scala.collection.MapProxyLike

trait MapProxyLike[A, +B, +This <: MapLike[A, B, This] with Map[A, B]] extends MapLike[A, B, This] with IterableProxyLike[(A, B), This]

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

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

Type Members

class DefaultKeySet extends AbstractSet[A] with Set[A] with Serializable

The implementation class of the set returned by keySet .

• Attributes
  • protected
• Definition Classes
  • MapLike

class DefaultValuesIterable extends AbstractIterable[B] with Iterable[B] with Serializable

The implementation class of the iterable returned by values .

• Attributes
  • protected
• Definition Classes
  • MapLike

class FilteredKeys extends AbstractMap[A, B] with DefaultMap[A, B]

• Attributes
  • protected
• Definition Classes
  • MapLike

class MappedValues[C] extends AbstractMap[A, C] with DefaultMap[A, C]

• Attributes
  • protected
• Definition Classes
  • MapLike

type Self = This

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.Function1

def compose[A](g: (A) ⇒ A): (A) ⇒ B

Composes two instances of Function1 in a new Function1, with this function applied last.

• A
  • the type to which function g can be applied
• g
  • a function A => T1
• returns
  • a new function f such that f(x) == apply(g(x))
• Definition Classes
  • Function1
• Annotations
  • @ unspecialized ()

(defined at scala.Function1)

Concrete Value Members From scala.PartialFunction

def andThen[C](k: (B) ⇒ C): PartialFunction[A, C]

Composes this partial function with a transformation function that gets applied to results of this partial function.

• C
  • the result type of the transformation function.
• k
  • the transformation function
• returns
  • a partial function with the same domain as this partial function, which maps arguments x to k(this(x)) .
• Definition Classes
  • PartialFunction → Function1

(defined at scala.PartialFunction)

def applyOrElse[A1 <: A, B1 >: B](x: A1, default: (A1) ⇒ B1): B1

Applies this partial function to the given argument when it is contained in the function domain. Applies fallback function where this partial function is not defined.

Note that expression pf.applyOrElse(x, default) is equivalent to

if(pf isDefinedAt x) pf(x) else default(x)

except that applyOrElse method can be implemented more efficiently. For all partial function literals the compiler generates an applyOrElse implementation which avoids double evaluation of pattern matchers and guards. This makes applyOrElse the basis for the efficient implementation for many operations and scenarios, such as:

• combining partial functions into orElse / andThen chains does not lead to excessive apply / isDefinedAt evaluation
• lift and unlift do not evaluate source functions twice on each invocation
• runWith allows efficient imperative-style combining of partial functions with conditionally applied actions

For non-literal partial function classes with nontrivial isDefinedAt method it is recommended to override applyOrElse with custom implementation that avoids double isDefinedAt evaluation. This may result in better performance and more predictable behavior w.r.t. side effects.

• x
  • the function argument
• default
  • the fallback function
• returns
  • the result of this function or fallback function application.
• Definition Classes
  • PartialFunction
• Since
  • 2.10

(defined at scala.PartialFunction)

def lift: (A) ⇒ Option[B]

Turns this partial function into a plain function returning an Option result.

• returns
  • a function that takes an argument x to Some(this(x)) if this is defined for x , and to None otherwise.
• Definition Classes
  • PartialFunction
• See also
  • Function.unlift

(defined at scala.PartialFunction)

def orElse[A1 <: A, B1 >: B](that: PartialFunction[A1, B1]): PartialFunction[A1, B1]

Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.

• A1
  • the argument type of the fallback function
• B1
  • the result type of the fallback function
• that
  • the fallback function
• returns
  • a partial function which has as domain the union of the domains of this partial function and that . The resulting partial function takes x to this(x) where this is defined, and to that(x) where it is not.
• Definition Classes
  • PartialFunction

(defined at scala.PartialFunction)

def runWith[U](action: (B) ⇒ U): (A) ⇒ Boolean

Composes this partial function with an action function which gets applied to results of this partial function. The action function is invoked only for its side effects; its result is ignored.

