Map

scala.collection.concurrent.Map
trait Map[K, V] extends Map[K, V]

A template trait for mutable maps that allow concurrent access.

$concurrentmapinfo

Type parameters

K

the key type of the map

V

the value type of the map

Attributes

See also

"Scala's Collection Library overview" section on Concurrent Maps for more information.

Source
Map.scala
Graph
Supertypes
trait Map[K, V]
trait MapOps[K, V, Map, Map[K, V]]
trait Shrinkable[K]
trait Builder[(K, V), Map[K, V]]
trait Growable[(K, V)]
trait Clearable
trait Cloneable[Map[K, V]]
trait Cloneable
trait Map[K, V]
trait Equals
trait MapOps[K, V, Map, Map[K, V]]
trait PartialFunction[K, V]
trait K => V
trait Iterable[(K, V)]
trait Iterable[(K, V)]
trait IterableOps[(K, V), Iterable, Map[K, V]]
trait IterableOnceOps[(K, V), Iterable, Map[K, V]]
trait IterableOnce[(K, V)]
class Object
trait Matchable
class Any
Show all
Known subtypes
class TrieMap[K, V]

Members list

Value members

Abstract methods

def putIfAbsent(k: K, v: V): Option[V]

Associates the given key with a given value, unless the key was already associated with some other value.

Associates the given key with a given value, unless the key was already associated with some other value.

This is an atomic operation.

Value parameters

k

key with which the specified value is to be associated with

v

value to be associated with the specified key

Attributes

Returns

Some(oldvalue) if there was a value oldvalue previously associated with the specified key, or None if there was no mapping for the specified key

Source
Map.scala
def remove(k: K, v: V): Boolean

Removes the entry for the specified key if it's currently mapped to the specified value.

Removes the entry for the specified key if it's currently mapped to the specified value.

This is an atomic operation.

Value parameters

k

key for which the entry should be removed

v

value expected to be associated with the specified key if the removal is to take place

Attributes

Returns

true if the removal took place, false otherwise

Source
Map.scala
def replace(k: K, oldvalue: V, newvalue: V): Boolean

Replaces the entry for the given key only if it was previously mapped to a given value.

Replaces the entry for the given key only if it was previously mapped to a given value.

This is an atomic operation.

Value parameters

k

key for which the entry should be replaced

newvalue

value to be associated with the specified key

oldvalue

value expected to be associated with the specified key if replacing is to happen

Attributes

Returns

true if the entry was replaced, false otherwise

Source
Map.scala
def replace(k: K, v: V): Option[V]

Replaces the entry for the given key only if it was previously mapped to some value.

Replaces the entry for the given key only if it was previously mapped to some value.

This is an atomic operation.

Value parameters

k

key for which the entry should be replaced

v

value to be associated with the specified key

Attributes

Returns

Some(v) if the given key was previously mapped to some value v, or None otherwise

Source
Map.scala

Concrete methods

override def getOrElseUpdate(key: K, defaultValue: => V): V

If given key is already in this map, returns associated value.

If given key is already in this map, returns associated value.

Otherwise, computes value from given expression defaultValue, stores with key in map and returns that value.

Concurrent map implementations may evaluate the expression defaultValue multiple times, or may evaluate defaultValue without inserting the result.

Value parameters

defaultValue

the computation yielding the value to associate with key, if key is previously unbound.

key

the key to test

Attributes

Returns

the value associated with key (either previously or as a result of executing the method).

Definition Classes
Source
Map.scala
override def updateWith(key: K)(remappingFunction: Option[V] => Option[V]): Option[V]

Update a mapping for the specified key and its current optionally mapped value (Some if there is current mapping, None if not).

Update a mapping for the specified key and its current optionally mapped value (Some if there is current mapping, None if not).

If the remapping function returns Some(v), the mapping is updated with the new value v. If the remapping function returns None, the mapping is removed (or remains absent if initially absent). If the function itself throws an exception, the exception is rethrown, and the current mapping is left unchanged.

If the map is updated by another concurrent access, the remapping function will be retried until successfully updated.

Value parameters

key

the key value

remappingFunction

a function that receives current optionally mapped value and return a new mapping

Attributes

Returns

the new value associated with the specified key

Definition Classes
Source
Map.scala

Inherited methods

final def ++[B >: (K, V)](suffix: IterableOnce[B]): Iterable[B]

Alias for concat

Alias for concat

Attributes

Inherited from:
IterableOps
Source
Iterable.scala
def ++[V2 >: V](xs: IterableOnce[(K, V2)]): Map[K, V2]

Alias for concat

Alias for concat

Attributes

Inherited from:
MapOps
Source
Map.scala
final def ++=(elems: IterableOnce[(K, V)]): Growable.this.type

Alias for addAll

Alias for addAll

Attributes

Inherited from:
Growable
Source
Growable.scala
final def +=(elem: (K, V)): Growable.this.type

Alias for addOne

Alias for addOne

Attributes

Inherited from:
Growable
Source
Growable.scala
final def --=(xs: IterableOnce[K]): Shrinkable.this.type

Alias for subtractAll

Alias for subtractAll

Attributes

Inherited from:
Shrinkable
Source
Shrinkable.scala
final def -=(elem: K): Shrinkable.this.type

Alias for subtractOne

Alias for subtractOne

Attributes

Inherited from:
Shrinkable
Source
Shrinkable.scala
def addAll(elems: IterableOnce[(K, V)]): Growable.this.type

Adds all elements produced by an IterableOnce to this growable collection.

Adds all elements produced by an IterableOnce to this growable collection.

Value parameters

elems

the IterableOnce producing the elements to add.

Attributes

Returns

the growable collection itself.

