Packages

  • package root

    This is the documentation for the Scala standard library.

    This is the documentation for the Scala standard library.

    Package structure

    The scala package contains core types like Int, Float, Array or Option which are accessible in all Scala compilation units without explicit qualification or imports.

    Notable packages include:

    Other 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.swing - A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)
    • scala.util.parsing - Parser combinators (scala-parser-combinators.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 for scala.collection.immutable.List.

    Other aliases refer to classes provided by the underlying platform. For example, on the JVM, String is an alias for java.lang.String.

    Definition Classes
    root
  • package scala

    Core Scala types.

    Core Scala types. They are always available without an explicit import.

    Definition Classes
    root
  • package collection

    Contains the base traits and objects needed to use and extend Scala's collection library.

    Contains the base traits and objects needed to use and extend Scala's collection library.

    Guide

    A detailed guide for using the collections library is available at http://docs.scala-lang.org/overviews/collections/introduction.html. Developers looking to extend the collections library can find a description of its architecture at http://docs.scala-lang.org/overviews/core/architecture-of-scala-collections.html.

    Using Collections

    It is convenient to treat all collections as either a scala.collection.Traversable or scala.collection.Iterable, as these traits define the vast majority of operations on a collection.

    Collections can, of course, be treated as specifically as needed, and the library is designed to ensure that the methods that transform collections will return a collection of the same type:

    scala> val array = Array(1,2,3,4,5,6)
    array: Array[Int] = Array(1, 2, 3, 4, 5, 6)
    
    scala> array map { _.toString }
    res0: Array[String] = Array(1, 2, 3, 4, 5, 6)
    
    scala> val list = List(1,2,3,4,5,6)
    list: List[Int] = List(1, 2, 3, 4, 5, 6)
    
    scala> list map { _.toString }
    res1: List[String] = List(1, 2, 3, 4, 5, 6)

    Creating Collections

    The most common way to create a collection is to use its companion object as a factory. The three most commonly used collections are scala.collection.Seq, scala.collection.immutable.Set, and scala.collection.immutable.Map. They can be used directly as shown below since their companion objects are all available as type aliases in either the scala package or in scala.Predef. New collections are created like this:

    scala> val seq = Seq(1,2,3,4,1)
    seq: Seq[Int] = List(1, 2, 3, 4, 1)
    
    scala> val set = Set(1,2,3,4,1)
    set: scala.collection.immutable.Set[Int] = Set(1, 2, 3, 4)
    
    scala> val map = Map(1 -> "one", 2 -> "two", 3 -> "three", 2 -> "too")
    map: scala.collection.immutable.Map[Int,String] = Map(1 -> one, 2 -> too, 3 -> three)

    It is also typical to prefer the scala.collection.immutable collections over those in scala.collection.mutable; the types aliased in the scala.Predef object are the immutable versions.

    Also note that the collections library was carefully designed to include several implementations of each of the three basic collection types. These implementations have specific performance characteristics which are described in the guide.

    The concrete parallel collections also have specific performance characteristics which are described in the parallel collections guide

    Converting to and from Java Collections

    The scala.collection.JavaConverters object provides a collection of decorators that allow converting between Scala and Java collections using asScala and asJava methods.

    Definition Classes
    scala
  • trait IterableViewLike[+A, +Coll, +This <: IterableView[A, Coll] with IterableViewLike[A, Coll, This]] extends Iterable[A] with IterableLike[A, This] with TraversableView[A, Coll] with TraversableViewLike[A, Coll, This]

    A template trait for non-strict views of iterable collections.

    A template trait for non-strict views of iterable collections.

    A view is a lazy version of some collection. Collection transformers such as map or filter or ++ do not traverse any elements when applied on a view. Instead they create a new view which simply records that fact that the operation needs to be applied. The collection elements are accessed, and the view operations are applied, when a non-view result is needed, or when the force method is called on a view. All views for iterable collections are defined by re-interpreting the iterator method.

    Definition Classes
    collection
  • Appended
  • DroppedWhile
  • EmptyView
  • Filtered
  • FlatMapped
  • Forced
  • Mapped
  • Prepended
  • Sliced
  • TakenWhile
  • Transformed
  • WithFilter
  • Zipped
  • ZippedAll

trait Mapped[B] extends IterableViewLike.Mapped[B] with Transformed[B]

Source
IterableViewLike.scala
Linear Supertypes
Transformed[B], IterableView[B, Coll], IterableViewLike[B, Coll, IterableView[B, Coll]], Iterable[B], IterableLike[B, IterableView[B, Coll]], Equals, GenIterable[B], GenIterableLike[B, IterableView[B, Coll]], IterableViewLike.Mapped[B], IterableViewLike.Transformed[B], TraversableView[B, Coll], TraversableViewLike[B, Coll, IterableView[B, Coll]], ViewMkString[B], Traversable[B], GenTraversable[B], GenericTraversableTemplate[B, Iterable], TraversableLike[B, IterableView[B, Coll]], GenTraversableLike[B, IterableView[B, Coll]], Parallelizable[B, ParIterable[B]], TraversableOnce[B], GenTraversableOnce[B], FilterMonadic[B, IterableView[B, Coll]], HasNewBuilder[B, IterableView[B, Coll]], AnyRef, Any
Known Subclasses
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. Mapped
  2. Transformed
  3. IterableView
  4. IterableViewLike
  5. Iterable
  6. IterableLike
  7. Equals
  8. GenIterable
  9. GenIterableLike
  10. Mapped
  11. Transformed
  12. TraversableView
  13. TraversableViewLike
  14. ViewMkString
  15. Traversable
  16. GenTraversable
  17. GenericTraversableTemplate
  18. TraversableLike
  19. GenTraversableLike
  20. Parallelizable
  21. TraversableOnce
  22. GenTraversableOnce
  23. FilterMonadic
  24. HasNewBuilder
  25. AnyRef
  26. Any
Implicitly
  1. by CollectionsHaveToParArray
  2. by MonadOps
  3. by any2stringadd
  4. by StringFormat
  5. by Ensuring
  6. by ArrowAssoc
  7. by alternateImplicit
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Visibility
  1. Public
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Type Members