Note that expression pf.runWith(action)(x) is equivalent to

if(pf isDefinedAt x) { action(pf(x)); true } else false

except that runWith is implemented via applyOrElse and thus potentially more efficient. Using runWith avoids double evaluation of pattern matchers and guards for partial function literals.

• action
  • the action function
• returns
  • a function which maps arguments x to isDefinedAt(x) . The resulting function runs action(this(x)) where this is defined.
• Definition Classes
  • PartialFunction
• Since
  • 2.10
• See also
  • applyOrElse .

(defined at scala.PartialFunction)

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.GenMapLike

abstract def seq: Map[A, B]

• Definition Classes
  • GenMapLike → Parallelizable → GenTraversableOnce

(defined at scala.collection.GenMapLike)

Concrete Value Members From scala.collection.IterableLike

def canEqual(that: Any): Boolean

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

• that
  • The object with which this iterable collection should be compared
• returns
  • true , if this iterable collection can possibly equal that , false otherwise. The test takes into consideration only the run-time types of objects but ignores their elements.
• Definition Classes
  • IterableLike → Equals

(defined at scala.collection.IterableLike)

def thisCollection: Iterable[(A, B)]

The underlying collection seen as an instance of Iterable . By default this is implemented as the current collection object itself, but this can be overridden.

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

(defined at scala.collection.IterableLike)

def toCollection(repr: This): Iterable[(A, B)]

A conversion from collections of type Repr to Iterable objects. By default this is implemented as just a cast, but this can be overridden.

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

(defined at scala.collection.IterableLike)

Concrete Value Members From scala.collection.IterableProxyLike

def dropRight(n: Int): This

Selects all elements except last n ones.

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

• n
  • The number of elements to take
• returns
  • a iterable collection consisting of all elements of this iterable collection except the last n ones, or else the empty iterable collection, if this iterable collection has less than n elements.
• Definition Classes
  • IterableProxyLike → IterableLike

(defined at scala.collection.IterableProxyLike)

def grouped(size: Int): Iterator[This]

Partitions elements in fixed size iterable collections.

• size
  • the number of elements per group
• returns
  • An iterator producing iterable collections of size size , except the last will be less than size size if the elements don’t divide evenly.
• Definition Classes
  • IterableProxyLike → IterableLike
• See also
  • scala.collection.Iterator, method grouped

(defined at scala.collection.IterableProxyLike)

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

[use case]

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

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

• that
  • the collection to compare with.
• returns
  • true , if both collections contain the same elements in the same order, false otherwise.
• Definition Classes
  • IterableProxyLike → IterableLike → GenIterableLike

(defined at scala.collection.IterableProxyLike)

def sliding(size: Int): Iterator[This]

Groups elements in fixed size blocks by passing a “sliding window” over them (as opposed to partitioning them, as is done in grouped.) “Sliding window” step is 1 by default.

• size
  • the number of elements per group
• returns
  • An iterator producing iterable collections of size size , except the last and the only element will be truncated if there are fewer elements than size.
• Definition Classes
  • IterableProxyLike → IterableLike
• See also
  • scala.collection.Iterator, method sliding

(defined at scala.collection.IterableProxyLike)

def sliding(size: Int, step: Int): Iterator[This]

Groups elements in fixed size blocks by passing a “sliding window” over them (as opposed to partitioning them, as is done in grouped.)

• size
  • the number of elements per group
• step
  • the distance between the first elements of successive groups
• returns
  • An iterator producing iterable collections of size size , except the last and the only element will be truncated if there are fewer elements than size.
• Definition Classes
  • IterableProxyLike → IterableLike
• See also
  • scala.collection.Iterator, method sliding

(defined at scala.collection.IterableProxyLike)

def takeRight(n: Int): This

Selects last n elements.