Inherited from:
Growable
Source
Growable.scala
final def addString(b: StringBuilder): b.type

Appends all elements of this collection to a string builder.

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

Example:

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

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

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

Value parameters

b

the string builder to which elements are appended.

Attributes

Returns

the string builder b to which elements were appended.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
final def addString(b: StringBuilder, sep: String): b.type

Appends all elements of this collection to a string builder using a separator string.

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

Value parameters

b

the string builder to which elements are appended.

sep

the separator string.

Attributes

Returns

the string builder b to which elements were appended.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
override def addString(sb: StringBuilder, start: String, sep: String, end: String): sb.type

Appends all elements of this map to a string builder using start, end, and separator strings.

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)

Value parameters

b

the string builder to which elements are appended.

end

the ending string.

sep

the separator string.

start

the starting string.

Attributes

Returns

the string builder b to which elements were appended.

Definition Classes
Inherited from:
MapOps
Source
Map.scala
def andThen[C](k: PartialFunction[V, C]): PartialFunction[K, C]

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

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

Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. For efficiency, it is recommended to call applyOrElse instead of isDefinedAt or apply.

Type parameters

C

the result type of the transformation function.

Value parameters

k

the transformation function

Attributes

Returns

a partial function with the domain of this partial function narrowed by other partial function, which maps arguments x to k(this(x)).

Inherited from:
PartialFunction
Source
PartialFunction.scala
override def andThen[C](k: V => C): PartialFunction[K, C]

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

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

If the runtime type of the function is a PartialFunction then the other andThen method is used (note its cautions).

Type parameters

C

the result type of the transformation function.

Value parameters

k

the transformation function

Attributes

Returns

a partial function with the domain of this partial function, possibly narrowed by the specified function, which maps arguments x to k(this(x)).

Definition Classes
Inherited from:
PartialFunction
Source
PartialFunction.scala
def apply(key: K): V

Retrieves the value which is associated with the given key.

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.

Value parameters

key

the key

Attributes

Returns

the value associated with the given key, or the result of the map's default method, if none exists.

Inherited from:
MapOps
Source
Map.scala
override def applyOrElse[K1 <: K, V1 >: V](x: K1, default: K1 => V1): V1

Applies this partial function to the given argument when it is contained in the function domain.

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.

Value parameters

default

the fallback function

x

the function argument

Attributes

Returns

the result of this function or fallback function application.

Definition Classes
Inherited from:
MapOps
Source
Map.scala
def canEqual(that: Any): Boolean

Checks whether this instance can possibly equal that.

Checks whether this instance can possibly equal that.

A method that should be called from every well-designed equals method that is open to be overridden in a subclass. See Programming in Scala, Chapter 28 for discussion and design.

Value parameters

that

the value being probed for possible equality

Attributes

Returns

true if this instance can possibly equal that, otherwise false

Inherited from:
Map
Source
Map.scala
def clear(): Unit

Clears the contents of this builder.

Clears the contents of this builder. After execution of this method the builder will contain no elements.

Attributes

Inherited from:
MapOps
Source
Map.scala
override def clone(): Map[K, V]

Create a copy of the receiver object.

Create a copy of the receiver object.

The default implementation of the clone method is platform dependent.

Attributes

Returns

a copy of the receiver object.

Note

not specified by SLS as a member of AnyRef

Definition Classes
Inherited from:
MapOps
Source
Map.scala
def collect[B](pf: PartialFunction[(K, V), B]): Iterable[B]

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

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

Type parameters

B

the element type of the returned iterable collection.

Value parameters

pf

the partial function which filters and maps the iterable collection.

Attributes

Returns

a new iterable collection resulting from applying the given partial function pf to each element on which it is defined and collecting the results. The order of the elements is preserved.

Inherited from:
IterableOps
Source
Iterable.scala
def collect[K2, V2](pf: PartialFunction[(K, V), (K2, V2)]): Map[K2, V2]

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

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

Type parameters

K2

the key type of the returned map.

V2

the value type of the returned map.

Value parameters

pf

the partial function which filters and maps the map.

Attributes

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.

Inherited from:
MapOps
Source
Map.scala
def collectFirst[B](pf: PartialFunction[(K, V), B]): Option[B]

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

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

Note: may not terminate for infinite-sized collections.

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

Value parameters

pf

the partial function

Attributes

Returns

an option value containing pf applied to the first value for which it is defined, or None if none exists.

Example

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

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def compose[R](k: PartialFunction[R, K]): PartialFunction[R, V]

Composes another partial function k with this partial function so that this partial function gets applied to results of k.

Composes another partial function k with this partial function so that this partial function gets applied to results of k.

Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. For efficiency, it is recommended to call applyOrElse instead of isDefinedAt or apply.

Type parameters

R

the parameter type of the transformation function.

Value parameters

k

the transformation function

Attributes

Returns

a partial function with the domain of other partial function narrowed by this partial function, which maps arguments x to this(k(x)).

Inherited from:
PartialFunction
Source
PartialFunction.scala
def compose[A](g: A => K): A => V

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

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

Type parameters

A

the type to which function g can be applied

Value parameters

g

a function A => T1

Attributes

Returns

a new function f such that f(x) == apply(g(x))

Inherited from:
Function1
Source
Function1.scala
def concat[B >: (K, V)](suffix: IterableOnce[B]): Iterable[B]

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

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

Type parameters

B

the element type of the returned collection.

Value parameters

suffix

the iterable to append.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def concat[V2 >: V](suffix: IterableOnce[(K, V2)]): Map[K, V2]

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

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.

Value parameters

suffix

the iterable to append.

Attributes

Returns

a new map which contains all elements of this map followed by all elements of suffix.

Inherited from:
MapOps
Source
Map.scala
def contains(key: K): Boolean

Tests whether this map contains a binding for a key.