  1. trait Appended[B >: A] extends IterableViewLike.Appended[B] with Transformed[B]
    Definition Classes
    IterableViewLike
  2. trait DroppedWhile extends IterableViewLike.DroppedWhile with Transformed[A]
    Definition Classes
    IterableViewLike
  3. trait EmptyView extends Transformed[Nothing] with IterableViewLike.EmptyView
    Definition Classes
    IterableViewLike
  4. trait Filtered extends IterableViewLike.Filtered with Transformed[A]
    Definition Classes
    IterableViewLike
  5. trait FlatMapped[B] extends IterableViewLike.FlatMapped[B] with Transformed[B]
    Definition Classes
    IterableViewLike
  6. trait Forced[B] extends IterableViewLike.Forced[B] with Transformed[B]
    Definition Classes
    IterableViewLike
  7. trait Mapped[B] extends IterableViewLike.Mapped[B] with Transformed[B]
    Definition Classes
    IterableViewLike
  8. trait Prepended[B >: A] extends IterableViewLike.Prepended[B] with Transformed[B]
    Definition Classes
    IterableViewLike
  9. trait Sliced extends IterableViewLike.Sliced with Transformed[A]
    Definition Classes
    IterableViewLike
  10. trait TakenWhile extends IterableViewLike.TakenWhile with Transformed[A]
    Definition Classes
    IterableViewLike
  11. trait Transformed[+B] extends IterableView[B, Coll] with IterableViewLike.Transformed[B]
    Definition Classes
    IterableViewLike
  12. trait Zipped[B] extends Transformed[(A, B)]
    Definition Classes
    IterableViewLike
  13. trait ZippedAll[A1 >: A, B] extends Transformed[(A1, B)]
    Definition Classes
    IterableViewLike
  14. class WithFilter extends FilterMonadic[A, Repr]

    A class supporting filtered operations.

    A class supporting filtered operations. Instances of this class are returned by method withFilter.

    Definition Classes
    TraversableLike

Concrete Value Members

  1. def ++[B >: B, That](xs: GenTraversableOnce[B])(implicit bf: CanBuildFrom[IterableView[B, Coll], B, That]): That

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

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

    B

    the element type of the returned collection.

    That

    the class of the returned collection. Where possible, That is the same class as the current collection class Repr, but this depends on the element type B being admissible for that class, which means that an implicit instance of type CanBuildFrom[Repr, B, That] is found.

    bf

    an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and the new element type B.

    returns

    a new collection of type That which contains all elements of this collection followed by all elements of that.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
  2. def ++:[B >: B, That](xs: Traversable[B])(implicit bf: CanBuildFrom[IterableView[B, Coll], B, That]): That

    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.

    Example:

    scala> val x = List(1)
    x: List[Int] = List(1)
    
    scala> val y = LinkedList(2)
    y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)
    
    scala> val z = x ++: y
    z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)

    This overload exists because: for the implementation of ++: we should reuse that of ++ because many collections override it with more efficient versions.

    Since TraversableOnce has no ++ method, we have to implement that directly, but Traversable and down can use the overload.

    B

    the element type of the returned collection.

    That

    the class of the returned collection. Where possible, That is the same class as the current collection class Repr, but this depends on the element type B being admissible for that class, which means that an implicit instance of type CanBuildFrom[Repr, B, That] is found.

    bf

    an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and the new element type B.

    returns

    a new collection of type That which contains all elements of this collection followed by all elements of that.

    Definition Classes
    TraversableViewLikeTraversableLike
  3. def ++:[B](that: TraversableOnce[B]): Iterable[B]

    [use case] As with ++, returns a new collection containing the elements from the left operand followed by the elements from the right operand.

    [use case]

    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.

    Example:

    scala> val x = List(1)
    x: List[Int] = List(1)
    
    scala> val y = LinkedList(2)
    y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)
    
    scala> val z = x ++: y
    z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
    B

    the element type of the returned collection.

    that

    the traversable to append.

    returns

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

    Definition Classes
    TraversableViewLikeTraversableLike
    Full Signature

    def ++:[B >: B, That](xs: TraversableOnce[B])(implicit bf: CanBuildFrom[IterableView[B, Coll], B, That]): That

  4. def /:[B](z: B)(op: (B, B) ⇒ B): B

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

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

    Note: /: is alternate syntax for foldLeft; z /: xs is the same as xs foldLeft z.

    Examples:

    Note that the folding function used to compute b is equivalent to that used to compute c.

    scala> val a = List(1,2,3,4)
    a: List[Int] = List(1, 2, 3, 4)
    
    scala> val b = (5 /: a)(_+_)
    b: Int = 15
    
    scala> val c = (5 /: a)((x,y) => x + y)
    c: Int = 15

    Note: will not terminate for infinite-sized collections.

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

    B

    the result type of the binary operator.

    z

    the start value.

    op

    the binary operator.

    returns

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

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

    where x1, ..., xn are the elements of this traversable or iterator.

    Definition Classes
    TraversableOnceGenTraversableOnce
  5. def :\[B](z: B)(op: (B, B) ⇒ B): B

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

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

    Note: :\ is alternate syntax for foldRight; xs :\ z is the same as xs foldRight z.

    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.

    Examples:

    Note that the folding function used to compute b is equivalent to that used to compute c.

    scala> val a = List(1,2,3,4)
    a: List[Int] = List(1, 2, 3, 4)
    
    scala> val b = (a :\ 5)(_+_)
    b: Int = 15
    
    scala> val c = (a :\ 5)((x,y) => x + y)
    c: Int = 15
    B

    the result type of the binary operator.

    z

    the start value

    op

    the binary operator

    returns

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

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

    where x1, ..., xn are the elements of this traversable or iterator.

    Definition Classes
    TraversableOnceGenTraversableOnce
  6. def addString(b: StringBuilder, start: String, sep: String, end: String): StringBuilder
    Definition Classes
    ViewMkString
  7. def addString(b: StringBuilder): StringBuilder

    Appends all elements of this traversable or iterator to a string builder.

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

    Example:

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

    the string builder to which elements are appended.

    returns

    the string builder b to which elements were appended.

    Definition Classes
    TraversableOnce
  8. def addString(b: StringBuilder, sep: String): StringBuilder

    Appends all elements of this traversable or iterator to a string builder using a separator string.

    Appends all elements of this traversable or iterator 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 traversable or iterator, separated by the string sep.

    Example:

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

    the string builder to which elements are appended.

    sep

    the separator string.

    returns

    the string builder b to which elements were appended.

    Definition Classes
    TraversableOnce
  9. def aggregate[B](z: ⇒ B)(seqop: (B, B) ⇒ 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.

    This is a more general form of fold and reduce. It is similar to foldLeft in that it doesn't require the result to be a supertype of the element type. In addition, it allows parallel collections to be processed in chunks, and then combines the intermediate results.

    aggregate splits the traversable or iterator into partitions and processes each partition by sequentially applying seqop, starting with z (like foldLeft). Those intermediate results are then combined by using combop (like fold). The implementation of this operation may operate on an arbitrary number of collection partitions (even 1), so combop may be invoked an arbitrary number of times (even 0).

