not terminate for infinite-sized collections.
- p
the predicate used to test elements.
- returns
true
if this collection is empty or the given predicatep
holds for all elements of this collection, otherwisefalse
.
- def foreach[U](f: (A) => U): Unit
Applies
f
to each element for its side effects.Applies
f
to each element for its side effects. Note:U
parameter needed to help scalac's type inference. - def hashCode(): Int
Calculate a hash code value for the object.
Calculate a hash code value for the object.
The default hashing algorithm is platform dependent.
Note that it is allowed for two objects to have identical hash codes (
o1.hashCode.equals(o2.hashCode)
) yet not be equal (o1.equals(o2)
returnsfalse
). A degenerate implementation could always return0
. However, it is required that if two objects are equal (o1.equals(o2)
returnstrue
) that they have identical hash codes (o1.hashCode.equals(o2.hashCode)
). Therefore, when overriding this method, be sure to verify that the behavior is consistent with theequals
method.- returns
the hash code value for this object.
- Definition Classes
- Any
- def isEmpty: Boolean
Tests whether the collection is empty.
Tests whether the collection is empty.
Note: The default implementation creates and discards an iterator.
Note: Implementations in subclasses that are not repeatedly iterable must take care not to consume any elements when
isEmpty
is called.- returns
true
if the collection contains no elements,false
otherwise.
- final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object has the same erasure as
T0
.Test whether the dynamic type of the receiver object has the same erasure as
T0
.Depending on what
T0
is, the test is done in one of the below ways:T0
is a non-parameterized class type, e.g.BigDecimal
: this method returnstrue
if the value of the receiver object is aBigDecimal
or a subtype ofBigDecimal
.T0
is a parameterized class type, e.g.List[Int]
: this method returnstrue
if the value of the receiver object is someList[X]
for anyX
. For example,List(1, 2, 3).isInstanceOf[List[String]]
will return true.T0
is some singleton typex.type
or literalx
: this method returnsthis.eq(x)
. For example,x.isInstanceOf[1]
is equivalent tox.eq(1)
T0
is an intersectionX with Y
orX & Y: this method is equivalent to
x.isInstanceOf[X] && x.isInstanceOf[Y]T0
is a unionX | Y
: this method is equivalent tox.isInstanceOf[X] || x.isInstanceOf[Y]
T0
is a type parameter or an abstract type member: this method is equivalent toisInstanceOf[U]
whereU
isT0
's upper bound,Any
ifT0
is unbounded. For example,x.isInstanceOf[A]
whereA
is an unbounded type parameter will return true for any value ofx
.
This is exactly equivalent to the type pattern
_: T0
- returns
true
if the receiver object is an instance of erasure of typeT0
;false
otherwise.
- Definition Classes
- Any
- Note
due to the unexpectedness of
List(1, 2, 3).isInstanceOf[List[String]]
returning true andx.isInstanceOf[A]
whereA
is a type parameter or abstract member returning true, these forms issue a warning.
- def isTraversableAgain: Boolean
Tests whether this collection can be repeatedly traversed.
Tests whether this collection can be repeatedly traversed. Always true for Iterables and false for Iterators unless overridden.
- returns
true
if it is repeatedly traversable,false
otherwise.
- def max[B >: A](implicit ord: math.Ordering[B]): A
Finds the largest element.
Finds the largest element.
Note: will not terminate for infinite-sized collections.
- B
The type over which the ordering is defined.
- ord
An ordering to be used for comparing elements.
- returns
the largest element of this collection with respect to the ordering
ord
.
- Exceptions thrown
UnsupportedOperationException
if this collection is empty.
- def maxBy[B](f: (A) => B)(implicit ord: math.Ordering[B]): A
Finds the first element which yields the largest value measured by function
f
.Finds the first element which yields the largest value measured by function
f
.Note: will not terminate for infinite-sized collections.
- B
The result type of the function
f
.- f
The measuring function.
- returns
the first element of this collection with the largest value measured by function
f
with respect to the orderingcmp
.
- Exceptions thrown
UnsupportedOperationException
if this collection is empty.