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

• n
  • the number of elements to take
• returns
  • a iterable collection consisting only of the last n elements of this iterable collection, or else the whole iterable collection, if it has less than n elements.
• Definition Classes
  • IterableProxyLike → IterableLike

(defined at scala.collection.IterableProxyLike)

def view(from: Int, until: Int): IterableView[(A, B), This]

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

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

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

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

• from
  • the index of the first element of the view
• until
  • the index of the element following the view
• returns
  • a non-strict view of a slice of this iterable collection, starting at index from and extending up to (but not including) index until .
• Definition Classes
  • IterableProxyLike → TraversableProxyLike → IterableLike → TraversableLike

(defined at scala.collection.IterableProxyLike)

def view: IterableView[(A, B), This]

Creates a non-strict view of this iterable collection.

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

(defined at scala.collection.IterableProxyLike)

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

[use case]

Returns a map formed from this map and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.

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

• B
  • the type of the second half of the returned pairs
• that
  • The iterable providing the second half of each result pair
• thisElem
  • the element to be used to fill up the result if this map is shorter than that .
• thatElem
  • the element to be used to fill up the result if that is shorter than this map.
• returns
  • a new map containing pairs consisting of corresponding elements of this map and that . The length of the returned collection is the maximum of the lengths of this map and that . If this map is shorter than that , thisElem values are used to pad the result. If that is shorter than this map, thatElem values are used to pad the result.
• Definition Classes
  • IterableProxyLike → IterableLike → GenIterableLike

(defined at scala.collection.IterableProxyLike)

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

[use case]

Zips this map with its indices.

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

• returns
  • A new map containing pairs consisting of all elements of this map paired with their index. Indices start at 0 .
• Definition Classes
  • IterableProxyLike → IterableLike → GenIterableLike

Example:

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

(defined at scala.collection.IterableProxyLike)

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

[use case]

Returns a map formed from this map and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.

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

• B
  • the type of the second half of the returned pairs
• that
  • The iterable providing the second half of each result pair
• returns
  • a new map containing pairs consisting of corresponding elements of this map and that . The length of the returned collection is the minimum of the lengths of this map and that .
• Definition Classes
  • IterableProxyLike → IterableLike → GenIterableLike

(defined at scala.collection.IterableProxyLike)

Concrete Value Members From scala.collection.MapLike

abstract def empty: This

The empty map of the same type as this map

• returns
  • an empty map of type This .
• Definition Classes
  • MapLike

(defined at scala.collection.MapLike)

def newBuilder: Builder[(A, B), This]

A common implementation of newBuilder for all maps in terms of empty . Overridden for mutable maps in mutable.MapLike .

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

(defined at scala.collection.MapLike)

def parCombiner: Combiner[(A, B), ParMap[A, B]]

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
  • MapLike → TraversableLike → Parallelizable

(defined at scala.collection.MapLike)

Concrete Value Members From scala.collection.MapProxyLike

def +[B1 >: B](kv: (A, B1)): Map[A, B1]

[use case]

Adds a key/value pair to this map, returning a new map.

• kv
  • the key/value pair
• returns
  • a new map with the new binding added to this map
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike

(defined at scala.collection.MapProxyLike)

def +[B1 >: B](kv1: (A, B1), kv2: (A, B1), kvs: (A, B1)*): Map[A, B1]

[use case]

Adds key/value pairs to this map, returning a new map.

This method takes two or more key/value pairs. Another overloaded variant of this method handles the case where a single key/value pair is added.

• kvs
  • the key/value pairs
• returns
  • a new map with the given bindings added to this map
• Definition Classes
  • MapProxyLike → MapLike

(defined at scala.collection.MapProxyLike)

def ++[B1 >: B](xs: GenTraversableOnce[(A, B1)]): Map[A, B1]

[use case]

Adds all key/value pairs in a traversable collection to this map, returning a new map.

• xs
  • the collection containing the added key/value pairs
• returns
  • a new map with the given bindings added to this map
• Definition Classes
  • MapProxyLike → MapLike

(defined at scala.collection.MapProxyLike)

def -(key: A): This

[use case]

Removes a key from this map, returning a new map.