    As an example, consider summing up the integer values of a list of chars. The initial value for the sum is 0. First, seqop transforms each input character to an Int and adds it to the sum (of the partition). Then, combop just needs to sum up the intermediate results of the partitions:

    List('a', 'b', 'c').aggregate(0)({ (sum, ch) => sum + ch.toInt }, { (p1, p2) => p1 + p2 })
    B

    the type of accumulated results

    z

    the initial value for the accumulated result of the partition - this will typically be the neutral element for the seqop operator (e.g. Nil for list concatenation or 0 for summation) and may be evaluated more than once

    seqop

    an operator used to accumulate results within a partition

    combop

    an associative operator used to combine results from different partitions

    Definition Classes
    TraversableOnceGenTraversableOnce
  10. def canEqual(that: Any): Boolean

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

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

    that

    The object with which this iterable collection should be compared

    returns

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

    Definition Classes
    IterableLikeEquals
  11. def collect[B](pf: PartialFunction[A, B]): Iterable[B]

    [use case] Builds a new collection by applying a partial function to all elements of this iterable collection on which the function is defined.

    [use case]

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

    B

    the element type of the returned collection.

    pf

    the partial function which filters and maps the iterable collection.

    returns

    a new iterable 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.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
    Full Signature

    def collect[B, That](pf: PartialFunction[B, B])(implicit bf: CanBuildFrom[IterableView[B, Coll], B, That]): That

  12. def collectFirst[B](pf: PartialFunction[B, B]): Option[B]

    Finds the first element of the traversable or iterator for which the given partial function is defined, and applies the partial function to it.

    Finds the first element of the traversable or iterator 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.

    Definition Classes
    TraversableOnce
    Example:
    1. Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)

  13. def companion: GenericCompanion[Iterable]

    The factory companion object that builds instances of class Iterable.

    The factory companion object that builds instances of class Iterable. (or its Iterable superclass where class Iterable is not a Seq.)

    Definition Classes
    IterableGenIterableTraversableGenTraversableGenericTraversableTemplate
  14. def copyToArray(xs: Array[A], start: Int, len: Int): Unit

    [use case] Copies the elements of this iterable collection to an array.

    [use case]

    Copies the elements of this iterable collection to an array. Fills the given array xs with at most len elements of this iterable collection, starting at position start. Copying will stop once either the end of the current iterable collection is reached, or the end of the target array is reached, or len elements have been copied.

    Note: will not terminate for infinite-sized collections.

    xs

    the array to fill.

    start

    the starting index.

    len

    the maximal number of elements to copy.

    Definition Classes
    IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
    Full Signature

    def copyToArray[B >: B](xs: Array[B], start: Int, len: Int): Unit

  15. def copyToArray(xs: Array[A]): Unit

    [use case] Copies the elements of this iterable collection to an array.

    [use case]

    Copies the elements of this iterable collection to an array. Fills the given array xs with values of this iterable collection. Copying will stop once either the end of the current iterable collection is reached, or the end of the target array is reached.

    Note: will not terminate for infinite-sized collections.

    xs

    the array to fill.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def copyToArray[B >: B](xs: Array[B]): Unit

  16. def copyToArray(xs: Array[A], start: Int): Unit

    [use case] Copies the elements of this iterable collection to an array.

    [use case]

    Copies the elements of this iterable collection to an array. Fills the given array xs with values of this iterable collection, beginning at index start. Copying will stop once either the end of the current iterable collection is reached, or the end of the target array is reached.

    Note: will not terminate for infinite-sized collections.

    xs

    the array to fill.

    start

    the starting index.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def copyToArray[B >: B](xs: Array[B], start: Int): Unit

  17. def copyToBuffer[B >: B](dest: Buffer[B]): Unit

    Copies all elements of this traversable or iterator to a buffer.

    Copies all elements of this traversable or iterator to a buffer.

    Note: will not terminate for infinite-sized collections.

    dest

    The buffer to which elements are copied.

    Definition Classes
    TraversableOnce
  18. def count(p: (B) ⇒ Boolean): Int

    Counts the number of elements in the traversable or iterator which satisfy a predicate.

    Counts the number of elements in the traversable or iterator which satisfy a predicate.

    p

    the predicate used to test elements.

    returns

    the number of elements satisfying the predicate p.

    Definition Classes
    TraversableOnceGenTraversableOnce
  19. def drop(n: Int): IterableView[B, Coll]

    Selects all elements except first n ones.

    Selects all elements except 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 iterable collection.

    returns

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

    Definition Classes
    IterableViewLikeTraversableViewLikeIterableLikeTraversableLikeGenTraversableLike
  20. def dropRight(n: Int): IterableView[B, Coll]

    Selects all elements except last n ones.

    Selects all elements except last n ones.

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

    n

    The number of elements to take

    returns

    a iterable collection consisting of all elements of this iterable collection except the last n ones, or else the empty iterable collection, if this iterable collection has less than n elements.

    Definition Classes
    IterableViewLikeIterableLike
  21. def dropWhile(p: (B) ⇒ Boolean): IterableView[B, Coll]

    Drops longest prefix of elements that satisfy a predicate.

    Drops longest prefix of elements that satisfy a predicate.

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

    returns

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

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
  22. def exists(p: (B) ⇒ Boolean): Boolean

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

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

    Note: may not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

    false if this iterable collection is empty, otherwise true if the given predicate p holds for some of the elements of this iterable collection, otherwise false

    Definition Classes
    IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
  23. def filter(p: (B) ⇒ Boolean): IterableView[B, Coll]

    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.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
  24. def filterNot(p: (B) ⇒ Boolean): IterableView[B, Coll]

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

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

    p

    the predicate used to test elements.

    returns

    a new collection consisting of all elements of this collection that do not satisfy the given predicate p. The order of the elements is preserved.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
  25. def find(p: (B) ⇒ Boolean): Option[B]

    Finds the first element of the iterable collection satisfying a predicate, if any.

    Finds the first element of the iterable 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 iterable collection that satisfies p, or None if none exists.

    Definition Classes
    IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
  26. def flatMap[B](f: (A) ⇒ GenTraversableOnce[B]): Iterable[B]

    [use case] Builds a new collection by applying a function to all elements of this iterable collection and using the elements of the resulting collections.