- def maxByOption[B](f: (A) => B)(implicit ord: math.Ordering[B]): Option[A]
Finds the first element which yields the largest value measured by function
f
.Finds the first element which yields the largest value measured by function
f
.Note: will not terminate for infinite-sized collections.
- B
The result type of the function
f
.- f
The measuring function.
- returns
an option value containing the first element of this collection with the largest value measured by function
f
with respect to the orderingcmp
.
- def maxOption[B >: A](implicit ord: math.Ordering[B]): Option[A]
Finds the largest element.
Finds the largest element.
Note: will not terminate for infinite-sized collections.
- B
The type over which the ordering is defined.
- ord
An ordering to be used for comparing elements.
- returns
an option value containing the largest element of this collection with respect to the ordering
ord
.
- def min[B >: A](implicit ord: math.Ordering[B]): A
Finds the smallest element.
Finds the smallest element.
Note: will not terminate for infinite-sized collections.
- B
The type over which the ordering is defined.
- ord
An ordering to be used for comparing elements.
- returns
the smallest element of this collection with respect to the ordering
ord
.
- Exceptions thrown
UnsupportedOperationException
if this collection is empty.
- def minBy[B](f: (A) => B)(implicit ord: math.Ordering[B]): A
Finds the first element which yields the smallest value measured by function
f
.Finds the first element which yields the smallest value measured by function
f
.Note: will not terminate for infinite-sized collections.
- B
The result type of the function
f
.- f
The measuring function.
- returns
the first element of this collection with the smallest value measured by function
f
with respect to the orderingcmp
.
- Exceptions thrown
UnsupportedOperationException
if this collection is empty.
- def minByOption[B](f: (A) => B)(implicit ord: math.Ordering[B]): Option[A]
Finds the first element which yields the smallest value measured by function
f
.Finds the first element which yields the smallest value measured by function
f
.Note: will not terminate for infinite-sized collections.
- B
The result type of the function
f
.- f
The measuring function.
- returns
an option value containing the first element of this collection with the smallest value measured by function
f
with respect to the orderingcmp
.
- def minOption[B >: A](implicit ord: math.Ordering[B]): Option[A]
Finds the smallest element.
Finds the smallest element.
Note: will not terminate for infinite-sized collections.
- B
The type over which the ordering is defined.
- ord
An ordering to be used for comparing elements.
- returns
an option value containing the smallest element of this collection with respect to the ordering
ord
.
- final def mkString: String
Displays all elements of this collection in a string.
Displays all elements of this collection in a string.
Delegates to addString, which can be overridden.
- returns
a string representation of this collection. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this collection follow each other without any separator string.
- Annotations
- @inline()
- final def mkString(sep: String): String
Displays all elements of this collection in a string using a separator string.
Displays all elements of this collection in a string using a separator string.
Delegates to addString, which can be overridden.
- sep
the separator string.
- returns
a string representation of this collection. In the resulting string the string representations (w.r.t. the method
toString
) of all elements of this collection are separated by the stringsep
.
- Annotations
- @inline()
List(1, 2, 3).mkString("|") = "1|2|3"
Example: - final def mkString(start: String, sep: String, end: String): String
Displays all elements of this collection in a string using start, end, and separator strings.
Displays all elements of this collection in a string using start, end, and separator strings.
Delegates to addString, which can be overridden.
- start
the starting string.
- sep
the separator string.
- end
the ending string.
- returns
a string representation of this collection. The resulting string begins with the string
start
and ends with the stringend
. Inside, the string representations (w.r.t. the methodtoString
) of all elements of this collection are separated by the stringsep
.
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Example: - def nonEmpty: Boolean
Tests whether the collection is not empty.
Tests whether the collection is not empty.
- returns
true
if the collection contains at least one element,false
otherwise.
- Annotations
- @deprecatedOverriding()
- def product[B >: A](implicit num: math.Numeric[B]): B
Multiplies together the elements of this collection.
Multiplies together the elements of this collection.
The default implementation uses
reduce
for a known non-empty collection,foldLeft
otherwise.Note: will not terminate for infinite-sized collections.
- B
the result type of the
*
operator.- num
an implicit parameter defining a set of numeric operations which includes the
*
operator to be used in forming the product.- returns
the product of all elements of this collection with respect to the
*
operator innum
.