Tests whether this map contains a binding for a key.

Value parameters

key

the key

Attributes

Returns

true if there is a binding for key in this map, false otherwise.

Inherited from:
MapOps
Source
Map.scala
def copyToArray[B >: (K, V)](xs: Array[B], start: Int, len: Int): Int

Copy elements to an array, returning the number of elements written.

Copy elements to an array, returning the number of elements written.

Fills the given array xs starting at index start with at most len elements of this collection.

Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached, or len elements have been copied.

Type parameters

B

the type of the elements of the array.

Value parameters

len

the maximal number of elements to copy.

start

the starting index of xs.

xs

the array to fill.

Attributes

Returns

the number of elements written to the array

Note

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def copyToArray[B >: (K, V)](xs: Array[B], start: Int): Int

Copies elements to an array, returning the number of elements written.

Copies elements to an array, returning the number of elements written.

Fills the given array xs starting at index start with values of this collection.

Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.

Type parameters

B

the type of the elements of the array.

Value parameters

start

the starting index of xs.

xs

the array to fill.

Attributes

Returns

the number of elements written to the array

Note

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def copyToArray[B >: (K, V)](xs: Array[B]): Int

Copies elements to an array, returning the number of elements written.

Copies elements to an array, returning the number of elements written.

Fills the given array xs starting at index start with values of this collection.

Copying will stop once either all the elements of this collection have been copied, or the end of the array is reached.

Type parameters

B

the type of the elements of the array.

Value parameters

xs

the array to fill.

Attributes

Returns

the number of elements written to the array

Note

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def corresponds[B](that: IterableOnce[B])(p: ((K, V), B) => Boolean): Boolean

Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.

Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.

Note: will not terminate for infinite-sized collections.

Type parameters

B

the type of the elements of that

Value parameters

p

the test predicate, which relates elements from both collections

that

the other collection

Attributes

Returns

true if both collections have the same length and p(x, y) is true for all corresponding elements x of this iterator and y of that, otherwise false

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def count(p: ((K, V)) => Boolean): Int

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

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

Note: will not terminate for infinite-sized collections.

Value parameters

p

the predicate used to test elements.

Attributes

Returns

the number of elements satisfying the predicate p.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def default(key: K): V

Defines the default value computation for the map, returned when a key is not found.

Defines the default value computation for the map, returned when a key is not found.

The method implemented here throws an exception, but it may be overridden by subclasses.

Value parameters

key

the given key value for which a binding is missing.

Attributes

Throws

NoSuchElementException if no default value is defined

Inherited from:
MapOps
Source
Map.scala
def drop(n: Int): Map[K, V]

Selects all elements except the first n ones.

Selects all elements except the first n ones.

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

Value parameters

n

the number of elements to drop from this iterable collection.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def dropRight(n: Int): Map[K, V]

Selects all elements except last n ones.

Selects all elements except last n ones.

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

Value parameters

n

the number of elements to drop from this iterable collection.

Attributes

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. If n is negative, don't drop any elements.

Inherited from:
IterableOps
Source
Iterable.scala
def dropWhile(p: ((K, V)) => Boolean): Map[K, V]

Selects all elements except the longest prefix that satisfies a predicate.

Selects all elements except the longest prefix that satisfies a predicate.

The matching prefix starts with the first element of this iterable collection, and the element following the prefix is the first element that does not satisfy the predicate. The matching prefix may be empty, so that this method returns the entire iterable collection.

Example:

scala> List(1, 2, 3, 100, 4).dropWhile(n => n < 10)
val res0: List[Int] = List(100, 4)

scala> List(1, 2, 3, 100, 4).dropWhile(n => n == 0)
val res1: List[Int] = List(1, 2, 3, 100, 4)

Use span to obtain both the prefix and suffix. Use filterNot to drop all elements that satisfy the predicate.

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

Value parameters

p

The predicate used to test elements.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala

Returns an extractor object with a unapplySeq method, which extracts each element of a sequence data.

Returns an extractor object with a unapplySeq method, which extracts each element of a sequence data.

Attributes

Example

val firstChar: String => Option[Char] = _.headOption
Seq("foo", "bar", "baz") match {
  case firstChar.unlift.elementWise(c0, c1, c2) =>
    println(s"$c0, $c1, $c2") // Output: f, b, b
}
Inherited from:
PartialFunction
Source
PartialFunction.scala
override def empty: Map[K, V]

The empty iterable of the same type as this iterable

The empty iterable of the same type as this iterable

Attributes

Returns

an empty iterable of type C.

Definition Classes
Inherited from:
MapFactoryDefaults
Source
Iterable.scala
override def equals(o: Any): Boolean

Equality of maps is implemented using the lookup method get.

Equality of maps is implemented using the lookup method get. This method returns true if

  • the argument o is a Map,

  • the two maps have the same size, and

  • for every (key, value) pair in this map, other.get(key) == Some(value).

The implementation of equals checks the canEqual method, so subclasses of Map can narrow down the equality to specific map types. The Map implementations in the standard library can all be compared, their canEqual methods return true.

Note: The equals method only respects the equality laws (symmetry, transitivity) if the two maps use the same key equivalence function in their lookup operation. For example, the key equivalence operation in a scala.collection.immutable.TreeMap is defined by its ordering. Comparing a TreeMap with a HashMap leads to unexpected results if ordering.equiv(k1, k2) (used for lookup in TreeMap) is different from k1 == k2 (used for lookup in HashMap).

scala> import scala.collection.immutable._
scala> val ord: Ordering[String] = _ compareToIgnoreCase _

scala> TreeMap("A" -> 1)(ord) == HashMap("a" -> 1)
val res0: Boolean = false

scala> HashMap("a" -> 1) == TreeMap("A" -> 1)(ord)
val res1: Boolean = true

Value parameters

o

The map to which this map is compared

Attributes

Returns

true if the two maps are equal according to the description

Definition Classes
Map -> Equals -> Any
Inherited from:
Map
Source
Map.scala
def exists(p: ((K, V)) => Boolean): Boolean

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

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

Note: may not terminate for infinite-sized collections.

