scala.collection.TraversableProxyLike

trait TraversableProxyLike[+A, +Repr <: TraversableLike[A, Repr] with Traversable[A]] extends TraversableLike[A, Repr] with Proxy

This trait implements a proxy for Traversable objects. It forwards all calls to a different Traversable object.

• Annotations
  • @ deprecated
• Deprecated
  • (Since version 2.11.0) Proxying is deprecated due to lack of use and compiler-level support.
• Source
  • TraversableProxyLike.scala - Blame
  • TraversableProxyLike.scala - History
• Version
  • 2.8
• Since
  • 2.8

Type Members

type Self = Repr

The type implementing this traversable

• Attributes
  • protected[this]
• Definition Classes
  • TraversableLike

class WithFilter extends FilterMonadic[A, Repr]

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

• Definition Classes
  • TraversableLike

Concrete Value Members From scala.Proxy

def equals(that: Any): Boolean

Compares the receiver object ( this ) with the argument object ( that ) for equivalence.

Any implementation of this method should be an equivalence relation :

• It is reflexive: for any instance x of type Any , x.equals(x) should return true .
• It is symmetric: for any instances x and y of type Any , x.equals(y) should return true if and only if y.equals(x) returns true .
• It is transitive: for any instances x , y , and z of type Any if x.equals(y) returns true and y.equals(z) returns true , then x.equals(z) should return true .

If you override this method, you should verify that your implementation remains an equivalence relation. Additionally, when overriding this method it is usually necessary to override hashCode to ensure that objects which are “equal” ( o1.equals(o2) returns true ) hash to the same scala.Int. ( o1.hashCode.equals(o2.hashCode) ).

• that
  • the object to compare against this object for equality.
• returns
  • true if the receiver object is equivalent to the argument; false otherwise.
• Definition Classes
  • Proxy → Any

(defined at scala.Proxy)

Abstract Value Members From scala.collection.Parallelizable

abstract def seq: TraversableOnce[A]

• Definition Classes
  • Parallelizable

(defined at scala.collection.Parallelizable)

Concrete Value Members From scala.collection.Parallelizable

def par: ParIterable[A]

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

(defined at scala.collection.Parallelizable)

Abstract Value Members From scala.collection.TraversableLike

abstract def newBuilder: Builder[A, Repr]

Creates a new builder for this collection type.

• Attributes
  • protected[this]
• Definition Classes
  • TraversableLike → HasNewBuilder

(defined at scala.collection.TraversableLike)

Concrete Value Members From scala.collection.TraversableLike

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

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 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

(defined at scala.collection.TraversableLike)

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

[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 traversable collection which contains all elements of this traversable collection followed by all elements of that .
• Definition Classes
  • TraversableLike

(defined at scala.collection.TraversableLike)

def parCombiner: Combiner[A, ParIterable[A]]

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

(defined at scala.collection.TraversableLike)

def scan[B >: A, That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Repr, B, That]): That

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

(defined at scala.collection.TraversableLike)

def toCollection(repr: Repr): Traversable[A]

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

(defined at scala.collection.TraversableLike)

def withFilter(p: (A) ⇒ Boolean): FilterMonadic[A, Repr]

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

(defined at scala.collection.TraversableLike)

Concrete Value Members From scala.collection.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.

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

(defined at scala.collection.TraversableOnce)

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.

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:

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

(defined at scala.collection.TraversableOnce)

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.

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

(defined at scala.collection.TraversableOnce)

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

[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 traversable collection with the largest value measured by function f.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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

[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 traversable collection with the smallest value measured by function f.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableOnce)

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.

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

(defined at scala.collection.TraversableOnce)

def reduce[A1 >: A](op: (A1, A1) ⇒ A1): A1

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.

(defined at scala.collection.TraversableOnce)

Concrete Value Members From scala.collection.TraversableProxyLike

abstract def self: Repr

• Definition Classes
  • TraversableProxyLike → Proxy

(defined at scala.collection.TraversableProxyLike)

def ++[B >: A, That](xs: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That

[use case]

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.

Example:

scala> val a = List(1)
a: List[Int] = List(1)

scala> val b = List(2)
b: List[Int] = List(2)

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

scala> val d = List('a')
d: List[Char] = List(a)

scala> val e = c ++ d
e: List[AnyVal] = List(1, 2, a)

• B
  • the element type of the returned collection.
• that
  • the traversable to append.
• returns
  • a new traversable collection which contains all elements of this traversable collection followed by all elements of that .
• Definition Classes
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def /:[B](z: B)(op: (B, A) ⇒ B): B

Applies a binary operator to a start value and all elements of this traversable collection, 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 collection, 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 collection.

• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def :\[B](z: B)(op: (A, B) ⇒ B): B

Applies a binary operator to all elements of this traversable collection 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 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 traversable collection.

• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def addString(b: mutable.StringBuilder): mutable.StringBuilder

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

Example:

scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)

scala> val b = new StringBuilder()
b: StringBuilder =

scala> val h = a.addString(b)
h: StringBuilder = 1234

• b
  • the string builder to which elements are appended.
• returns
  • the string builder b to which elements were appended.
• Definition Classes
  • TraversableProxyLike → TraversableOnce

(defined at scala.collection.TraversableProxyLike)

def addString(b: mutable.StringBuilder, sep: String): mutable.StringBuilder

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

Example:

scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)

scala> val b = new StringBuilder()
b: StringBuilder =

scala> a.addString(b, ", ")
res0: StringBuilder = 1, 2, 3, 4

• b
  • the string builder to which elements are appended.
• sep
  • the separator string.
• returns
  • the string builder b to which elements were appended.
• Definition Classes
  • TraversableProxyLike → TraversableOnce

(defined at scala.collection.TraversableProxyLike)

def addString(b: mutable.StringBuilder, start: String, sep: String, end: String): mutable.StringBuilder

Appends all elements of this traversable collection 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 collection 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
  • TraversableProxyLike → TraversableOnce

(defined at scala.collection.TraversableProxyLike)

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

[use case]

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

• B
  • the element type of the returned collection.
• pf
  • the partial function which filters and maps the traversable collection.
• returns
  • a new traversable 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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

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

[use case]

Copies the elements of this traversable collection to an array. Fills the given array xs with values of this traversable collection. Copying will stop once either the end of the current traversable 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
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

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

[use case]

Copies the elements of this traversable collection to an array. Fills the given array xs with values of this traversable collection, beginning at index start . Copying will stop once either the end of the current traversable 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
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

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

[use case]

Copies the elements of this traversable collection to an array. Fills the given array xs with at most len elements of this traversable collection, starting at position start . Copying will stop once either the end of the current traversable 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
  • TraversableProxyLike → TraversableLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

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

Copies all elements of this traversable collection to a buffer.

Note: will not terminate for infinite-sized collections.

• dest
  • The buffer to which elements are copied.
• Definition Classes
  • TraversableProxyLike → TraversableOnce

(defined at scala.collection.TraversableProxyLike)

def count(p: (A) ⇒ Boolean): Int

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

• p
  • the predicate used to test elements.
• returns
  • the number of elements satisfying the predicate p .
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def drop(n: Int): Repr

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def dropWhile(p: (A) ⇒ Boolean): Repr

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def exists(p: (A) ⇒ Boolean): Boolean

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
  • TraversableProxyLike → TraversableLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def filter(p: (A) ⇒ Boolean): Repr

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def filterNot(p: (A) ⇒ Boolean): Repr

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def find(p: (A) ⇒ Boolean): Option[A]

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
  • TraversableProxyLike → TraversableLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

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

[use case]

Builds a new collection by applying a function to all elements of this traversable 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 traversable 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 traversable collection resulting from applying the given collection-valued function f to each element of this traversable collection and concatenating the results.
• Definition Classes
  • TraversableProxyLike → TraversableLike → GenTraversableLike → FilterMonadic

(defined at scala.collection.TraversableProxyLike)

def foldLeft[B](z: B)(op: (B, A) ⇒ B): B

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this traversable collection, 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 collection. Returns
 `z` if this traversable collection is empty.

• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def foldRight[B](z: B)(op: (A, B) ⇒ B): B

Applies a binary operator to all elements of this traversable 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 traversable 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 traversable collection. Returns
 `z` if this traversable collection is empty.

• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def forall(p: (A) ⇒ Boolean): Boolean

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
  • TraversableProxyLike → TraversableLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def foreach[U](f: (A) ⇒ U): Unit

[use case]

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

Note: this method underlies the implementation of most other bulk operations. It’s important to implement this method in an efficient way.

• f
  • the function that is applied for its side-effect to every element. The result of function f is discarded.
• Definition Classes
  • TraversableProxyLike → TraversableLike → GenTraversableLike → TraversableOnce → GenTraversableOnce → FilterMonadic

(defined at scala.collection.TraversableProxyLike)

def groupBy[K](f: (A) ⇒ K): immutable.Map[K, Repr]

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

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

[use case]

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

• B
  • the element type of the returned collection.
• f
  • the function to apply to each element.
• returns
  • a new traversable collection resulting from applying the given function f to each element of this traversable collection and collecting the results.
• Definition Classes
  • TraversableProxyLike → TraversableLike → GenTraversableLike → FilterMonadic

