Traversable

Companion object Traversable

trait Traversable[+A] extends collection.Traversable[A] with GenericTraversableTemplate[A, Traversable] with TraversableLike[A, Traversable[A]] with Immutable

A trait for traversable collections that are guaranteed immutable.

This is a base trait of all kinds of immutable Scala collections. It implements the behavior common to all collections, in terms of a method foreach with signature:

def foreach[U](f: Elem => U): Unit

Collection classes mixing in this trait provide a concrete foreach method which traverses all the elements contained in the collection, applying a given function to each. They also need to provide a method newBuilder which creates a builder for collections of the same kind.

A traversable class might or might not have two properties: strictness and orderedness. Neither is represented as a type.

The instances of a strict collection class have all their elements computed before they can be used as values. By contrast, instances of a non-strict collection class may defer computation of some of their elements until after the instance is available as a value. A typical example of a non-strict collection class is a scala.collection.immutable.Stream. A more general class of examples are TraversableViews.

If a collection is an instance of an ordered collection class, traversing its elements with foreach will always visit elements in the same order, even for different runs of the program. If the class is not ordered, foreach can visit elements in different orders for different runs (but it will keep the same order in the same run).'

A typical example of a collection class which is not ordered is a HashMap of objects. The traversal order for hash maps will depend on the hash codes of its elements, and these hash codes might differ from one run to the next. By contrast, a LinkedHashMap is ordered because its foreach method visits elements in the order they were inserted into the HashMap.

Source: Traversable.scala

Linear Supertypes

Immutable, collection.Traversable[A], GenTraversable[A], GenericTraversableTemplate[A, Traversable], TraversableLike[A, Traversable[A]], GenTraversableLike[A, Traversable[A]], Parallelizable[A, ParIterable[A]], TraversableOnce[A], GenTraversableOnce[A], FilterMonadic[A, Traversable[A]], HasNewBuilder[A, scala.collection.immutable.Traversable[A] @scala.annotation.unchecked.uncheckedVariance], AnyRef, Any

Known Subclasses

ValueSet, ::, AbstractMap, BitSet, BitSet1, BitSet2, BitSetN, DefaultMap, HashMap, HashMap1, HashTrieMap, HashSet, HashTrieSet, IndexedSeq, Impl, IntMap, Iterable, LinearSeq, List, ListMap, Node, ListSet, Node, LongMap, Map, Map1, Map2, Map3, Map4, WithDefault, ImmutableDefaultKeySet, Nil, NumericRange, Exclusive, Inclusive, Queue, Range, Inclusive, Seq, Set, Set1, Set2, Set3, Set4, SortedMap, DefaultKeySortedSet, SortedSet, Stream, Cons, Empty, TreeMap, TreeSet, Vector, WrappedString, MapProxy, SetProxy, Stack

Ordering

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By Inheritance

Inherited

Traversable
Immutable
Traversable
GenTraversable
GenericTraversableTemplate
TraversableLike
GenTraversableLike
Parallelizable
TraversableOnce
GenTraversableOnce
FilterMonadic
HasNewBuilder
AnyRef
Any

Implicitly

by CollectionsHaveToParArray
by MonadOps
by any2stringadd
by StringFormat
by Ensuring
by ArrowAssoc
by alternateImplicit

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Visibility

Public
All

Type Members

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
type Self = Traversable[A]
The type implementing this traversable
The type implementing this traversable

Attributes
protected[this]
Definition Classes
TraversableLike

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

Definition Classes
AnyRef → Any
def +(other: String): String

Implicit
This member is added by an implicit conversion from Traversable[A] to any2stringadd[Traversable[A]] performed by method any2stringadd in scala.Predef.
Definition Classes
any2stringadd
def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Traversable[A], B, That]): That
Returns a new traversable collection containing the elements from the left hand operand followed by the elements from the right hand operand.
Returns a new traversable collection containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the traversable 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.
that
the traversable to append.
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 traversable collection followed by all elements of that.

Definition Classes
TraversableLike → GenTraversableLike
def ++:[B >: A, That](that: collection.Traversable[B])(implicit bf: CanBuildFrom[Traversable[A], 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.
that
the traversable to append.
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 traversable collection followed by all elements of that.