- def reduce[B >: A](op: (B, B) => B): B
Applies the given binary operator
op
to all elements of this collection.Applies the given binary operator
op
to all elements of this collection.For each application of the operator, each operand is either an element of this collection or another such application of the operator. The order of applications of the operator is unspecified and may be nondeterministic. Each element appears exactly once in the computation.
If this collection is ordered, then for any application of the operator, the element(s) appearing in the left operand will precede those in the right.
Note: might return different results for different runs, unless either of the following conditions is met: (1) the operator is associative, and the underlying collection type is ordered; or (2) the operator is associative and commutative.
Note: will not terminate for infinite-sized collections.
- B
The type parameter for the binary operator, a supertype of
A
.- op
A binary operator; must be associative for the result to always be the same across runs.
- returns
The result of applying
op
between all the elements if the collection is nonempty.
- Exceptions thrown
UnsupportedOperationException
if this collection is empty.
- def reduceLeft[B >: A](op: (B, A) => B): B
Applies the given binary operator
op
to all elements of this collection, going left to right.Applies the given binary operator
op
to all elements of this collection, going left to right."Going left to right" only makes sense if this collection is ordered: then if
x_{1}
,x_{2}
, ...,x_{n}
are the elements of this collection, the result isop( op( op( ... op(x_{1}, x_{2}) ... ), x_{n-1}), x_{n})
.If this collection is not ordered, then for each application of the operator, each right operand is an element. In addition, the leftmost operand is the first element of this collection and each other left operand is itself an application of the operator. Each element appears exactly once in the computation.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
Note: will not terminate for infinite-sized collections.
- B
The result type of the binary operator, a supertype of
A
.- op
A binary operator.
- returns
The result of applying
op
to all elements of this collection, going left to right.
- Exceptions thrown
UnsupportedOperationException
if this collection is empty.
- def reduceLeftOption[B >: A](op: (B, A) => B): Option[B]
If this collection is nonempty, reduces it with the given binary operator
op
, going left to right.If this collection is nonempty, reduces it with the given binary operator
op
, going left to right.The behavior is the same as reduceLeft except that the value is
None
if the collection is empty. Each element appears exactly once in the computation.Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
Note: will not terminate for infinite-sized collections.
- B
The result type of the binary operator, a supertype of
A
.- op
A binary operator.
- returns
The result of reducing this collection with
op
going left to right if the collection is nonempty, inside aSome
, andNone
otherwise.
- def reduceOption[B >: A](op: (B, B) => B): Option[B]
If this collection is nonempty, reduces it with the given binary operator
op
.If this collection is nonempty, reduces it with the given binary operator
op
.The behavior is the same as reduce except that the value is
None
if the collection is empty. The order of applications of the operator is unspecified and may be nondeterministic. Each element appears exactly once in the computation.Note: might return different results for different runs, unless either of the following conditions is met: (1) the operator is associative, and the underlying collection type is ordered; or (2) the operator is associative and commutative.
Note: will not terminate for infinite-sized collections.
- B
A type parameter for the binary operator, a supertype of
A
.- op
A binary operator; must be associative for the result to always be the same across runs.
- returns
The result of reducing this collection with
op
if the collection is nonempty, inside aSome
, andNone
otherwise.
- def reduceRight[B >: A](op: (A, B) => B): B
Applies the given binary operator
op
to all elements of this collection, going right to left.Applies the given binary operator
op
to all elements of this collection, going right to left."Going right to left" only makes sense if this collection is ordered: then if
x_{1}
,x_{2}
, ...,x_{n}
are the elements of this collection, the result isop(x_{1}, op(x_{2}, op( ... op(x_{n-1}, x_{n}) ... )))
.If this collection is not ordered, then for each application of the operator, each left operand is an element. In addition, the rightmost operand is the last element of this collection and each other right operand is itself an application of the operator. Each element appears exactly once in the computation.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
Note: will not terminate for infinite-sized collections.
- B
The result type of the binary operator, a supertype of
A
.- op
A binary operator.
- returns
The result of applying
op
to all elements of this collection, going right to left.
- Exceptions thrown
UnsupportedOperationException
if this collection is empty.