    [use case]

    Builds a new collection by applying a function to all elements of this iterable 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 iterable 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 => 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 iterable collection resulting from applying the given collection-valued function f to each element of this iterable collection and concatenating the results.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLikeFilterMonadic
    Full Signature

    def flatMap[B, That](f: (B) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[IterableView[B, Coll], B, That]): That

  27. def flatten[B]: Iterable[B]

    [use case] Converts this iterable collection of traversable collections into a iterable collection formed by the elements of these traversable collections.

    [use case]

    Converts this iterable collection of traversable collections into a iterable collection formed by the elements of these traversable collections.

    The resulting collection's type will be guided by the static type of iterable 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 traversable collection.

    returns

    a new iterable collection resulting from concatenating all element iterable collections.

    Definition Classes
    TraversableViewLikeGenericTraversableTemplate
    Full Signature

    def flatten[B](implicit asTraversable: (B) ⇒ GenTraversableOnce[B]): Mapped.Transformed[B]

  28. def fold[A1 >: B](z: A1)(op: (A1, A1) ⇒ A1): A1

    Folds the elements of this traversable or iterator using the specified associative binary operator.

    Folds the elements of this traversable or iterator using the specified associative binary operator.

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

    Note: will not terminate for infinite-sized collections.

    A1

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

    z

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

    op

    a binary operator that must be associative.

    returns

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

    Definition Classes
    TraversableOnceGenTraversableOnce
  29. def foldLeft[B](z: B)(op: (B, B) ⇒ B): B

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

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

    Note: will not terminate for infinite-sized collections.

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

    B

    the result type of the binary operator.

    z

    the start value.

    op

    the binary operator.

    returns

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

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

    where x1, ..., xn are the elements of this traversable or iterator. Returns z if this traversable or iterator is empty.

    Definition Classes
    TraversableOnceGenTraversableOnce
  30. def foldRight[B](z: B)(op: (B, B) ⇒ B): B

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

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

    Note: will not terminate for infinite-sized collections.

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

    B

    the result type of the binary operator.

    z

    the start value.

    op

    the binary operator.

    returns

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

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

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

    Definition Classes
    IterableLikeTraversableOnceGenTraversableOnce
  31. def forall(p: (B) ⇒ Boolean): Boolean

    Tests whether a predicate holds for all elements of this iterable collection.

    Tests whether a predicate holds for all elements of this iterable collection.

    Note: may not terminate for infinite-sized collections.

    p

    the predicate used to test elements.

    returns

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

    Definition Classes
    IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
  32. def force[B >: B, That](implicit bf: CanBuildFrom[Coll, B, That]): That
    Definition Classes
    TraversableViewLike
  33. def foreach(f: (A) ⇒ Unit): Unit

    [use case] Applies a function f to all elements of this iterable collection.

    [use case]

    Applies a function f to all elements of this iterable collection.

    f

    the function that is applied for its side-effect to every element. The result of function f is discarded.

    Definition Classes
    TransformedTransformedIterableLikeGenericTraversableTemplateTraversableLikeGenTraversableLikeTraversableOnceGenTraversableOnceFilterMonadic
    Full Signature

    def foreach[U](f: (B) ⇒ U): Unit

  34. def genericBuilder[B]: Builder[B, Iterable[B]]

    The generic builder that builds instances of Traversable at arbitrary element types.

    The generic builder that builds instances of Traversable at arbitrary element types.

    Definition Classes
    GenericTraversableTemplate
  35. def groupBy[K](f: (B) ⇒ K): immutable.Map[K, IterableView[B, Coll]]

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

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

    Note: this method is not re-implemented by views. This means when applied to a view it will always force the view and return a new collection.

    K

    the type of keys returned by the discriminator function.

    f

    the discriminator function.

    returns

    A map from keys to 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 collection of those elements x for which f(x) equals k.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
  36. def grouped(size: Int): Iterator[IterableView[B, Coll]]

    Partitions elements in fixed size iterable collections.

    Partitions elements in fixed size iterable collections.

    size

    the number of elements per group

    returns

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

    Definition Classes
    IterableViewLikeIterableLike
    See also

    scala.collection.Iterator, method grouped

  37. def hasDefiniteSize: Boolean

    Tests whether this traversable collection is known to have a finite size.

    Tests whether this traversable 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 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.

    returns

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

    Definition Classes
    TraversableLikeTraversableOnceGenTraversableOnce
  38. def head: B

    Selects the first element of this iterable collection.

    Selects the first element of this iterable collection.

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

    returns

    the first element of this iterable collection.

    Definition Classes
    IterableLikeTraversableLikeGenTraversableLike
    Exceptions thrown

    NoSuchElementException if the iterable collection is empty.

  39. def headOption: Option[B]

    Optionally selects the first element.

    Optionally selects the first element.

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

    returns

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

    Definition Classes
    TransformedTraversableLikeGenTraversableLike
  40. def init: IterableView[B, Coll]

    Selects all elements except the last.

    Selects all elements except the last.

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

    returns

    a collection consisting of all elements of this collection except the last one.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
    Exceptions thrown

    UnsupportedOperationException if the collection is empty.

  41. def inits: Iterator[IterableView[B, Coll]]

    Iterates over the inits of this collection.

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

    returns

    an iterator over all the inits of this collection

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

  42. def isEmpty: Boolean

    Tests whether this iterable collection is empty.

    Tests whether this iterable collection is empty.

    returns

    true if the iterable collection contain no elements, false otherwise.

    Definition Classes
    TransformedIterableLikeGenericTraversableTemplateTraversableLikeTraversableOnceGenTraversableOnce
  43. final def isTraversableAgain: Boolean

    Tests whether this traversable collection can be repeatedly traversed.

    Tests whether this traversable collection can be repeatedly traversed.

    returns

    true

    Definition Classes
    TraversableLikeGenTraversableLikeGenTraversableOnce
  44. def iterator: Iterator[B]

    Creates a new iterator over all elements contained in this iterable object.

    Creates a new iterator over all elements contained in this iterable object.

    returns

    the new iterator

    Definition Classes
    MappedTransformedIterableLikeGenIterableLike
  45. def last: B

    Selects the last element.

    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 collection.

    Definition Classes
    TransformedTraversableLikeGenTraversableLike
    Exceptions thrown

    NoSuchElementException If the collection is empty.

  46. def lastOption: Option[B]

    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 collection$ if it is nonempty, None if it is empty.

    Definition Classes
    TransformedTraversableLikeGenTraversableLike
  47. def map[B](f: (A) ⇒ B): Iterable[B]

    [use case] Builds a new collection by applying a function to all elements of this iterable collection.