Definition Classes
TraversableLike
def ++:[B](that: TraversableOnce[B]): Traversable[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 collection which contains all elements of this collection followed by all elements of that.

Definition Classes
TraversableLike
Full Signature
def ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Traversable[A], B, That]): That
def ->[B](y: B): (Traversable[A], B)

Implicit
This member is added by an implicit conversion from Traversable[A] to ArrowAssoc[Traversable[A]] performed by method ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc
Annotations
@inline()
def /:[B](z: B)(op: (B, A) ⇒ 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, ..., x_n are the elements of this traversable or iterator.
Definition Classes
TraversableOnce → GenTraversableOnce
def :\[B](z: B)(op: (A, 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, ..., x_n are the elements of this traversable or iterator.
Definition Classes
TraversableOnce → GenTraversableOnce
final def ==(arg0: Any): Boolean
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
returns
true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
AnyRef → Any
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
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
def addString(b: StringBuilder, start: String, sep: String, end: String): StringBuilder
Appends all elements of this traversable or iterator to a string builder using start, end, and separator strings.
Appends all elements of this traversable or iterator to a string builder using start, end, and separator strings. The written text begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this traversable or iterator are 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 , "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.

Definition Classes
TraversableOnce
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.
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
TraversableOnce → GenTraversableOnce
final def asInstanceOf[T0]: T0
Cast the receiver object to be of type T0.
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.
returns
the receiver object.

Definition Classes
Any
Exceptions thrown
ClassCastException if the receiver object is not an instance of the erasure of type T0.
def clone(): AnyRef
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the clone method is platform dependent.
returns
a copy of the receiver object.

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@native() @throws( ... )
Note
not specified by SLS as a member of AnyRef
def collect[B](pf: PartialFunction[A, B]): Traversable[B]
[use case] Builds a new collection by applying a partial function to all elements of this collection on which the function is defined.
[use case]
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.

Definition Classes
TraversableLike → GenTraversableLike
Full Signature
def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Traversable[A], B, That]): That
def collectFirst[B](pf: PartialFunction[A, 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)
def companion: GenericCompanion[Traversable]
The factory companion object that builds instances of class Traversable.
The factory companion object that builds instances of class Traversable. (or its Iterable superclass where class Traversable is not a Seq.)

Definition Classes
Traversable → Traversable → GenTraversable → GenericTraversableTemplate
def copyToArray(xs: Array[A], start: Int, len: Int): Unit
[use case] Copies the elements of this collection to an array.
[use case]
Copies the elements of this collection to an array. Fills the given array xs with at most len elements of this collection, starting at position start. Copying will stop once either the end of the current 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
TraversableLike → TraversableOnce → GenTraversableOnce
Full Signature
def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Unit
def copyToArray(xs: Array[A]): Unit
[use case] Copies the elements of this collection to an array.
[use case]
Copies the elements of this collection to an array. Fills the given array xs with values of this collection. Copying will stop once either the end of the current 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
TraversableOnce → GenTraversableOnce
Full Signature
def copyToArray[B >: A](xs: Array[B]): Unit
def copyToArray(xs: Array[A], start: Int): Unit
[use case] Copies the elements of this collection to an array.
[use case]
Copies the elements of this collection to an array. Fills the given array xs with values of this collection, beginning at index start. Copying will stop once either the end of the current 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
TraversableOnce → GenTraversableOnce
Full Signature
def copyToArray[B >: A](xs: Array[B], start: Int): Unit
def copyToBuffer[B >: A](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
def count(p: (A) ⇒ 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
TraversableOnce → GenTraversableOnce
def drop(n: Int): Traversable[A]
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 traversable collection.
returns
a traversable collection consisting of all elements of this traversable collection except the first n ones, or else the empty traversable collection, if this traversable collection has less than n elements.

Definition Classes
TraversableLike → GenTraversableLike
def dropWhile(p: (A) ⇒ Boolean): Traversable[A]
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 traversable collection whose first element does not satisfy the predicate p.