• key
  • the key to be removed
• returns
  • a new map without a binding for key
• Definition Classes
  • MapProxyLike → MapLike → Subtractable → GenMapLike

(defined at scala.collection.MapProxyLike)

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

Appends all elements of this map 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 map 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
  • MapProxyLike → TraversableProxyLike → MapLike → TraversableOnce

(defined at scala.collection.MapProxyLike)

def apply(key: A): B

Retrieves the value which is associated with the given key. This method invokes the default method of the map if there is no mapping from the given key to a value. Unless overridden, the default method throws a NoSuchElementException .

• key
  • the key
• returns
  • the value associated with the given key, or the result of the map’s default method, if none exists.
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike → Function1

(defined at scala.collection.MapProxyLike)

def contains(key: A): Boolean

Tests whether this map contains a binding for a key.

• key
  • the key
• returns
  • true if there is a binding for key in this map, false otherwise.
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike

(defined at scala.collection.MapProxyLike)

def default(key: A): B

Defines the default value computation for the map, returned when a key is not found The method implemented here throws an exception, but it might be overridden in subclasses.

• key
  • the given key value for which a binding is missing.
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike
• Exceptions thrown *

(defined at scala.collection.MapProxyLike)

def filterKeys(p: (A) ⇒ Boolean): Map[A, B]

Filters this map by retaining only keys satisfying a predicate.

Note : the predicate must accept any key of type A , not just those already present in the map, as the predicate is tested before the underlying map is queried.

• p
  • the predicate used to test keys
• returns
  • an immutable map consisting only of those key value pairs of this map where the key satisfies the predicate p . The resulting map wraps the original map without copying any elements.
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike

(defined at scala.collection.MapProxyLike)

def filterNot(p: ((A, B)) ⇒ Boolean): This

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

• p
  • the predicate used to test elements.
• returns
  • a new map consisting of all elements of this map that do not satisfy the given predicate p . The order of the elements is preserved.
• Definition Classes
  • MapProxyLike → TraversableProxyLike → MapLike → TraversableLike → GenTraversableLike

(defined at scala.collection.MapProxyLike)

def get(key: A): Option[B]

Optionally returns the value associated with a key.

• key
  • the key value
• returns
  • an option value containing the value associated with key in this map, or None if none exists.
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike

(defined at scala.collection.MapProxyLike)

def getOrElse[B1 >: B](key: A, default: ⇒ B1): B1

[use case]

Returns the value associated with a key, or a default value if the key is not contained in the map.

• key
  • the key.
• default
  • a computation that yields a default value in case no binding for key is found in the map.
• returns
  • the value associated with key if it exists, otherwise the result of the default computation.
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike

(defined at scala.collection.MapProxyLike)

def isDefinedAt(key: A): Boolean

Tests whether this map contains a binding for a key. This method, which implements an abstract method of trait PartialFunction , is equivalent to contains .

• key
  • the key
• returns
  • true if there is a binding for key in this map, false otherwise.
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike → PartialFunction

(defined at scala.collection.MapProxyLike)

def keySet: Set[A]

Collects all keys of this map in a set.

• returns
  • a set containing all keys of this map.
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike

(defined at scala.collection.MapProxyLike)

def mapValues[C](f: (B) ⇒ C): Map[A, C]

Transforms this map by applying a function to every retrieved value.

• f
  • the function used to transform values of this map.
• returns
  • a map view which maps every key of this map to f(this(key)) . The resulting map wraps the original map without copying any elements.
• Definition Classes
  • MapProxyLike → MapLike → GenMapLike

(defined at scala.collection.MapProxyLike)

def updated[B1 >: B](key: A, value: B1): Map[A, B1]

[use case]

Creates a new map obtained by updating this map with a given key/value pair.