Value parameters

p

the predicate used to test elements.

Attributes

Returns

true if the given predicate p is satisfied by at least one element of this collection, otherwise false

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def filter(pred: ((K, V)) => Boolean): Map[K, V]

Selects all elements of this iterable collection which satisfy a predicate.

Selects all elements of this iterable collection which satisfy a predicate.

Value parameters

p

the predicate used to test elements.

Attributes

Returns

a new iterable collection consisting of all elements of this iterable collection that satisfy the given predicate p. The order of the elements is preserved.

Inherited from:
IterableOps
Source
Iterable.scala
def filterInPlace(p: (K, V) => Boolean): MapOps.this.type

Retains only those mappings for which the predicate p returns true.

Retains only those mappings for which the predicate p returns true.

Value parameters

p

The test predicate

Attributes

Inherited from:
MapOps
Source
Map.scala
def filterNot(pred: ((K, V)) => Boolean): Map[K, V]

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

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

Value parameters

pred

the predicate used to test elements.

Attributes

Returns

a new iterable collection consisting of all elements of this iterable collection that do not satisfy the given predicate pred. Their order may not be preserved.

Inherited from:
IterableOps
Source
Iterable.scala
def find(p: ((K, V)) => Boolean): Option[(K, V)]

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

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

Note: may not terminate for infinite-sized collections.

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

Value parameters

p

the predicate used to test elements.

Attributes

Returns

an option value containing the first element in the collection that satisfies p, or None if none exists.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def flatMap[B](f: ((K, V)) => IterableOnce[B]): Iterable[B]

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

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

For example:

def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+")

The type of the resulting collection is guided by the static type of iterable collection. This might cause unexpected results sometimes. For example:

// lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set
def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet)

// lettersOf will return a Set[Char], not a Seq
def lettersOf(words: Seq[String]) = words.toSet flatMap ((word: String) => word.toSeq)

// xs will be an Iterable[Int]
val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2)

// ys will be a Map[Int, Int]
val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)

Type parameters

B

the element type of the returned collection.

Value parameters

f

the function to apply to each element.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def flatMap[K2, V2](f: ((K, V)) => IterableOnce[(K2, V2)]): Map[K2, V2]

Builds a new map by applying a function to all elements of this map and using the elements of the resulting collections.

Builds a new map by applying a function to all elements of this map and using the elements of the resulting collections.

Value parameters

f

the function to apply to each element.

Attributes

Returns

a new map resulting from applying the given collection-valued function f to each element of this map and concatenating the results.

Inherited from:
MapOps
Source
Map.scala
def flatten[B](implicit asIterable: ((K, V)) => IterableOnce[B]): Iterable[B]

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

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

The resulting collection's type will be guided by the type of iterable collection. For example:

val xs = List(
           Set(1, 2, 3),
           Set(1, 2, 3)
         ).flatten
// xs == List(1, 2, 3, 1, 2, 3)

val ys = Set(
           List(1, 2, 3),
           List(3, 2, 1)
         ).flatten
// ys == Set(1, 2, 3)

Type parameters

B

the type of the elements of each iterable collection.

Value parameters

asIterable

an implicit conversion which asserts that the element type of this iterable collection is an Iterable.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def fold[A1 >: (K, V)](z: A1)(op: (A1, A1) => A1): A1

Applies the given binary operator op to the given initial value z and all elements of this collection.

Applies the given binary operator op to the given initial value z and all elements of this collection.

For each application of the operator, each operand is either an element of this collection, the initial value, or another such application of the operator.

The order of applications of the operator is unspecified and may be nondeterministic. Each element appears exactly once in the computation. The initial value may be used an arbitrary number of times, but at least once.

If this collection is ordered, then for any application of the operator, the element(s) appearing in the left operand will precede those in the right.

Note: might return different results for different runs, unless either of the following conditions is met: (1) the operator is associative, and the underlying collection type is ordered; or (2) the operator is associative and commutative. In either case, it is also necessary that the initial value be a neutral value for the operator, e.g. Nil for List concatenation or 1 for multiplication.

The default implementation in IterableOnce is equivalent to foldLeft but may be overridden for more efficient traversal orders.

Note: will not terminate for infinite-sized collections.

Type parameters

A1

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

Value parameters

op

A binary operator; must be associative for the result to always be the same across runs.

z

An initial value; may be used an arbitrary number of times in the computation of the result; must be a neutral value for op for the result to always be the same across runs.

Attributes

Returns

The result of applying op between all the elements and z, or z if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def foldLeft[B](z: B)(op: (B, (K, V)) => B): B

Applies the given binary operator op to the given initial value z and all elements of this collection, going left to right.

Applies the given binary operator op to the given initial value z and all elements of this collection, going left to right. Returns the initial value if this collection is empty.

"Going left to right" only makes sense if this collection is ordered: then if x1, x2, ..., xn are the elements of this collection, the result is op( op( ... op( op(z, x1), x2) ... ), xn).

If this collection is not ordered, then for each application of the operator, each right operand is an element. In addition, the leftmost operand is the initial value, and each other left operand is itself an application of the operator. The elements of this collection and the initial value all appear exactly once in the computation.

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the binary operator.

Value parameters

op

A binary operator.

z

An initial value.