Definition Classes
TraversableLike → GenTraversableLike
def ensuring(cond: (Traversable[A]) ⇒ Boolean, msg: ⇒ Any): Traversable[A]

Implicit
This member is added by an implicit conversion from Traversable[A] to Ensuring[Traversable[A]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def ensuring(cond: (Traversable[A]) ⇒ Boolean): Traversable[A]

Implicit
This member is added by an implicit conversion from Traversable[A] to Ensuring[Traversable[A]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def ensuring(cond: Boolean, msg: ⇒ Any): Traversable[A]

Implicit
This member is added by an implicit conversion from Traversable[A] to Ensuring[Traversable[A]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def ensuring(cond: Boolean): Traversable[A]

Implicit
This member is added by an implicit conversion from Traversable[A] to Ensuring[Traversable[A]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
final def eq(arg0: AnyRef): Boolean
Tests whether the argument (that) is a reference to the receiver object (this).
Tests whether the argument (that) is a reference to the receiver object (this).
The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:
- It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
- For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
- null.eq(null) returns true.
When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
returns
true if the argument is a reference to the receiver object; false otherwise.

Definition Classes
AnyRef
def equals(arg0: Any): Boolean
The equality method for reference types.
The equality method for reference types. Default implementation delegates to eq.
See also equals in scala.Any.
returns
true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
AnyRef → Any
def exists(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for at least one element of this traversable collection.
Tests whether a predicate holds for at least one element of this traversable collection.
Note: may not terminate for infinite-sized collections.
p
the predicate used to test elements.
returns
false if this traversable collection is empty, otherwise true if the given predicate p holds for some of the elements of this traversable collection, otherwise false

Definition Classes
TraversableLike → TraversableOnce → GenTraversableOnce
def filter(p: (A) ⇒ Boolean): Traversable[A]
Selects all elements of this traversable collection which satisfy a predicate.
Selects all elements of this traversable collection which satisfy a predicate.
p
the predicate used to test elements.
returns
a new traversable collection consisting of all elements of this traversable collection that satisfy the given predicate p. The order of the elements is preserved.

Definition Classes
TraversableLike → GenTraversableLike
def filterNot(p: (A) ⇒ Boolean): Traversable[A]
Selects all elements of this traversable collection which do not satisfy a predicate.
Selects all elements of this traversable collection which do not satisfy a predicate.
p
the predicate used to test elements.
returns
a new traversable collection consisting of all elements of this traversable collection that do not satisfy the given predicate p. The order of the elements is preserved.

Definition Classes
TraversableLike → GenTraversableLike
def finalize(): Unit
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
Note
not specified by SLS as a member of AnyRef
def find(p: (A) ⇒ Boolean): Option[A]
Finds the first element of the traversable collection satisfying a predicate, if any.
Finds the first element of the traversable 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 traversable collection that satisfies p, or None if none exists.

Definition Classes
TraversableLike → TraversableOnce → GenTraversableOnce
def flatMap[B](f: (A) ⇒ GenTraversableOnce[B]): Traversable[B]
[use case] Builds a new collection by applying a function to all elements of this collection and using the elements of the resulting collections.
[use case]
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 => 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.

Definition Classes
TraversableLike → GenTraversableLike → FilterMonadic
Full Signature
def flatMap[B, That](f: (A) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[Traversable[A], B, That]): That
def flatten[B]: Traversable[B]
[use case] Converts this collection of traversable collections into a collection formed by the elements of these traversable collections.
[use case]
Converts this collection of traversable collections into a collection formed by the elements of these traversable 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(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 collection resulting from concatenating all element collections.

Definition Classes
GenericTraversableTemplate
Full Signature
def flatten[B](implicit asTraversable: (A) ⇒ GenTraversableOnce[B]): Traversable[B]
def fold[A1 >: A](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
TraversableOnce → GenTraversableOnce
def foldLeft[B](z: B)(op: (B, A) ⇒ 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, ..., x_n are the elements of this traversable or iterator. Returns z if this traversable or iterator is empty.
Definition Classes
TraversableOnce → GenTraversableOnce
def foldRight[B](z: B)(op: (A, 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: 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 right to left with the start value z on the right:
```
op(x_1, op(x_2, ... op(x_n, z)...))
```
where x₁, ..., x_n are the elements of this traversable or iterator. Returns z if this traversable or iterator is empty.
Definition Classes
TraversableOnce → GenTraversableOnce
def forall(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for all elements of this traversable collection.
Tests whether a predicate holds for all elements of this traversable collection.
Note: may not terminate for infinite-sized collections.
p
the predicate used to test elements.
returns
true if this traversable collection is empty or the given predicate p holds for all elements of this traversable collection, otherwise false.