• key
  • the key
• value
  • the value
• returns
  • A new map with the new key/value mapping added to this map.
• Definition Classes
  • MapProxyLike → MapLike

(defined at scala.collection.MapProxyLike)

Concrete Value Members From scala.collection.Parallelizable

def par: ParMap[A, B]

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)

Concrete Value Members From scala.collection.TraversableLike

def ++:[B >: (A, B), That](that: Traversable[B])(implicit bf: CanBuildFrom[This, 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, B), That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[This, 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 map which contains all elements of this map followed by all elements of that .
• Definition Classes
  • TraversableLike

(defined at scala.collection.TraversableLike)

def inits: Iterator[This]

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:

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

(defined at scala.collection.TraversableLike)

def repr: This

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

(defined at scala.collection.TraversableLike)

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

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:

List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)

(defined at scala.collection.TraversableLike)

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

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)) ⇒ 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), 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, B)](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)) ⇒ B)(implicit cmp: Ordering[B]): (A, B)

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

(defined at scala.collection.TraversableOnce)

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

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

(defined at scala.collection.TraversableOnce)

def reduceOption[A1 >: (A, B)](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, B)](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)

def reversed: List[(A, B)]

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

(defined at scala.collection.TraversableOnce)

def toVector: Vector[(A, B)]

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

(defined at scala.collection.TraversableOnce)

Abstract Value Members From scala.collection.TraversableProxyLike

abstract def self: This

• Definition Classes
  • TraversableProxyLike → Proxy

(defined at scala.collection.TraversableProxyLike)

Concrete Value Members From scala.collection.TraversableProxyLike

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

[use case]

Returns a new map containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the map 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 map which contains all elements of this map 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): 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): 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 collect[B, That](pf: PartialFunction[(A, B), B])(implicit bf: CanBuildFrom[This, B, That]): That

[use case]

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

• B
  • the element type of the returned collection.
• pf
  • the partial function which filters and maps the map.
• returns
  • a new map 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, B)](xs: Array[B]): Unit

[use case]

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

• xs
  • the array to fill.
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

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

[use case]

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

• xs
  • the array to fill.
• start
  • the starting index.
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

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

[use case]

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

• 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, B)](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, B)) ⇒ 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): This

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, B)) ⇒ Boolean): This

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, B)) ⇒ 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, B)) ⇒ Boolean): This

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 find(p: ((A, B)) ⇒ Boolean): Option[(A, B)]

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, B)) ⇒ GenTraversableOnce[B])(implicit bf: CanBuildFrom[This, B, That]): That

[use case]

Builds a new collection by applying a function to all elements of this map 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 map. 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 map resulting from applying the given collection-valued function f to each element of this map 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): 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): 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, B)) ⇒ 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, B)) ⇒ U): Unit

[use case]

Applies a function f to all elements of this map.

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, B)) ⇒ K): immutable.Map[K, This]

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 head: (A, B)

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike
• Exceptions thrown
  • NoSuchElementException if the traversable collection is empty.

(defined at scala.collection.TraversableProxyLike)

def headOption: Option[(A, B)]

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

def init: This

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike
• Exceptions thrown
  • UnsupportedOperationException if the traversable collection is empty.

(defined at scala.collection.TraversableProxyLike)

def last: (A, B)

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike
• Exceptions thrown
  • NoSuchElementException If the traversable collection is empty.

(defined at scala.collection.TraversableProxyLike)

def lastOption: Option[(A, B)]

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike

(defined at scala.collection.TraversableProxyLike)

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

[use case]

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

• B
  • the element type of the returned collection.
• f
  • the function to apply to each element.
• returns
  • a new map resulting from applying the given function f to each element of this map 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, B)) ⇒ Boolean): (This, This)

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, B)](op: (B, (A, B)) ⇒ 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, B)](op: (B, (A, B)) ⇒ 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, B)](op: ((A, B), 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, B)](op: ((A, B), 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)) ⇒ B)(implicit bf: CanBuildFrom[This, 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) ⇒ B)(implicit bf: CanBuildFrom[This, 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): This

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, B)) ⇒ Boolean): (This, This)

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): (This, This)

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 tail: This

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
  • TraversableProxyLike → TraversableLike → GenTraversableLike
• Exceptions thrown
  • UnsupportedOperationException if the traversable collection is empty.

(defined at scala.collection.TraversableProxyLike)

def take(n: Int): This

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, B)) ⇒ Boolean): This

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, B)]: 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, B)]

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 toIterable: Iterable[(A, B)]

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

(defined at scala.collection.TraversableProxyLike)

def toIterator: Iterator[(A, B)]

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
  • TraversableProxyLike → TraversableLike → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def toList: List[(A, B)]

Converts this traversable collection to a list.