Attributes

Returns

The result of applying op to z and all elements of this collection, going left to right. Returns z if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def foldRight[B](z: B)(op: ((K, V), B) => B): B

Applies the given binary operator op to all elements of this collection and the given initial value z, going right to left.

Applies the given binary operator op to all elements of this collection and the given initial value z, going right to left. Returns the initial value if this collection is empty.

"Going right to left" only makes sense if this collection is ordered: then if x1, x2, ..., xn are the elements of this collection, the result is op(x1, op(x2, op( ... op(xn, z) ... ))).

If this collection is not ordered, then for each application of the operator, each left operand is an element. In addition, the rightmost operand is the initial value, and each other right operand is itself an application of the operator. The elements of this collection and the initial value all appear exactly once in the computation.

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the binary operator.

Value parameters

op

A binary operator.

z

An initial value.

Attributes

Returns

The result of applying op to all elements of this collection and z, going right to left. Returns z if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def forall(p: ((K, V)) => Boolean): Boolean

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

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

Note: may not terminate for infinite-sized collections.

Value parameters

p

the predicate used to test elements.

Attributes

Returns

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

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def foreach[U](f: ((K, V)) => U): Unit

Applies f to each element for its side effects.

Applies f to each element for its side effects. Note: U parameter needed to help scalac's type inference.

Attributes

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def foreachEntry[U](f: (K, V) => U): Unit

Apply f to each key/value pair for its side effects Note: [U] parameter needed to help scalac's type inference.

Apply f to each key/value pair for its side effects Note: [U] parameter needed to help scalac's type inference.

Attributes

Inherited from:
MapOps
Source
Map.scala
override protected def fromSpecific(coll: IterableOnce[(K, V)]): Map[K, V]

Defines how to turn a given Iterable[A] into a collection of type C.

Defines how to turn a given Iterable[A] into a collection of type C.

This process can be done in a strict way or a non-strict way (ie. without evaluating the elements of the resulting collections). In other words, this methods defines the evaluation model of the collection.

Attributes

Note

When implementing a custom collection type and refining C to the new type, this method needs to be overridden (the compiler will issue an error otherwise). In the common case where C =:= CC[A], this can be done by mixing in the scala.collection.IterableFactoryDefaults trait, which implements the method using iterableFactory.

As witnessed by the @uncheckedVariance annotation, using this method might be unsound. However, as long as it is called with an Iterable[A] obtained from this collection (as it is the case in the implementations of operations where we use a View[A]), it is safe.

Definition Classes
Inherited from:
MapFactoryDefaults
Source
Iterable.scala
def getOrElse[V1 >: V](key: K, default: => V1): V1

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

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

Type parameters

V1

the result type of the default computation.

Value parameters

default

a computation that yields a default value in case no binding for key is found in the map.

key

the key.

Attributes

Returns

the value associated with key if it exists, otherwise the result of the default computation.

Inherited from:
MapOps
Source
Map.scala
def groupBy[K](f: ((K, V)) => K): Map[K, Map[K, V]]

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

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

Note: Even when applied to a view or a lazy collection it will always force the elements.

Type parameters

K

the type of keys returned by the discriminator function.

Value parameters

f

the discriminator function.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def groupMap[K, B](key: ((K, V)) => K)(f: ((K, V)) => B): Map[K, Iterable[B]]

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

Partitions this iterable collection into a map of iterable collections according to a discriminator function key. Each element in a group is transformed into a value of type B using the value function.

It is equivalent to groupBy(key).mapValues(_.map(f)), but more efficient.

case class User(name: String, age: Int)

def namesByAge(users: Seq[User]): Map[Int, Seq[String]] =
  users.groupMap(_.age)(_.name)

Note: Even when applied to a view or a lazy collection it will always force the elements.

Type parameters

B

the type of values returned by the transformation function

K

the type of keys returned by the discriminator function

Value parameters

f

the element transformation function

key

the discriminator function

Attributes

Inherited from:
IterableOps
Source
Iterable.scala
def groupMapReduce[K, B](key: ((K, V)) => K)(f: ((K, V)) => B)(reduce: (B, B) => B): Map[K, B]

Partitions this iterable collection into a map according to a discriminator function key.

Partitions this iterable collection into a map according to a discriminator function key. All the values that have the same discriminator are then transformed by the f function and then reduced into a single value with the reduce function.

It is equivalent to groupBy(key).mapValues(_.map(f).reduce(reduce)), but more efficient.

def occurrences[A](as: Seq[A]): Map[A, Int] =
  as.groupMapReduce(identity)(_ => 1)(_ + _)

Note: Even when applied to a view or a lazy collection it will always force the elements.

Attributes

Inherited from:
IterableOps
Source
Iterable.scala
def grouped(size: Int): Iterator[Map[K, V]]

Partitions elements in fixed size iterable collections.

Partitions elements in fixed size iterable collections.

Value parameters

size

the number of elements per group

Attributes

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.

See also

scala.collection.Iterator, method grouped

Inherited from:
IterableOps
Source
Iterable.scala
override def hashCode(): Int

Calculates a hash code value for the object.

Calculates a hash code value for the object.

The default hashing algorithm is platform dependent.

Note that it is allowed for two objects to have identical hash codes (o1.hashCode.equals(o2.hashCode)) yet not be equal (o1.equals(o2) returns false). A degenerate implementation could always return 0. However, it is required that if two objects are equal (o1.equals(o2) returns true) that they have identical hash codes (o1.hashCode.equals(o2.hashCode)). Therefore, when overriding this method, be sure to verify that the behavior is consistent with the equals method.

Attributes

Returns

the hash code value for this object.

Definition Classes
Map -> Any
Inherited from:
Map
Source
Map.scala
def head: (K, V)

Selects the first element of this iterable collection.

Selects the first element of this iterable collection.