Definition Classes
TraversableLike → TraversableOnce → GenTraversableOnce
abstract def foreach(f: (A) ⇒ Unit): Unit
[use case]
[use case]
f
the function that is applied for its side-effect to every element. The result of function f is discarded.

Definition Classes
GenericTraversableTemplate
Full Signature
abstract def foreach[U](f: (A) ⇒ U): Unit
def formatted(fmtstr: String): String
Returns string formatted according to given format string.
Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).

Implicit
This member is added by an implicit conversion from Traversable[A] to StringFormat[Traversable[A]] performed by method StringFormat in scala.Predef.
Definition Classes
StringFormat
Annotations
@inline()
def genericBuilder[B]: Builder[B, Traversable[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
final def getClass(): Class[_]
Returns the runtime class representation of the object.
Returns the runtime class representation of the object.
returns
a class object corresponding to the runtime type of the receiver.

Definition Classes
AnyRef → Any
Annotations
@native()
def groupBy[K](f: (A) ⇒ K): Map[K, Traversable[A]]
Partitions this traversable collection into a map of traversable collections according to some discriminator function.
Partitions this traversable collection into a map of traversable 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 traversable collection.
K
the type of keys returned by the discriminator function.
f
the discriminator function.
returns
A map from keys to traversable 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 traversable collection of those elements x for which f(x) equals k.
Definition Classes
TraversableLike → GenTraversableLike
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
TraversableLike → TraversableOnce → GenTraversableOnce
def hashCode(): Int
The hashCode method for reference types.
The hashCode method for reference types. See hashCode in scala.Any.
returns
the hash code value for this object.

Definition Classes
AnyRef → Any
Annotations
@native()
def head: A
Selects the first element of this traversable collection.
Selects the first element of this traversable collection.
Note: might return different results for different runs, unless the underlying collection type is ordered.
returns
the first element of this traversable collection.

Definition Classes
TraversableLike → GenTraversableLike
Exceptions thrown
NoSuchElementException if the traversable collection is empty.
def headOption: Option[A]
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 traversable collection if it is nonempty, None if it is empty.

Definition Classes
TraversableLike → GenTraversableLike
def init: Traversable[A]
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 traversable collection consisting of all elements of this traversable collection except the last one.

Definition Classes
TraversableLike → GenTraversableLike
Exceptions thrown
UnsupportedOperationException if the traversable collection is empty.
def inits: Iterator[Traversable[A]]
Iterates over the inits of this traversable collection.
Iterates over the inits of this traversable collection. The first value will be this traversable collection and the final one will be an empty traversable collection, with the intervening values the results of successive applications of init.
returns
an iterator over all the inits of this traversable collection
Definition Classes
TraversableLike
Example:
1. List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)
def isEmpty: Boolean
Tests whether this traversable collection is empty.
Tests whether this traversable collection is empty.
returns
true if the traversable collection contain no elements, false otherwise.

Definition Classes
TraversableLike → TraversableOnce → GenTraversableOnce
final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object is T0.
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.
returns
true if the receiver object is an instance of erasure of type T0; false otherwise.

Definition Classes
Any
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
TraversableLike → GenTraversableLike → GenTraversableOnce
def last: A
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 traversable collection.

Definition Classes
TraversableLike → GenTraversableLike
Exceptions thrown
NoSuchElementException If the traversable collection is empty.
def lastOption: Option[A]
Optionally selects the last element.
Optionally selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
returns
the last element of this traversable collection$ if it is nonempty, None if it is empty.

Definition Classes
TraversableLike → GenTraversableLike
def map[B](f: (A) ⇒ B): Traversable[B]
[use case] Builds a new collection by applying a function to all elements of this collection.
[use case]
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.