- def reduceRightOption[B >: A](op: (A, B) => B): Option[B]
If this collection is nonempty, reduces it with the given binary operator
op
, going right to left.If this collection is nonempty, reduces it with the given binary operator
op
, going right to left.The behavior is the same as reduceRight except that the value is
None
if the collection is empty. Each element appears exactly once in the computation.Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
Note: will not terminate for infinite-sized collections.
- B
The result type of the binary operator, a supertype of
A
.- op
A binary operator.
- returns
The result of reducing this collection with
op
going right to left if the collection is nonempty, inside aSome
, andNone
otherwise.
- def reversed: Iterable[A]
- Attributes
- protected
- def size: Int
The size of this collection.
The size of this collection.
Note: will not terminate for infinite-sized collections.
- returns
the number of elements in this collection.
- def splitAt(n: Int): (C, C)
Splits this collection into a prefix/suffix pair at a given position.
Splits this collection into a prefix/suffix pair at a given position.
Note:
c splitAt n
is equivalent to (but possibly more efficient than)(c take n, c drop n)
.Note: might return different results for different runs, unless the underlying collection type is ordered.
- n
the position at which to split.
- returns
a pair of collections consisting of the first
n
elements of this collection, and the other elements.
- def sum[B >: A](implicit num: math.Numeric[B]): B
Sums the elements of this collection.
Sums the elements of this collection.
The default implementation uses
reduce
for a known non-empty collection,foldLeft
otherwise.Note: will not terminate for infinite-sized collections.
- B
the result type of the
+
operator.- num
an implicit parameter defining a set of numeric operations which includes the
+
operator to be used in forming the sum.- returns
the sum of all elements of this collection with respect to the
+
operator innum
.
- def to[C1](factory: Factory[A, C1]): C1
Given a collection factory
factory
, converts this collection to the appropriate representation for the current element typeA
.Given a collection factory
factory
, converts this collection to the appropriate representation for the current element typeA
. Example uses:xs.to(List) xs.to(ArrayBuffer) xs.to(BitSet) // for xs: Iterable[Int]
- def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]
Converts this collection to an
Array
.Converts this collection to an
Array
.Implementation note: DO NOT call Array.from from this method.
- B
The type of elements of the result, a supertype of
A
.- returns
This collection as an
Array[B]
.
- final def toBuffer[B >: A]: Buffer[B]
Converts this collection to a
Buffer
.Converts this collection to a
Buffer
.- B
The type of elements of the result, a supertype of
A
.- returns
This collection as a
Buffer[B]
.
- Annotations
- @inline()
- def toIndexedSeq: immutable.IndexedSeq[A]
Converts this collection to an
IndexedSeq
.Converts this collection to an
IndexedSeq
.- returns
This collection as an
IndexedSeq[A]
.
- def toList: immutable.List[A]
Converts this collection to a
List
.Converts this collection to a
List
.- returns
This collection as a
List[A]
.
- def toMap[K, V](implicit ev: <:<[A, (K, V)]): immutable.Map[K, V]
Converts this collection to a
Map
, given an implicit coercion from the collection's type to a key-value tuple.Converts this collection to a
Map
, given an implicit coercion from the collection's type to a key-value tuple.- K
The key type for the resulting map.
- V
The value type for the resulting map.
- ev
An implicit coercion from
A
to[K, V]
.- returns
This collection as a
Map[K, V]
.
- def toSeq: immutable.Seq[A]
- returns
This collection as a
Seq[A]
. This is equivalent toto(Seq)
but might be faster.
- def toSet[B >: A]: immutable.Set[B]
Converts this collection to a
Set
.Converts this collection to a
Set
.- B
The type of elements of the result, a supertype of
A
.- returns
This collection as a
Set[B]
.
- def toString(): String
Returns a string representation of the object.
Returns a string representation of the object.
The default representation is platform dependent.
- returns
a string representation of the object.
- Definition Classes
- Any
- def toVector: immutable.Vector[A]
Converts this collection to a
Vector
.Converts this collection to a
Vector
.- returns
This collection as a
Vector[A]
.