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

Attributes

Returns

the first element of this iterable collection.

Throws

NoSuchElementException if the iterable collection is empty.

Inherited from:
IterableOps
Source
Iterable.scala
def headOption: Option[(K, V)]

Optionally selects the first element.

Optionally selects the first element.

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

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def init: Map[K, V]

The initial part of the collection without its last element.

The initial part of the collection without its last element.

Note: Even when applied to a view or a lazy collection it will always force the elements.

Attributes

Inherited from:
IterableOps
Source
Iterable.scala
def inits: Iterator[Map[K, V]]

Iterates over the inits of this iterable collection.

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

Note: Even when applied to a view or a lazy collection it will always force the elements.

Attributes

Returns

an iterator over all the inits of this iterable collection

Example

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

Inherited from:
IterableOps
Source
Iterable.scala
def isDefinedAt(key: K): Boolean

Tests whether this map contains a binding for a key.

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

Value parameters

key

the key

Attributes

Returns

true if there is a binding for key in this map, false otherwise.

Inherited from:
MapOps
Source
Map.scala

Tests whether the collection is empty.

Tests whether the collection is empty.

Note: The default implementation creates and discards an iterator.

Note: Implementations in subclasses that are not repeatedly iterable must take care not to consume any elements when isEmpty is called.

Attributes

Returns

true if the collection contains no elements, false otherwise.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
override def isTraversableAgain: Boolean

Tests whether this iterable collection can be repeatedly traversed.

Tests whether this iterable collection can be repeatedly traversed. Always true for Iterables and false for Iterators unless overridden.

Attributes

Returns

true if it is repeatedly traversable, false otherwise.

Definition Classes
Inherited from:
IterableOps
Source
Iterable.scala

The companion object of this iterable collection, providing various factory methods.

The companion object of this iterable collection, providing various factory methods.

Attributes

Note

When implementing a custom collection type and refining CC to the new type, this method needs to be overridden to return a factory for the new type (the compiler will issue an error otherwise).

Definition Classes
Inherited from:
Iterable
Source
Iterable.scala
def keySet: Set[K]

A set representing the keys contained by this map.

A set representing the keys contained by this map.

For efficiency the resulting set may be a view (maintaining a reference to the map and reflecting modifications to the map), but it may also be a strict collection without reference to the map.

  • To ensure an independent strict collection, use m.keysIterator.toSet

  • To obtain a view on the keys, use scala.collection.View.fromIteratorProvider(m.keysIterator)

Attributes

Returns

a set representing the keys contained by this map

Inherited from:
MapOps
Source
Map.scala
def keyStepper[S <: Stepper[_]](implicit shape: StepperShape[K, S]): S

Returns a Stepper for the keys of this map.

Returns a Stepper for the keys of this map. See method stepper.

Attributes

Inherited from:
MapOps
Source
Map.scala
def keys: Iterable[K]

An Iterable collection of the keys contained by this map.

An Iterable collection of the keys contained by this map.

For efficiency the resulting collection may be a view (maintaining a reference to the map and reflecting modifications to the map), but it may also be a strict collection without reference to the map.

  • To ensure an independent strict collection, use m.keysIterator.toSet

  • To obtain a view on the keys, use scala.collection.View.fromIteratorProvider(m.keysIterator)

Attributes

Returns

an Iterable collection of the keys contained by this map

Inherited from:
MapOps
Source
Map.scala

An Iterator of the keys contained by this map.

An Iterator of the keys contained by this map.

Attributes

Returns

an Iterator of the keys contained by this map

Inherited from:
MapOps
Source
Map.scala
override def knownSize: Int

The number of elements in the collection under construction, if it can be cheaply computed, -1 otherwise.

The number of elements in the collection under construction, if it can be cheaply computed, -1 otherwise.

Attributes

Returns

The number of elements. The default implementation always returns -1.

Definition Classes
Inherited from:
MapOps
Source
Map.scala
def last: (K, V)

Selects the last element.

Selects the last element.

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

Attributes

Returns

The last element of this iterable collection.

Throws

NoSuchElementException If the iterable collection is empty.

Inherited from:
IterableOps
Source
Iterable.scala
def lastOption: Option[(K, V)]

Optionally selects the last element.

Optionally selects the last element.

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

Attributes

Returns

the last element of this iterable collection$ if it is nonempty, None if it is empty.

Inherited from:
IterableOps
Source
Iterable.scala
def lazyZip[B](that: Iterable[B]): LazyZip2[(K, V), B, Iterable.this.type]

Analogous to zip except that the elements in each collection are not consumed until a strict operation is invoked on the returned LazyZip2 decorator.

Analogous to zip except that the elements in each collection are not consumed until a strict operation is invoked on the returned LazyZip2 decorator.

Calls to lazyZip can be chained to support higher arities (up to 4) without incurring the expense of constructing and deconstructing intermediary tuples.

val xs = List(1, 2, 3)
val res = (xs lazyZip xs lazyZip xs lazyZip xs).map((a, b, c, d) => a + b + c + d)
// res == List(4, 8, 12)

Type parameters

B

the type of the second element in each eventual pair

Value parameters

that

the iterable providing the second element of each eventual pair

Attributes

Returns

a decorator LazyZip2 that allows strict operations to be performed on the lazily evaluated pairs or chained calls to lazyZip. Implicit conversion to Iterable[(A, B)] is also supported.

Inherited from:
Iterable
Source
Iterable.scala
def lift: K => Option[V]

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

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

Attributes

Returns

a function that takes an argument x to Some(this(x)) if this is defined for x, and to None otherwise.

See also

Function.unlift

Inherited from:
PartialFunction
Source
PartialFunction.scala
def map[B](f: ((K, V)) => B): Iterable[B]

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

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

Type parameters

B

the element type of the returned iterable collection.