Definition Classes
TraversableLike → GenTraversableLike → FilterMonadic
Full Signature
def map[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Traversable[A], B, That]): That
def max: A
[use case] Finds the largest element.
[use case]
Finds the largest element.
returns
the largest element of this collection.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def max[B >: A](implicit cmp: Ordering[B]): A
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 collection with the largest value measured by function f.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
def min: A
[use case] Finds the smallest element.
[use case]
Finds the smallest element.
returns
the smallest element of this collection

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def min[B >: A](implicit cmp: Ordering[B]): A
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 collection with the smallest value measured by function f.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
def mkString: String
Displays all elements of this traversable or iterator in a string.
Displays all elements of this traversable or iterator in a string.
returns
a string representation of this traversable or iterator. In the resulting string the string representations (w.r.t. the method toString) of all elements of this traversable or iterator follow each other without any separator string.

Definition Classes
TraversableOnce → GenTraversableOnce
def mkString(sep: String): String
Displays all elements of this traversable or iterator in a string using a separator string.
Displays all elements of this traversable or iterator in a string using a separator string.
sep
the separator string.
returns
a string representation of this traversable or iterator. In the resulting string the string representations (w.r.t. the method toString) of all elements of this traversable or iterator are separated by the string sep.
Definition Classes
TraversableOnce → GenTraversableOnce
Example:
1. List(1, 2, 3).mkString("|") = "1|2|3"
def mkString(start: String, sep: String, end: String): String
Displays all elements of this traversable or iterator in a string using start, end, and separator strings.
Displays all elements of this traversable or iterator in a string using start, end, and separator strings.
start
the starting string.
sep
the separator string.
end
the ending string.
returns
a string representation of this traversable or iterator. The resulting string begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this traversable or iterator are separated by the string sep.
Definition Classes
TraversableOnce → GenTraversableOnce
Example:
1. List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
final def ne(arg0: AnyRef): Boolean
Equivalent to !(this eq that).
Equivalent to !(this eq that).
returns
true if the argument is not a reference to the receiver object; false otherwise.

Definition Classes
AnyRef
def newBuilder: Builder[A, Traversable[A]]
The builder that builds instances of type Traversable[A]
The builder that builds instances of type Traversable[A]

Attributes
protected[this]
Definition Classes
GenericTraversableTemplate → HasNewBuilder
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
TraversableOnce → GenTraversableOnce
final def notify(): Unit
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.

Definition Classes
AnyRef
Annotations
@native()
Note
not specified by SLS as a member of AnyRef
final def notifyAll(): Unit
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.

Definition Classes
AnyRef
Annotations
@native()
Note
not specified by SLS as a member of AnyRef
def par: ParIterable[A]
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
def parCombiner: Combiner[A, ParIterable[A]]
The default par implementation uses the combiner provided by this method to create a new parallel collection.
The default par implementation uses the combiner provided by this method to create a new parallel collection.
returns
a combiner for the parallel collection of type ParRepr

Attributes
protected[this]
Definition Classes
TraversableLike → Parallelizable
def partition(p: (A) ⇒ Boolean): (Traversable[A], Traversable[A])
Partitions this traversable collection in two traversable collections according to a predicate.
Partitions this traversable collection in two traversable collections according to a predicate.
p
the predicate on which to partition.
returns
a pair of traversable collections: the first traversable collection consists of all elements that satisfy the predicate p and the second traversable collection consists of all elements that don't. The relative order of the elements in the resulting traversable collections is the same as in the original traversable collection.

Definition Classes
TraversableLike → GenTraversableLike
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 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 collection and as result type of product. Examples of such types are: Long, Float, Double, BigInt.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def product[B >: A](implicit num: Numeric[B]): B
def reduce[A1 >: A](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
TraversableOnce → GenTraversableOnce
Exceptions thrown
UnsupportedOperationException if this traversable or iterator is empty.
def reduceLeft[B >: A](op: (B, A) ⇒ 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, ..., x_n are the elements of this traversable or iterator.
Definition Classes
TraversableOnce
Exceptions thrown
UnsupportedOperationException if this traversable or iterator is empty.
def reduceLeftOption[B >: A](op: (B, A) ⇒ 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
TraversableOnce → GenTraversableOnce
def reduceOption[A1 >: A](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
TraversableOnce → GenTraversableOnce
def reduceRight[B >: A](op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this traversable or iterator, going right to left.
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
the result of inserting op between consecutive elements of this traversable or iterator, going right to left:
```
op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
```
where x₁, ..., x_n are the elements of this traversable or iterator.
Definition Classes
TraversableOnce → GenTraversableOnce
Exceptions thrown
UnsupportedOperationException if this traversable or iterator is empty.
def reduceRightOption[B >: A](op: (A, 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
TraversableOnce → GenTraversableOnce
def repr: Traversable[A]
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
TraversableLike → GenTraversableLike
def reversed: scala.List[A]