Deprecated Value Members
- final def /:[B](z: B)(op: (B, A) => B): B
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.13.0) Use foldLeft instead of /:
- final def :\[B](z: B)(op: (A, B) => B): B
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.13.0) Use foldRight instead of :\
- def aggregate[B](z: => B)(seqop: (B, A) => B, combop: (B, B) => B): B
Aggregates the results of applying an operator to subsequent elements.
Aggregates the results of applying an operator to subsequent elements.
Since this method degenerates to
foldLeft
for sequential (non-parallel) collections, where the combining operation is ignored, it is advisable to preferfoldLeft
for that case.For parallel collections, use the
aggregate
method specified byscala.collection.parallel.ParIterableLike
.- B
the result type, produced by
seqop
,combop
, and by this function as a final result.- z
the start value, a neutral element for
seqop
.- seqop
the binary operator used to accumulate the result.
- combop
an associative operator for combining sequential results, unused for sequential collections.
- Annotations
- @deprecated
- Deprecated
(Since version 2.13.0) For sequential collections, prefer
foldLeft(z)(seqop)
. For parallel collections, useParIterableLike#aggregate
.
- final def copyToBuffer[B >: A](dest: Buffer[B]): Unit
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.13.0) Use
dest ++= coll
instead
- def formatted(fmtstr: String): String
Returns string formatted according to given
format
string.Returns string formatted according to given
format
string. Format strings are as forString.format
(@see java.lang.String.format).- Implicit
- This member is added by an implicit conversion from IterableOnceOps[A, CC, C] toStringFormat[IterableOnceOps[A, CC, C]] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.12.16) Use
formatString.format(value)
instead ofvalue.formatted(formatString)
, or use thef""
string interpolator. In Java 15 and later,formatted
resolves to the new method in String which has reversed parameters.
- def hasDefiniteSize: Boolean
Tests whether this collection is known to have a finite size.
Tests whether this collection 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 returnstrue
if all elements have been computed. It returnsfalse
if the stream is not yet evaluated to the end. Non-empty Iterators usually returnfalse
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
returnstrue
. However, checkinghasDefiniteSize
can provide an assurance that size is well-defined and non-termination is not a concern.- returns
true
if this collection is known to have finite size,false
otherwise.
- Annotations
- @deprecated
- Deprecated
(Since version 2.13.0) Check .knownSize instead of .hasDefiniteSize for more actionable information (see scaladoc for details)
- See also
method
knownSize
for a more useful alternative
- final def toIterator: Iterator[A]
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.13.0) Use .iterator instead of .toIterator
- final def toStream: immutable.Stream[A]
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.13.0) Use .to(LazyList) instead of .toStream
- def →[B](y: B): (IterableOnceOps[A, CC, C], B)
- Implicit
- This member is added by an implicit conversion from IterableOnceOps[A, CC, C] toArrowAssoc[IterableOnceOps[A, CC, C]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @deprecated
- Deprecated
(Since version 2.13.0) Use
->
instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int
,Float
,Array
orOption
which are accessible in all Scala compilation units without explicit qualification or imports.Notable packages include:
scala.collection
and its sub-packages contain Scala's collections frameworkscala.collection.immutable
- Immutable, sequential data-structures such asVector
,List
,Range
,HashMap
orHashSet
scala.collection.mutable
- Mutable, sequential data-structures such asArrayBuffer
,StringBuilder
,HashMap
orHashSet
scala.collection.concurrent
- Mutable, concurrent data-structures such asTrieMap
scala.concurrent
- Primitives for concurrent programming such asFutures
andPromises
scala.io
- Input and output operationsscala.math
- Basic math functions and additional numeric types likeBigInt
andBigDecimal
scala.sys
- Interaction with other processes and the operating systemscala.util.matching
- Regular expressionsOther packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
scala.reflect
- Scala's reflection API (scala-reflect.jar)scala.xml
- XML parsing, manipulation, and serialization (scala-xml.jar)scala.collection.parallel
- Parallel collections (scala-parallel-collections.jar)scala.util.parsing
- Parser combinators (scala-parser-combinators.jar)scala.swing
- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)Automatic imports
Identifiers in the scala package and the
scala.Predef
object are always in scope by default.Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example,
List
is an alias forscala.collection.immutable.List
.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
String
is an alias forjava.lang.String
.