    [use case]

    Builds a new collection by applying a function to all elements of this iterable collection.

    B

    the element type of the returned collection.

    f

    the function to apply to each element.

    returns

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

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLikeFilterMonadic
    Full Signature

    def map[B, That](f: (B) ⇒ B)(implicit bf: CanBuildFrom[IterableView[B, Coll], B, That]): That

  48. def max: A

    [use case] Finds the largest element.

    [use case]

    Finds the largest element.

    returns

    the largest element of this iterable collection.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def max[B >: B](implicit cmp: Ordering[B]): B

    Exceptions thrown

    UnsupportedOperationException if this iterable collection is empty.

  49. def maxBy[B](f: (A) ⇒ B): A

    [use case] Finds the first element which yields the largest value measured by function f.

    [use case]

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

    B

    The result type of the function f.

    f

    The measuring function.

    returns

    the first element of this iterable collection with the largest value measured by function f.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def maxBy[B](f: (B) ⇒ B)(implicit cmp: Ordering[B]): B

    Exceptions thrown

    UnsupportedOperationException if this iterable collection is empty.

  50. def min: A

    [use case] Finds the smallest element.

    [use case]

    Finds the smallest element.

    returns

    the smallest element of this iterable collection

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def min[B >: B](implicit cmp: Ordering[B]): B

    Exceptions thrown

    UnsupportedOperationException if this iterable collection is empty.

  51. def minBy[B](f: (A) ⇒ B): A

    [use case] Finds the first element which yields the smallest value measured by function f.

    [use case]

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

    B

    The result type of the function f.

    f

    The measuring function.

    returns

    the first element of this iterable collection with the smallest value measured by function f.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def minBy[B](f: (B) ⇒ B)(implicit cmp: Ordering[B]): B

    Exceptions thrown

    UnsupportedOperationException if this iterable collection is empty.

  52. def mkString(start: String, sep: String, end: String): String
    Definition Classes
    ViewMkString
  53. def mkString(sep: String): String
    Definition Classes
    ViewMkString
  54. def mkString: String
    Definition Classes
    ViewMkString
  55. def nonEmpty: Boolean

    Tests whether the traversable or iterator is not empty.

    Tests whether the traversable or iterator is not empty.

    returns

    true if the traversable or iterator contains at least one element, false otherwise.

    Definition Classes
    TraversableOnceGenTraversableOnce
  56. def par: ParIterable[B]

    Returns a parallel implementation of this collection.

    Returns a parallel implementation of this collection.

    For most collection types, this method creates a new parallel collection by copying all the elements. For these collection, par takes linear time. Mutable collections in this category do not produce a mutable parallel collection that has the same underlying dataset, so changes in one collection will not be reflected in the other one.

    Specific collections (e.g. ParArray or mutable.ParHashMap) override this default behaviour by creating a parallel collection which shares the same underlying dataset. For these collections, par takes constant or sublinear time.

    All parallel collections return a reference to themselves.

    returns

    a parallel implementation of this collection

    Definition Classes
    Parallelizable
  57. def partition(p: (B) ⇒ Boolean): (IterableView[B, Coll], IterableView[B, Coll])

    Partitions this collection in two collections according to a predicate.

    Partitions this collection in two collections according to a predicate.

    p

    the predicate on which to partition.

    returns

    a pair of collections: the first collection consists of all elements that satisfy the predicate p and the second collection consists of all elements that don't. The relative order of the elements in the resulting collections is the same as in the original collection.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
  58. def product: A

    [use case] Multiplies up the elements of this collection.

    [use case]

    Multiplies up the elements of this collection.

    returns

    the product of all elements in this iterable collection of numbers of type Int. Instead of Int, any other type T with an implicit Numeric[T] implementation can be used as element type of the iterable collection and as result type of product. Examples of such types are: Long, Float, Double, BigInt.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def product[B >: B](implicit num: Numeric[B]): B

  59. def reduce[A1 >: B](op: (A1, A1) ⇒ A1): A1

    Reduces the elements of this traversable or iterator using the specified associative binary operator.

    Reduces the elements of this traversable or iterator using the specified associative binary operator.

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

    A1

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

    op

    A binary operator that must be associative.

    returns

    The result of applying reduce operator op between all the elements if the traversable or iterator is nonempty.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Exceptions thrown

    UnsupportedOperationException if this traversable or iterator is empty.

  60. def reduceLeft[B >: B](op: (B, B) ⇒ B): B

    Applies a binary operator to all elements of this traversable or iterator, going left to right.

    Applies a binary operator to all elements of this traversable or iterator, going left to right.

    Note: will not terminate for infinite-sized collections.

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

    B

    the result type of the binary operator.

    op

    the binary operator.

    returns

    the result of inserting op between consecutive elements of this traversable or iterator, going left to right:

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

    where x1, ..., xn are the elements of this traversable or iterator.

    Definition Classes
    TraversableOnce
    Exceptions thrown

    UnsupportedOperationException if this traversable or iterator is empty.

  61. def reduceLeftOption[B >: B](op: (B, B) ⇒ B): Option[B]

    Optionally applies a binary operator to all elements of this traversable or iterator, going left to right.

    Optionally applies a binary operator to all elements of this traversable or iterator, going left to right.

    Note: will not terminate for infinite-sized collections.

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

    B

    the result type of the binary operator.

    op

    the binary operator.

    returns

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

    Definition Classes
    TraversableOnceGenTraversableOnce
  62. def reduceOption[A1 >: B](op: (A1, A1) ⇒ A1): Option[A1]

    Reduces the elements of this traversable or iterator, if any, using the specified associative binary operator.

    Reduces the elements of this traversable or iterator, if any, using the specified associative binary operator.

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

    A1

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

    op

    A binary operator that must be associative.

    returns

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

    Definition Classes
    TraversableOnceGenTraversableOnce
  63. def reduceRight[B >: B](op: (B, B) ⇒ B): B

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

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

    Note: will not terminate for infinite-sized collections.

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

    B

    the result type of the binary operator.

    op

    the binary operator.

    returns

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

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

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

    Definition Classes
    IterableLikeTraversableOnceGenTraversableOnce
    Exceptions thrown

    UnsupportedOperationException if this iterable collection is empty.

  64. def reduceRightOption[B >: B](op: (B, B) ⇒ B): Option[B]

    Optionally applies a binary operator to all elements of this traversable or iterator, going right to left.

    Optionally applies a binary operator to all elements of this traversable or iterator, going right to left.