Attributes
protected[this]
Definition Classes
TraversableOnce
def scan[B >: A, That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Traversable[A], 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
TraversableLike → GenTraversableLike
def scanLeft[B, That](z: B)(op: (B, A) ⇒ B)(implicit bf: CanBuildFrom[Traversable[A], 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
TraversableLike → GenTraversableLike
def scanRight[B, That](z: B)(op: (A, B) ⇒ B)(implicit bf: CanBuildFrom[Traversable[A], 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
TraversableLike → GenTraversableLike
Annotations
@migration
Migration
(Changed in version 2.9.0) The behavior of scanRight has changed. The previous behavior can be reproduced with scanRight.reverse.
def seq: Traversable[A]
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
Traversable → Traversable → GenTraversable → Parallelizable → TraversableOnce → GenTraversableOnce
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
TraversableOnce → GenTraversableOnce
def sizeHintIfCheap: Int
The size of this collection or iterator, if it can be cheaply computed
The size of this collection or iterator, if it can be cheaply computed
returns
the number of elements in this collection or iterator, or -1 if the size cannot be determined cheaply

Attributes
protected[scala.collection]
Definition Classes
GenTraversableOnce
def slice(from: Int, until: Int): Traversable[A]
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 traversable collection containing the elements greater than or equal to index from extending up to (but not including) index until of this traversable collection.

Definition Classes
TraversableLike → GenTraversableLike
def span(p: (A) ⇒ Boolean): (Traversable[A], Traversable[A])
Splits this traversable collection into a prefix/suffix pair according to a predicate.
Splits this traversable 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 traversable collection whose elements all satisfy p, and the rest of this traversable collection.

Definition Classes
TraversableLike → GenTraversableLike
def splitAt(n: Int): (Traversable[A], Traversable[A])
Splits this traversable collection into two at a given position.
Splits this traversable 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 traversable collections consisting of the first n elements of this traversable collection, and the other elements.

Definition Classes
TraversableLike → GenTraversableLike
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 traversable collection. By default the string prefix is the simple name of the collection class traversable collection.

Definition Classes
TraversableLike → GenTraversableLike
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 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 collection and as result type of sum. Examples of such types are: Long, Float, Double, BigInt.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def sum[B >: A](implicit num: Numeric[B]): B
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
def tail: Traversable[A]
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 traversable collection consisting of all elements of this traversable collection except the first one.

Definition Classes
TraversableLike → GenTraversableLike
Exceptions thrown
`UnsupportedOperationException` if the traversable collection is empty.
def tails: Iterator[Traversable[A]]
Iterates over the tails of this traversable collection.
Iterates over the tails of this traversable collection. The first value will be this traversable collection and the final one will be an empty traversable collection, with the intervening values the results of successive applications of tail.
returns
an iterator over all the tails of this traversable collection
Definition Classes
TraversableLike
Example:
1. List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)
def take(n: Int): Traversable[A]
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 traversable collection.
returns
a traversable collection consisting only of the first n elements of this traversable collection, or else the whole traversable collection, if it has less than n elements.

Definition Classes
TraversableLike → GenTraversableLike
def takeWhile(p: (A) ⇒ Boolean): Traversable[A]
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 traversable collection whose elements all satisfy the predicate p.

Definition Classes
TraversableLike → GenTraversableLike
def thisCollection: collection.Traversable[A]
The underlying collection seen as an instance of Traversable.
The underlying collection seen as an instance of Traversable. By default this is implemented as the current collection object itself, but this can be overridden.

Attributes
protected[this]
Definition Classes
TraversableLike
def to[Col[_]]: Col[A]
[use case] Converts this collection into another by copying all elements.
[use case]
Converts this 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 collection.