Value parameters

f

the function to apply to each element.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def map[K2, V2](f: ((K, V)) => (K2, V2)): Map[K2, V2]

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

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

Value parameters

f

the function to apply to each element.

Attributes

Returns

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

Inherited from:
MapOps
Source
Map.scala
override def mapFactory: MapFactory[Map]

The companion object of this map, providing various factory methods.

The companion object of this map, providing various factory methods.

Attributes

Note

When implementing a custom collection type and refining CC to the new type, this method needs to be overridden to return a factory for the new type (the compiler will issue an error otherwise).

Definition Classes
Map -> Map -> MapOps
Inherited from:
Map
Source
Map.scala
def mapResult[NewTo](f: Map[K, V] => NewTo): Builder[(K, V), NewTo]

A builder resulting from this builder my mapping the result using f.

A builder resulting from this builder my mapping the result using f.

Attributes

Inherited from:
Builder
Source
Builder.scala
def mapValuesInPlace(f: (K, V) => V): MapOps.this.type

Applies a transformation function to all values contained in this map.

Applies a transformation function to all values contained in this map. The transformation function produces new values from existing keys associated values.

Value parameters

f

the transformation to apply

Attributes

Returns

the map itself.

Inherited from:
MapOps
Source
Map.scala
def max[B >: (K, V)](implicit ord: Ordering[B]): (K, V)

Finds the largest element.

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B

The type over which the ordering is defined.

Value parameters

ord

An ordering to be used for comparing elements.

Attributes

Returns

the largest element of this collection with respect to the ordering ord.

Throws

UnsupportedOperationException if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def maxBy[B](f: ((K, V)) => B)(implicit ord: Ordering[B]): (K, V)

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the function f.

Value parameters

cmp

An ordering to be used for comparing elements.

f

The measuring function.

Attributes

Returns

the first element of this collection with the largest value measured by function f with respect to the ordering cmp.

Throws

UnsupportedOperationException if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def maxByOption[B](f: ((K, V)) => B)(implicit ord: Ordering[B]): Option[(K, V)]

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the function f.

Value parameters

cmp

An ordering to be used for comparing elements.

f

The measuring function.

Attributes

Returns

an option value containing the first element of this collection with the largest value measured by function f with respect to the ordering cmp.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def maxOption[B >: (K, V)](implicit ord: Ordering[B]): Option[(K, V)]

Finds the largest element.

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B

The type over which the ordering is defined.

Value parameters

ord

An ordering to be used for comparing elements.

Attributes

Returns

an option value containing the largest element of this collection with respect to the ordering ord.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def min[B >: (K, V)](implicit ord: Ordering[B]): (K, V)

Finds the smallest element.

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B

The type over which the ordering is defined.

Value parameters

ord

An ordering to be used for comparing elements.

Attributes

Returns

the smallest element of this collection with respect to the ordering ord.

Throws

UnsupportedOperationException if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def minBy[B](f: ((K, V)) => B)(implicit ord: Ordering[B]): (K, V)

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the function f.

Value parameters

cmp

An ordering to be used for comparing elements.

f

The measuring function.

Attributes

Returns

the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.

Throws

UnsupportedOperationException if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def minByOption[B](f: ((K, V)) => B)(implicit ord: Ordering[B]): Option[(K, V)]

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the function f.

Value parameters

cmp

An ordering to be used for comparing elements.

f

The measuring function.

Attributes

Returns

an option value containing the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def minOption[B >: (K, V)](implicit ord: Ordering[B]): Option[(K, V)]

Finds the smallest element.

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B

The type over which the ordering is defined.

Value parameters

ord

An ordering to be used for comparing elements.

Attributes

Returns

an option value containing the smallest element of this collection with respect to the ordering ord.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
final def mkString: String

Displays all elements of this collection in a string.

Displays all elements of this collection in a string.

Delegates to addString, which can be overridden.

Attributes

Returns

a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection follow each other without any separator string.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
final def mkString(sep: String): String

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

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

Delegates to addString, which can be overridden.

Value parameters

sep

the separator string.

Attributes

Returns

a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection are separated by the string sep.

Example

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

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
final def mkString(start: String, sep: String, end: String): String

Displays all elements of this collection in a string using start, end, and separator strings.

Displays all elements of this collection in a string using start, end, and separator strings.

Delegates to addString, which can be overridden.

Value parameters

end

the ending string.

sep

the separator string.

start

the starting string.

Attributes

Returns

a string representation of this 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 collection are separated by the string sep.

Example

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

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
override protected def newSpecificBuilder: Builder[(K, V), Map[K, V]]

Attributes

Returns

a strict builder for the same collection type. Note that in the case of lazy collections (e.g. scala.collection.View or scala.collection.immutable.LazyList), it is possible to implement this method but the resulting Builder will break laziness. As a consequence, operations should preferably be implemented with fromSpecific instead of this method.

Note

When implementing a custom collection type and refining C to the new type, this method needs to be overridden (the compiler will issue an error otherwise). In the common case where C =:= CC[A], this can be done by mixing in the scala.collection.IterableFactoryDefaults trait, which implements the method using iterableFactory.

As witnessed by the @uncheckedVariance annotation, using this method might be unsound. However, as long as the returned builder is only fed with A values taken from this instance, it is safe.

Definition Classes
Inherited from:
MapFactoryDefaults
Source
Iterable.scala

Tests whether the collection is not empty.

Tests whether the collection is not empty.

Attributes

Returns

true if the collection contains at least one element, false otherwise.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def orElse[A1 <: K, B1 >: V](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.

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

Type parameters

A1

the argument type of the fallback function

B1

the result type of the fallback function

Value parameters

that

the fallback function

Attributes

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.