    Note: will not terminate for infinite-sized collections.

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

    B

    the result type of the binary operator.

    op

    the binary operator.

    returns

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

    Definition Classes
    TraversableOnceGenTraversableOnce
  65. def repr: IterableView[B, Coll]

    The collection of type traversable collection underlying this TraversableLike object.

    The collection of type traversable collection underlying this TraversableLike object. By default this is implemented as the TraversableLike object itself, but this can be overridden.

    Definition Classes
    TraversableLikeGenTraversableLike
  66. def sameElements(that: GenIterable[A]): Boolean

    [use case] Checks if the other iterable collection contains the same elements in the same order as this iterable collection.

    [use case]

    Checks if the other iterable collection contains the same elements in the same order as this iterable collection.

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

    Note: will not terminate for infinite-sized collections.

    that

    the collection to compare with.

    returns

    true, if both collections contain the same elements in the same order, false otherwise.

    Definition Classes
    IterableLikeGenIterableLike
    Full Signature

    def sameElements[B >: B](that: GenIterable[B]): Boolean

  67. def scan[B >: B, That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[IterableView[B, Coll], B, That]): That

    Computes a prefix scan of the elements of the collection.

    Computes a prefix scan of the elements of the collection.

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

    B

    element type of the resulting collection

    That

    type of the resulting collection

    z

    neutral element for the operator op

    op

    the associative operator for the scan

    cbf

    combiner factory which provides a combiner

    returns

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

    Definition Classes
    TraversableLikeGenTraversableLike
  68. def scanLeft[B, That](z: B)(op: (B, B) ⇒ B)(implicit bf: CanBuildFrom[IterableView[B, Coll], B, That]): That

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

    Produces a collection containing cumulative results of applying the operator 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.

    B

    the type of the elements in the resulting collection

    That

    the actual type of the resulting collection

    z

    the initial value

    op

    the binary operator applied to the intermediate result and the element

    bf

    an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and the new element type B.

    returns

    collection with intermediate results

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
  69. def scanRight[B, That](z: B)(op: (B, B) ⇒ B)(implicit bf: CanBuildFrom[IterableView[B, Coll], B, That]): That

    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.

    Example:

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

    the type of the elements in the resulting collection

    That

    the actual type of the resulting collection

    z

    the initial value

    op

    the binary operator applied to the intermediate result and the element

    bf

    an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and the new element type B.

    returns

    collection with intermediate results

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
    Annotations
    @migration
    Migration

    (Changed in version 2.9.0) The behavior of scanRight has changed. The previous behavior can be reproduced with scanRight.reverse.

  70. def seq: Iterable[B]

    A version of this collection with all of the operations implemented sequentially (i.e., in a single-threaded manner).

    A version of this collection with all of the operations implemented sequentially (i.e., in a single-threaded manner).

    This method returns a reference to this collection. In parallel collections, it is redefined to return a sequential implementation of this collection. In both cases, it has O(1) complexity.

    returns

    a sequential view of the collection.

    Definition Classes
    IterableGenIterableTraversableGenTraversableParallelizableTraversableOnceGenTraversableOnce
  71. def size: Int

    The size of this traversable or iterator.

    The size of this traversable or iterator.

    Note: will not terminate for infinite-sized collections.

    returns

    the number of elements in this traversable or iterator.

    Definition Classes
    TraversableOnceGenTraversableOnce
  72. def slice(from: Int, until: Int): IterableView[B, Coll]

    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.

    returns

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

    Definition Classes
    IterableLikeTraversableLikeGenTraversableLike
  73. def sliding(size: Int): Iterator[IterableView[B, Coll]]

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

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

    size

    the number of elements per group

    returns

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

    Definition Classes
    IterableViewLikeIterableLike
    See also

    scala.collection.Iterator, method sliding

  74. def sliding(size: Int, step: Int): Iterator[IterableView[B, Coll]]

    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.)

    size

    the number of elements per group

    step

    the distance between the first elements of successive groups

    returns

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

    Definition Classes
    IterableViewLikeIterableLike
    See also

    scala.collection.Iterator, method sliding

  75. def span(p: (B) ⇒ Boolean): (IterableView[B, Coll], IterableView[B, Coll])

    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 predicate p does not cause any side-effects.

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

    returns

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

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
  76. def splitAt(n: Int): (IterableView[B, Coll], IterableView[B, Coll])

    Splits this collection into two at a given position.

    Splits this collection into two 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.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
  77. def stringPrefix: String

    Defines the prefix of this object's toString representation.

    Defines the prefix of this object's toString representation.

    returns

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

    Definition Classes
    IterableViewLikeTraversableViewLikeTraversableLikeGenTraversableLike
  78. def sum: A

    [use case] Sums up the elements of this collection.

    [use case]

    Sums up the elements of this collection.

    returns

    the sum of all elements in this iterable collection of numbers of type Int. Instead of Int, any other type T with an implicit Numeric[T] implementation can be used as element type of the iterable collection and as result type of sum. Examples of such types are: Long, Float, Double, BigInt.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def sum[B >: B](implicit num: Numeric[B]): B

  79. def tail: IterableView[B, Coll]

    Selects all elements except the first.

    Selects all elements except the first.

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

    returns

    a collection consisting of all elements of this collection except the first one.

    Definition Classes
    TraversableViewLikeTraversableLikeGenTraversableLike
    Exceptions thrown

    java.lang.UnsupportedOperationException if the collection is empty.

  80. def tails: Iterator[IterableView[B, Coll]]

    Iterates over the tails of this collection.

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

    returns

    an iterator over all the tails of this collection

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

  81. def take(n: Int): IterableView[B, Coll]

    Selects first n elements.

    Selects 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 iterable collection.

    returns

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

    Definition Classes
    IterableViewLikeTraversableViewLikeIterableLikeTraversableLikeGenTraversableLike
  82. def takeRight(n: Int): IterableView[B, Coll]

    Selects last n elements.

    Selects last n elements.

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

    n

    the number of elements to take

    returns

    a iterable collection consisting only of the last n elements of this iterable collection, or else the whole iterable collection, if it has less than n elements.

    Definition Classes
    IterableViewLikeIterableLike
  83. def takeWhile(p: (B) ⇒ Boolean): IterableView[B, Coll]

    Takes longest prefix of elements that satisfy a predicate.

    Takes longest prefix of elements that satisfy a predicate.

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

    returns

    the longest prefix of this iterable collection whose elements all satisfy the predicate p.