Definition Classes
TraversableLike → TraversableOnce → GenTraversableOnce
Full Signature
def to[Col[_]](implicit cbf: CanBuildFrom[Nothing, A, Col[A]]): Col[A]
def toArray: Array[A]
[use case] Converts this collection to an array.
[use case]
Converts this collection to an array.
Note: will not terminate for infinite-sized collections.
returns
an array containing all elements of this collection. An ClassTag must be available for the element type of this collection.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]
def toBuffer[B >: A]: 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
TraversableOnce → GenTraversableOnce
def toCollection(repr: Traversable[A]): collection.Traversable[A]
A conversion from collections of type Repr to Traversable objects.
A conversion from collections of type Repr to Traversable objects. By default this is implemented as just a cast, but this can be overridden.

Attributes
protected[this]
Definition Classes
TraversableLike
def toIndexedSeq: IndexedSeq[A]
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
TraversableOnce → GenTraversableOnce
def toIterable: collection.Iterable[A]
Converts this traversable or iterator to an iterable collection.
Converts this traversable or iterator to an iterable collection. Note that the choice of target Iterable is lazy in this default implementation as this TraversableOnce may be lazy and unevaluated (i.e. it may be an iterator which is only traversable once).
Note: will not terminate for infinite-sized collections.
returns
an Iterable containing all elements of this traversable or iterator.

Definition Classes
TraversableOnce → GenTraversableOnce
def toIterator: Iterator[A]
Returns an Iterator over the elements in this traversable collection.
Returns an Iterator over the elements in this traversable collection. Will return the same Iterator if this instance is already an Iterator.
Note: will not terminate for infinite-sized collections.
returns
an Iterator containing all elements of this traversable collection.

Definition Classes
TraversableLike → GenTraversableOnce
def toList: scala.List[A]
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
TraversableOnce → GenTraversableOnce
def toMap[T, U]: collection.Map[T, U]
[use case] Converts this collection to a map.
[use case]
Converts this 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 collection.

Definition Classes
TraversableOnce → GenTraversableOnce
Full Signature
def toMap[T, U](implicit ev: <:<[A, (T, U)]): Map[T, U]
def toParArray: ParArray[T]

Implicit
This member is added by an implicit conversion from Traversable[A] to CollectionsHaveToParArray[Traversable[A], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (Traversable[A]) ⇒ GenTraversableOnce[T] is in scope.
Definition Classes
CollectionsHaveToParArray
def toSeq: collection.Seq[A]
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
TraversableOnce → GenTraversableOnce
def toSet[B >: A]: 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
TraversableOnce → GenTraversableOnce
def toStream: scala.Stream[A]
Converts this traversable collection to a stream.
Converts this traversable collection to a stream.
returns
a stream containing all elements of this traversable collection.

Definition Classes
TraversableLike → GenTraversableOnce
def toString(): String
Converts this traversable collection to a string.
Converts this traversable collection to a string.
returns
a string representation of this collection. By default this string consists of the stringPrefix of this traversable collection, followed by all elements separated by commas and enclosed in parentheses.

Definition Classes
TraversableLike → Any
def toTraversable: collection.Traversable[A]
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
TraversableLike → TraversableOnce → GenTraversableOnce
Annotations
@deprecatedOverriding( message = ... , since = "2.11.0" )
def toVector: scala.Vector[A]
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
TraversableOnce → GenTraversableOnce
def transpose[B](implicit asTraversable: (A) ⇒ GenTraversableOnce[B]): Traversable[Traversable[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.
def unzip[A1, A2](implicit asPair: (A) ⇒ (A1, A2)): (Traversable[A1], Traversable[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
GenericTraversableTemplate
def unzip3[A1, A2, A3](implicit asTriple: (A) ⇒ (A1, A2, A3)): (Traversable[A1], Traversable[A2], Traversable[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
GenericTraversableTemplate
def view(from: Int, until: Int): TraversableView[A, Traversable[A]]
Creates a non-strict view of a slice of this traversable collection.
Creates a non-strict view of a slice of this traversable collection.
Note: the difference between view and slice is that view produces a view of the current traversable collection, whereas slice produces a new traversable 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 traversable collection, starting at index from and extending up to (but not including) index until.