(defined at scala.collection.TraversableProxyLike)

def mkString(sep: String): String

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

• sep
  • the separator string.
• returns
  • a string representation of this traversable collection. In the resulting string the string representations (w.r.t. the method toString ) of all elements of this traversable collection are separated by the string sep .
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

Example:

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

(defined at scala.collection.TraversableProxyLike)

def mkString(start: String, sep: String, end: String): String

Displays all elements of this traversable collection 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 collection. The resulting string begins with the string start and ends with the string end . Inside, the string representations (w.r.t. the method toString ) of all elements of this traversable collection are separated by the string sep .
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

Example:

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

(defined at scala.collection.TraversableProxyLike)

def partition(p: (A) ⇒ Boolean): (Repr, Repr)

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

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

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • an option value containing the result of reduceLeft(op) if this traversable collection is nonempty, None otherwise.
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

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

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this traversable collection, 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 collection.

• Definition Classes
  • TraversableProxyLike → TraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this traversable collection is empty.

(defined at scala.collection.TraversableProxyLike)

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

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • an option value containing the result of reduceRight(op) if this traversable collection is nonempty, None otherwise.
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def reduceRight[B >: A](op: (A, B) ⇒ B): B

Applies a binary operator to all elements of this traversable 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 traversable 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 traversable collection.

• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this traversable collection is empty.

(defined at scala.collection.TraversableProxyLike)

def scanLeft[B, That](z: B)(op: (B, A) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That

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 and the new element type B .
• returns
  • collection with intermediate results
• Definition Classes
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def scanRight[B, That](z: B)(op: (A, B) ⇒ B)(implicit bf: CanBuildFrom[Repr, B, That]): That

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 and the new element type B .
• returns
  • collection with intermediate results
• Definition Classes
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def slice(from: Int, until: Int): Repr

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def span(p: (A) ⇒ Boolean): (Repr, Repr)

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def splitAt(n: Int): (Repr, Repr)

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def take(n: Int): Repr

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def takeWhile(p: (A) ⇒ Boolean): Repr

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def toBuffer[B >: A]: Buffer[B]

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

Note: will not terminate for infinite-sized collections.

• returns
  • a buffer containing all elements of this traversable collection.
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def toIndexedSeq: immutable.IndexedSeq[A]

Converts this traversable collection to an indexed sequence.

Note: will not terminate for infinite-sized collections.

• returns
  • an indexed sequence containing all elements of this traversable collection.
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

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

[use case]

Converts this traversable 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 traversable collection.
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def toSet[B >: A]: immutable.Set[B]

Converts this traversable collection to a set.

Note: will not terminate for infinite-sized collections.

• returns
  • a set containing all elements of this traversable collection.
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def view(from: Int, until: Int): TraversableView[A, Repr]

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
  • TraversableProxyLike → TraversableLike

(defined at scala.collection.TraversableProxyLike)

def view: TraversableView[A, Repr]

Creates a non-strict view of this traversable collection.

• returns
  • a non-strict view of this traversable collection.
• Definition Classes
  • TraversableProxyLike → TraversableLike

(defined at scala.collection.TraversableProxyLike)

Concrete Value Members From Implicit scala.collection.parallel.CollectionsHaveToParArray ——————————————————————————–

def toParArray: ParArray[T]

• Implicit information
  • This member is added by an implicit conversion from TraversableProxyLike [A, Repr] to CollectionsHaveToParArray [TraversableProxyLike [A, Repr], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type ( TraversableProxyLike [A, Repr]) ⇒ GenTraversableOnce [T] is in scope.
• Definition Classes
  • CollectionsHaveToParArray (added by implicit convertion: scala.collection.parallel.CollectionsHaveToParArray)

Full Source:

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala
package collection

import generic._
import mutable.{Buffer, StringBuilder}
import scala.reflect.ClassTag

// Methods could be printed by  cat TraversableLike.scala | egrep '^  (override )?def'

/** This trait implements a proxy for Traversable objects. It forwards
 *  all calls to a different Traversable object.
 *
 *  @author  Martin Odersky
 *  @version 2.8
 *  @since   2.8
 */
@deprecated("Proxying is deprecated due to lack of use and compiler-level support.", "2.11.0")
trait TraversableProxyLike[+A, +Repr <: TraversableLike[A, Repr] with Traversable[A]] extends TraversableLike[A, Repr] with Proxy {
  def self: Repr