    Definition Classes
    IterableLikeTraversableLikeGenTraversableLike
  84. def to[Col[_]]: Col[A]

    [use case] Converts this iterable collection into another by copying all elements.

    [use case]

    Converts this iterable collection into another by copying all elements.

    Note: will not terminate for infinite-sized collections.

    Col

    The collection type to build.

    returns

    a new collection containing all elements of this iterable collection.

    Definition Classes
    TraversableLikeTraversableOnceGenTraversableOnce
    Full Signature

    def to[Col[_]](implicit cbf: CanBuildFrom[Nothing, B, Col[B]]): Col[B]

  85. def toArray: Array[A]

    [use case] Converts this iterable collection to an array.

    [use case]

    Converts this iterable collection to an array.

    Note: will not terminate for infinite-sized collections.

    returns

    an array containing all elements of this iterable collection. An ClassTag must be available for the element type of this iterable collection.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def toArray[B >: B](implicit arg0: ClassTag[B]): Array[B]

  86. def toBuffer[B >: B]: Buffer[B]

    Uses the contents of this traversable or iterator to create a new mutable buffer.

    Uses the contents of this traversable or iterator to create a new mutable buffer.

    Note: will not terminate for infinite-sized collections.

    returns

    a buffer containing all elements of this traversable or iterator.

    Definition Classes
    TraversableOnceGenTraversableOnce
  87. def toIndexedSeq: immutable.IndexedSeq[B]

    Converts this traversable or iterator to an indexed sequence.

    Converts this traversable or iterator to an indexed sequence.

    Note: will not terminate for infinite-sized collections.

    returns

    an indexed sequence containing all elements of this traversable or iterator.

    Definition Classes
    TraversableOnceGenTraversableOnce
  88. def toIterable: Iterable[B]

    Returns this iterable collection as an iterable collection.

    Returns this iterable collection as an iterable collection.

    A new collection will not be built; lazy collections will stay lazy.

    Note: will not terminate for infinite-sized collections.

    returns

    an Iterable containing all elements of this iterable collection.

    Definition Classes
    IterableLikeTraversableOnceGenTraversableOnce
  89. def toIterator: Iterator[B]

    Returns an Iterator over the elements in this iterable collection.

    Returns an Iterator over the elements in this iterable collection. Produces the same result as iterator.

    Note: will not terminate for infinite-sized collections.

    returns

    an Iterator containing all elements of this iterable collection.

    Definition Classes
    IterableLikeTraversableLikeGenTraversableOnce
    Annotations
    @deprecatedOverriding( message = ... , since = "2.11.0" )
  90. def toList: List[B]

    Converts this traversable or iterator to a list.

    Converts this traversable or iterator to a list.

    Note: will not terminate for infinite-sized collections.

    returns

    a list containing all elements of this traversable or iterator.

    Definition Classes
    TraversableOnceGenTraversableOnce
  91. def toMap[T, U]: Map[T, U]

    [use case] Converts this iterable collection to a map.

    [use case]

    Converts this iterable collection to a map. This method is unavailable unless the elements are members of Tuple2, each ((T, U)) becoming a key-value pair in the map. Duplicate keys will be overwritten by later keys: if this is an unordered collection, which key is in the resulting map is undefined.

    Note: will not terminate for infinite-sized collections.

    returns

    a map of type immutable.Map[T, U] containing all key/value pairs of type (T, U) of this iterable collection.

    Definition Classes
    TraversableOnceGenTraversableOnce
    Full Signature

    def toMap[T, U](implicit ev: <:<[B, (T, U)]): immutable.Map[T, U]

  92. def toParArray: ParArray[T]
    Implicit
    This member is added by an implicit conversion from Mapped[B] to CollectionsHaveToParArray[Mapped[B], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (Mapped[B]) ⇒ GenTraversableOnce[T] is in scope.
    Definition Classes
    CollectionsHaveToParArray
  93. def toSeq: Seq[B]

    Converts this traversable or iterator to a sequence.

    Converts this traversable or iterator to a sequence. As with toIterable, it's lazy in this default implementation, as this TraversableOnce may be lazy and unevaluated.

    Note: will not terminate for infinite-sized collections.

    returns

    a sequence containing all elements of this traversable or iterator.

    Definition Classes
    TraversableOnceGenTraversableOnce
  94. def toSet[B >: B]: immutable.Set[B]

    Converts this traversable or iterator to a set.

    Converts this traversable or iterator to a set.

    Note: will not terminate for infinite-sized collections.

    returns

    a set containing all elements of this traversable or iterator.

    Definition Classes
    TraversableOnceGenTraversableOnce
  95. def toStream: immutable.Stream[B]

    Converts this iterable collection to a stream.

    Converts this iterable collection to a stream.

    returns

    a stream containing all elements of this iterable collection.

    Definition Classes
    IterableLikeTraversableLikeGenTraversableOnce
  96. def toString(): String

    Converts this iterable collection to a string.

    Converts this iterable collection to a string.

    returns

    a string representation of this collection. By default this string consists of the stringPrefix of this iterable collection, followed by all elements separated by commas and enclosed in parentheses.

    Definition Classes
    TransformedTransformedTraversableViewLikeTraversableLike → AnyRef → Any
  97. def toTraversable: Traversable[B]

    Converts this traversable collection to an unspecified Traversable.

    Converts this traversable collection to an unspecified Traversable. Will return the same collection if this instance is already Traversable.

    Note: will not terminate for infinite-sized collections.

    returns

    a Traversable containing all elements of this traversable collection.

    Definition Classes
    TraversableLikeTraversableOnceGenTraversableOnce
    Annotations
    @deprecatedOverriding( message = ... , since = "2.11.0" )
  98. def toVector: Vector[B]

    Converts this traversable or iterator to a Vector.

    Converts this traversable or iterator to a Vector.

    Note: will not terminate for infinite-sized collections.

    returns

    a vector containing all elements of this traversable or iterator.

    Definition Classes
    TraversableOnceGenTraversableOnce
  99. def transpose[B](implicit asTraversable: (B) ⇒ GenTraversableOnce[B]): Iterable[Iterable[B]]

    Transposes this collection of traversable collections into a collection of collections.

    Transposes this collection of traversable collections into a collection of collections.

    The resulting collection's type will be guided by the static type of collection. 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))
    B

    the type of the elements of each traversable collection.

    asTraversable

    an implicit conversion which asserts that the element type of this collection is a Traversable.

    returns

    a two-dimensional collection of collections which has as nth row the nth column of this collection.

    Definition Classes
    GenericTraversableTemplate
    Annotations
    @migration
    Migration

    (Changed in version 2.9.0) transpose throws an IllegalArgumentException if collections are not uniformly sized.