Note: will not terminate for infinite-sized collections.

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

(defined at scala.collection.TraversableProxyLike)

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

[use case]

Converts this map 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.

• returns
  • a map of type immutable.Map[T, U] containing all key/value pairs of type (T, U) of this map.
• Definition Classes
  • TraversableProxyLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

def toSeq: Seq[(A, B)]

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

(defined at scala.collection.TraversableProxyLike)

def toSet[B >: (A, B)]: 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 toStream: Stream[(A, B)]

Converts this traversable collection to a stream.

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

(defined at scala.collection.TraversableProxyLike)

def toTraversable: Traversable[(A, B)]

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
  • TraversableProxyLike → TraversableLike → TraversableOnce → GenTraversableOnce

(defined at scala.collection.TraversableProxyLike)

Concrete Value Members From scala.collection.generic.Subtractable

def -(elem1: A, elem2: A, elems: A*): This

Creates a new collection from this collection with some elements removed.

This method takes two or more elements to be removed. Another overloaded variant of this method handles the case where a single element is removed.

• elem1
  • the first element to remove.
• elem2
  • the second element to remove.
• elems
  • the remaining elements to remove.
• returns
  • a new collection that contains all elements of the current collection except one less occurrence of each of the given elements.
• Definition Classes
  • Subtractable

(defined at scala.collection.generic.Subtractable)

def --(xs: GenTraversableOnce[A]): This

Creates a new collection from this collection by removing all elements of another collection.

• xs
  • the collection containing the removed elements.
• returns
  • a new collection that contains all elements of the current collection except one less occurrence of each of the elements of elems .
• Definition Classes
  • Subtractable

(defined at scala.collection.generic.Subtractable)

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

def toParArray: ParArray[T]

• Implicit information
  • This member is added by an implicit conversion from MapProxyLike [A, B, This] to CollectionsHaveToParArray [MapProxyLike [A, B, This], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (MapProxyLike [ A, B, This]) ⇒ 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

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

/** This trait implements a proxy for Map objects. It forwards
 *  all calls to a different Map 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 MapProxyLike[A, +B, +This <: MapLike[A, B, This] with Map[A, B]]
      extends MapLike[A, B, This]
      with IterableProxyLike[(A, B), This]
{
  override def get(key: A): Option[B] = self.get(key)
  override def iterator: Iterator[(A, B)] = self.iterator
  override def + [B1 >: B] (kv: (A, B1)): Map[A, B1] = self.+(kv)
  override def - (key: A): This = self.-(key)
  override def isEmpty: Boolean = self.isEmpty
  override def getOrElse[B1 >: B](key: A, default: => B1): B1 = self.getOrElse(key, default)
  override def apply(key: A): B = self.apply(key)
  override def contains(key: A): Boolean = self.contains(key)
  override def isDefinedAt(key: A) = self.isDefinedAt(key)
  override def keySet: Set[A] = self.keySet
  override def keysIterator: Iterator[A] = self.keysIterator
  override def keys: Iterable[A] = self.keys
  override def values: Iterable[B] = self.values
  override def valuesIterator: Iterator[B] = self.valuesIterator
  override def default(key: A): B = self.default(key)
  override def filterKeys(p: A => Boolean) = self.filterKeys(p)
  override def mapValues[C](f: B => C) = self.mapValues(f)
  override def updated [B1 >: B](key: A, value: B1): Map[A, B1] = self.updated(key, value)
  override def + [B1 >: B] (kv1: (A, B1), kv2: (A, B1), kvs: (A, B1) *): Map[A, B1] = self.+(kv1, kv2, kvs: _*)
  override def ++[B1 >: B](xs: GenTraversableOnce[(A, B1)]): Map[A, B1] =  self.++(xs)
  override def filterNot(p: ((A, B)) => Boolean) = self filterNot p

  override def addString(b: StringBuilder, start: String, sep: String, end: String): StringBuilder =
    self.addString(b, start, sep, end)
}