  override def foreach[U](f: A => U): Unit = self.foreach(f)
  override def isEmpty: Boolean = self.isEmpty
  override def nonEmpty: Boolean = self.nonEmpty
  override def size: Int = self.size
  override def hasDefiniteSize = self.hasDefiniteSize
  override def ++[B >: A, That](xs: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = self.++(xs)(bf)
  override def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = self.map(f)(bf)
  override def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = self.flatMap(f)(bf)
  override def filter(p: A => Boolean): Repr = self.filter(p)
  override def filterNot(p: A => Boolean): Repr = self.filterNot(p)
  override def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That = self.collect(pf)(bf)
  override def partition(p: A => Boolean): (Repr, Repr) = self.partition(p)
  override def groupBy[K](f: A => K): immutable.Map[K, Repr] = self.groupBy(f)
  override def forall(p: A => Boolean): Boolean = self.forall(p)
  override def exists(p: A => Boolean): Boolean = self.exists(p)
  override def count(p: A => Boolean): Int = self.count(p)
  override def find(p: A => Boolean): Option[A] = self.find(p)
  override def foldLeft[B](z: B)(op: (B, A) => B): B = self.foldLeft(z)(op)
  override def /: [B](z: B)(op: (B, A) => B): B = self./:(z)(op)
  override def foldRight[B](z: B)(op: (A, B) => B): B = self.foldRight(z)(op)
  override def :\ [B](z: B)(op: (A, B) => B): B = self.:\(z)(op)
  override def reduceLeft[B >: A](op: (B, A) => B): B = self.reduceLeft(op)
  override def reduceLeftOption[B >: A](op: (B, A) => B): Option[B] = self.reduceLeftOption(op)
  override def reduceRight[B >: A](op: (A, B) => B): B = self.reduceRight(op)
  override def reduceRightOption[B >: A](op: (A, B) => B): Option[B] = self.reduceRightOption(op)
  override def scanLeft[B, That](z: B)(op: (B, A) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = self.scanLeft(z)(op)(bf)
  override def scanRight[B, That](z: B)(op: (A, B) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = self.scanRight(z)(op)(bf)
  override def sum[B >: A](implicit num: Numeric[B]): B = self.sum(num)
  override def product[B >: A](implicit num: Numeric[B]): B = self.product(num)
  override def min[B >: A](implicit cmp: Ordering[B]): A = self.min(cmp)
  override def max[B >: A](implicit cmp: Ordering[B]): A = self.max(cmp)
  override def head: A = self.head
  override def headOption: Option[A] = self.headOption
  override def tail: Repr = self.tail
  override def last: A = self.last
  override def lastOption: Option[A] = self.lastOption
  override def init: Repr = self.init
  override def take(n: Int): Repr = self.take(n)
  override def drop(n: Int): Repr = self.drop(n)
  override def slice(from: Int, until: Int): Repr = self.slice(from, until)
  override def takeWhile(p: A => Boolean): Repr = self.takeWhile(p)
  override def dropWhile(p: A => Boolean): Repr = self.dropWhile(p)
  override def span(p: A => Boolean): (Repr, Repr) = self.span(p)
  override def splitAt(n: Int): (Repr, Repr) = self.splitAt(n)
  override def copyToBuffer[B >: A](dest: Buffer[B]) = self.copyToBuffer(dest)
  override def copyToArray[B >: A](xs: Array[B], start: Int, len: Int) = self.copyToArray(xs, start, len)
  override def copyToArray[B >: A](xs: Array[B], start: Int) = self.copyToArray(xs, start)
  override def copyToArray[B >: A](xs: Array[B]) = self.copyToArray(xs)
  override def toArray[B >: A: ClassTag]: Array[B] = self.toArray
  override def toList: List[A] = self.toList
  override def toIterable: Iterable[A] = self.toIterable
  override def toSeq: Seq[A] = self.toSeq
  override def toIndexedSeq: immutable.IndexedSeq[A] = self.toIndexedSeq
  override def toBuffer[B >: A] = self.toBuffer
  override def toStream: Stream[A] = self.toStream
  override def toSet[B >: A]: immutable.Set[B] = self.toSet
  override def toMap[T, U](implicit ev: A <:< (T, U)): immutable.Map[T, U] = self.toMap(ev)
  override def toTraversable: Traversable[A] = self.toTraversable
  override def toIterator: Iterator[A] = self.toIterator
  override def mkString(start: String, sep: String, end: String): String = self.mkString(start, sep, end)
  override def mkString(sep: String): String = self.mkString(sep)
  override def mkString: String = self.mkString
  override def addString(b: StringBuilder, start: String, sep: String, end: String): StringBuilder = self.addString(b, start, sep, end)
  override def addString(b: StringBuilder, sep: String): StringBuilder = self.addString(b, sep)
  override def addString(b: StringBuilder): StringBuilder = self.addString(b)
  override def stringPrefix : String = self.stringPrefix
  override def view = self.view
  override def view(from: Int, until: Int): TraversableView[A, Repr] = self.view(from, until)
  // This appears difficult to override due to the type of WithFilter.
  // override def withFilter(p: A => Boolean): WithFilter = self.withFilter(p)
}