    Exceptions thrown

    IllegalArgumentException if all collections in this collection are not of the same size.

  100. lazy val underlying: Coll
    Definition Classes
    TransformedTraversableViewLike
  101. def unzip[A1, A2](implicit asPair: (B) ⇒ (A1, A2)): (Mapped.Transformed[A1], Mapped.Transformed[A2])

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

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

    val xs = Traversable(
               (1, "one"),
               (2, "two"),
               (3, "three")).unzip
    // xs == (Traversable(1, 2, 3),
    //        Traversable(one, two, three))
    A1

    the type of the first half of the element pairs

    A2

    the type of the second half of the element pairs

    asPair

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

    returns

    a pair of collections, containing the first, respectively second half of each element pair of this collection.

    Definition Classes
    TraversableViewLikeGenericTraversableTemplate
  102. def unzip3[A1, A2, A3](implicit asTriple: (B) ⇒ (A1, A2, A3)): (Mapped.Transformed[A1], Mapped.Transformed[A2], Mapped.Transformed[A3])

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

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

    val xs = Traversable(
               (1, "one", '1'),
               (2, "two", '2'),
               (3, "three", '3')).unzip3
    // xs == (Traversable(1, 2, 3),
    //        Traversable(one, two, three),
    //        Traversable(1, 2, 3))
    A1

    the type of the first member of the element triples

    A2

    the type of the second member of the element triples

    A3

    the type of the third member of the element triples

    asTriple

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

    returns

    a triple of collections, containing the first, second, respectively third member of each element triple of this collection.

    Definition Classes
    TraversableViewLikeGenericTraversableTemplate
  103. def view(from: Int, until: Int): IterableView[B, IterableView[B, Coll]]

    Creates a non-strict view of a slice of this iterable collection.

    Creates a non-strict view of a slice of this iterable collection.

    Note: the difference between view and slice is that view produces a view of the current iterable collection, whereas slice produces a new iterable collection.

    Note: view(from, to) is equivalent to view.slice(from, to)

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

    from

    the index of the first element of the view

    until

    the index of the element following the view

    returns

    a non-strict view of a slice of this iterable collection, starting at index from and extending up to (but not including) index until.

    Definition Classes
    IterableLikeTraversableLike
  104. def view: IterableView[B, IterableView[B, Coll]]

    Creates a non-strict view of this iterable collection.

    Creates a non-strict view of this iterable collection.

    returns

    a non-strict view of this iterable collection.

    Definition Classes
    IterableLikeTraversableLike
  105. def viewToString: String
    Definition Classes
    TraversableViewLike
  106. def withFilter(p: (B) ⇒ Boolean): IterableView[B, Coll]

    Creates a non-strict filter of this collection.

    Creates a non-strict filter of this collection.

    Note: the difference between c filter p and c withFilter p is that the former creates a new collection, whereas the latter only restricts the domain of subsequent map, flatMap, foreach, and withFilter operations.

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

    p

    the predicate used to test elements.

    returns

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

    Definition Classes
    TraversableViewLikeTraversableLikeFilterMonadic
  107. def zip[B](that: GenIterable[B]): Iterable[(A, B)]

    [use case] Returns a iterable collection formed from this iterable collection and another iterable collection by combining corresponding elements in pairs.

    [use case]

    Returns a iterable collection formed from this iterable collection 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.

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

    B

    the type of the second half of the returned pairs

    that

    The iterable providing the second half of each result pair

    returns

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

    Definition Classes
    IterableViewLikeIterableLikeGenIterableLike
    Full Signature

    def zip[A1 >: B, B, That](that: GenIterable[B])(implicit bf: CanBuildFrom[IterableView[B, Coll], (A1, B), That]): That

  108. def zipAll[B](that: Iterable[B], thisElem: A, thatElem: B): Iterable[(A, B)]

    [use case] Returns a iterable collection formed from this iterable collection and another iterable collection by combining corresponding elements in pairs.

    [use case]

    Returns a iterable collection formed from this iterable collection 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.

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

    B

    the type of the second half of the returned pairs

    that

    The iterable providing the second half of each result pair

    thisElem

    the element to be used to fill up the result if this iterable collection is shorter than that.

    thatElem

    the element to be used to fill up the result if that is shorter than this iterable collection.

    returns

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

    Definition Classes
    IterableViewLikeIterableLikeGenIterableLike
    Full Signature

    def zipAll[B, A1 >: B, That](that: GenIterable[B], thisElem: A1, thatElem: B)(implicit bf: CanBuildFrom[IterableView[B, Coll], (A1, B), That]): That

  109. def zipWithIndex: Iterable[(A, Int)]

    [use case] Zips this iterable collection with its indices.

    [use case]

    Zips this iterable collection with its indices.

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

    returns

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

    Definition Classes
    IterableViewLikeIterableLikeGenIterableLike
    Full Signature

    def zipWithIndex[A1 >: B, That](implicit bf: CanBuildFrom[IterableView[B, Coll], (A1, Int), That]): That

    Example:
    1. List("a", "b", "c").zipWithIndex = List(("a", 0), ("b", 1), ("c", 2))

Shadowed Implicit Value Members

  1. def filter(p: (B) ⇒ Boolean): TraversableOnce[B]
    Implicit
    This member is added by an implicit conversion from Mapped[B] to MonadOps[B] performed by method MonadOps in scala.collection.TraversableOnce.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (mapped: MonadOps[B]).filter(p)
    Definition Classes
    MonadOps
  2. def flatMap[B](f: (B) ⇒ GenTraversableOnce[B]): TraversableOnce[B]
    Implicit
    This member is added by an implicit conversion from Mapped[B] to MonadOps[B] performed by method MonadOps in scala.collection.TraversableOnce.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (mapped: MonadOps[B]).flatMap(f)
    Definition Classes
    MonadOps
  3. def map[B](f: (B) ⇒ B): TraversableOnce[B]
    Implicit
    This member is added by an implicit conversion from Mapped[B] to MonadOps[B] performed by method MonadOps in scala.collection.TraversableOnce.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (mapped: MonadOps[B]).map(f)
    Definition Classes
    MonadOps
  4. def withFilter(p: (B) ⇒ Boolean): Iterator[B]
    Implicit
    This member is added by an implicit conversion from Mapped[B] to MonadOps[B] performed by method MonadOps in scala.collection.TraversableOnce.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (mapped: MonadOps[B]).withFilter(p)
    Definition Classes
    MonadOps