Definition Classes
TraversableLike
def view: TraversableView[A, Traversable[A]]
Creates a non-strict view of this traversable collection.
Creates a non-strict view of this traversable collection.
returns
a non-strict view of this traversable collection.

Definition Classes
TraversableLike
final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@native() @throws( ... )
def withFilter(p: (A) ⇒ Boolean): FilterMonadic[A, Traversable[A]]
Creates a non-strict filter of this traversable collection.
Creates a non-strict filter of this traversable 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 traversable collection which satisfy the predicate p.

Definition Classes
TraversableLike → FilterMonadic
def →[B](y: B): (Traversable[A], B)

Implicit
This member is added by an implicit conversion from Traversable[A] to ArrowAssoc[Traversable[A]] performed by method ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc

Shadowed Implicit Value Members

def filter(p: (A) ⇒ Boolean): TraversableOnce[A]
Implicit
This member is added by an implicit conversion from Traversable[A] to MonadOps[A] 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:
(traversable: MonadOps[A]).filter(p)
Definition Classes
MonadOps
def flatMap[B](f: (A) ⇒ GenTraversableOnce[B]): TraversableOnce[B]
Implicit
This member is added by an implicit conversion from Traversable[A] to MonadOps[A] 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:
(traversable: MonadOps[A]).flatMap(f)
Definition Classes
MonadOps
def map[B](f: (A) ⇒ B): TraversableOnce[B]
Implicit
This member is added by an implicit conversion from Traversable[A] to MonadOps[A] 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:
(traversable: MonadOps[A]).map(f)
Definition Classes
MonadOps
def withFilter(p: (A) ⇒ Boolean): Iterator[A]
Implicit
This member is added by an implicit conversion from Traversable[A] to MonadOps[A] 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:
(traversable: MonadOps[A]).withFilter(p)
Definition Classes
MonadOps

Packages

Package structure

Automatic imports

Guide

Using Collections

Creating Collections

Converting to and from Java Collections

Traversable 

Companion object Traversable

trait Traversable[+A] extends collection.Traversable[A] with GenericTraversableTemplate[A, Traversable] with TraversableLike[A, Traversable[A]] with Immutable

Type Members

Value Members

def ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Traversable[A], B, That]): That

def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Traversable[A], B, That]): That

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

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

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

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

def flatten[B](implicit asTraversable: (A) ⇒ GenTraversableOnce[B]): Traversable[B]

abstract def foreach[U](f: (A) ⇒ U): Unit

def map[B, That](f: (A) ⇒ B)(implicit bf: CanBuildFrom[Traversable[A], B, That]): That

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

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

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

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

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

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

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

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

def toMap[T, U](implicit ev: <:<[A, (T, U)]): Map[T, U]

Shadowed Implicit Value Members

Inherited from Immutable

Inherited from collection.Traversable[A]

Inherited from GenTraversable[A]

Inherited from GenericTraversableTemplate[A, Traversable]

Inherited from TraversableLike[A, Traversable[A]]

Inherited from GenTraversableLike[A, Traversable[A]]

Inherited from Parallelizable[A, ParIterable[A]]

Inherited from TraversableOnce[A]

Inherited from GenTraversableOnce[A]

Inherited from FilterMonadic[A, Traversable[A]]

Inherited from HasNewBuilder[A, scala.collection.immutable.Traversable[A] @scala.annotation.unchecked.uncheckedVariance]

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion CollectionsHaveToParArray from Traversable[A] to CollectionsHaveToParArray[Traversable[A], T]

Inherited by implicit conversion MonadOps from Traversable[A] to MonadOps[A]

Inherited by implicit conversion any2stringadd from Traversable[A] to any2stringadd[Traversable[A]]

Inherited by implicit conversion StringFormat from Traversable[A] to StringFormat[Traversable[A]]

Inherited by implicit conversion Ensuring from Traversable[A] to Ensuring[Traversable[A]]

Inherited by implicit conversion ArrowAssoc from Traversable[A] to ArrowAssoc[Traversable[A]]

Inherited by implicit conversion alternateImplicit from Traversable[A] to ForceImplicitAmbiguity

Ungrouped

Traversable