Inherited from:
PartialFunction
Source
PartialFunction.scala
def partition(p: ((K, V)) => Boolean): (Map[K, V], Map[K, V])

A pair of, first, all elements that satisfy predicate p and, second, all elements that do not.

A pair of, first, all elements that satisfy predicate p and, second, all elements that do not. Interesting because it splits a collection in two.

The default implementation provided here needs to traverse the collection twice. Strict collections have an overridden version of partition in StrictOptimizedIterableOps, which requires only a single traversal.

Attributes

Inherited from:
IterableOps
Source
Iterable.scala
def partitionMap[A1, A2](f: ((K, V)) => Either[A1, A2]): (Iterable[A1], Iterable[A2])

Applies a function f to each element of the iterable collection and returns a pair of iterable collections: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.

Applies a function f to each element of the iterable collection and returns a pair of iterable collections: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.

Example:

val xs = Iterable(1, "one", 2, "two", 3, "three") partitionMap {
 case i: Int => Left(i)
 case s: String => Right(s)
}
// xs == (Iterable(1, 2, 3),
//        Iterable(one, two, three))

Type parameters

A1

the element type of the first resulting collection

A2

the element type of the second resulting collection

Value parameters

f

the 'split function' mapping the elements of this iterable collection to an scala.util.Either

Attributes

Returns

a pair of iterable collections: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.

Inherited from:
IterableOps
Source
Iterable.scala
def product[B >: (K, V)](implicit num: Numeric[B]): B

Multiplies together the elements of this collection.

Multiplies together the elements of this collection.

The default implementation uses reduce for a known non-empty collection, foldLeft otherwise.

Note: will not terminate for infinite-sized collections.

Type parameters

B

the result type of the * operator.

Value parameters

num

an implicit parameter defining a set of numeric operations which includes the * operator to be used in forming the product.

Attributes

Returns

the product of all elements of this collection with respect to the * operator in num.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def put(key: K, value: V): Option[V]

Adds a new key/value pair to this map and optionally returns previously bound value.

Adds a new key/value pair to this map and optionally returns previously bound value. If the map already contains a mapping for the key, it will be overridden by the new value.

Value parameters

key

the key to update

value

the new value

Attributes

Returns

an option value containing the value associated with the key before the put operation was executed, or None if key was not defined in the map before.

Inherited from:
MapOps
Source
Map.scala
def reduce[B >: (K, V)](op: (B, B) => B): B

Applies the given binary operator op to all elements of this collection.

Applies the given binary operator op to all elements of this collection.

For each application of the operator, each operand is either an element of this collection or another such application of the operator. The order of applications of the operator is unspecified and may be nondeterministic. Each element appears exactly once in the computation.

If this collection is ordered, then for any application of the operator, the element(s) appearing in the left operand will precede those in the right.

Note: might return different results for different runs, unless either of the following conditions is met: (1) the operator is associative, and the underlying collection type is ordered; or (2) the operator is associative and commutative.

Note: will not terminate for infinite-sized collections.

Type parameters

B

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

Value parameters

op

A binary operator; must be associative for the result to always be the same across runs.

Attributes

Returns

The result of applying op between all the elements if the collection is nonempty.

Throws

UnsupportedOperationException if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def reduceLeft[B >: (K, V)](op: (B, (K, V)) => B): B

Applies the given binary operator op to all elements of this collection, going left to right.

Applies the given binary operator op to all elements of this collection, going left to right.

"Going left to right" only makes sense if this collection is ordered: then if x1, x2, ..., xn are the elements of this collection, the result is op( op( op( ... op(x1, x2) ... ), xn-1), xn).

If this collection is not ordered, then for each application of the operator, each right operand is an element. In addition, the leftmost operand is the first element of this collection and each other left operand is itself an application of the operator. Each element appears exactly once in the computation.

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the binary operator, a supertype of A.

Value parameters

op

A binary operator.

Attributes

Returns

The result of applying op to all elements of this collection, going left to right.

Throws

UnsupportedOperationException if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def reduceLeftOption[B >: (K, V)](op: (B, (K, V)) => B): Option[B]

If this collection is nonempty, reduces it with the given binary operator op, going left to right.

If this collection is nonempty, reduces it with the given binary operator op, going left to right.

The behavior is the same as reduceLeft except that the value is None if the collection is empty. Each element appears exactly once in the computation.

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the binary operator, a supertype of A.

Value parameters

op

A binary operator.

Attributes

Returns

The result of reducing this collection with op going left to right if the collection is nonempty, inside a Some, and None otherwise.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def reduceOption[B >: (K, V)](op: (B, B) => B): Option[B]

If this collection is nonempty, reduces it with the given binary operator op.

If this collection is nonempty, reduces it with the given binary operator op.

The behavior is the same as reduce except that the value is None if the collection is empty. The order of applications of the operator is unspecified and may be nondeterministic. Each element appears exactly once in the computation.

Note: might return different results for different runs, unless either of the following conditions is met: (1) the operator is associative, and the underlying collection type is ordered; or (2) the operator is associative and commutative.

Note: will not terminate for infinite-sized collections.

Type parameters

B

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

Value parameters

op

A binary operator; must be associative for the result to always be the same across runs.

Attributes

Returns

The result of reducing this collection with op if the collection is nonempty, inside a Some, and None otherwise.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def reduceRight[B >: (K, V)](op: ((K, V), B) => B): B

Applies the given binary operator op to all elements of this collection, going right to left.

Applies the given binary operator op to all elements of this collection, going right to left.

"Going right to left" only makes sense if this collection is ordered: then if x1, x2, ..., xn are the elements of this collection, the result is op(x1, op(x2, op( ... op(xn-1, xn) ... ))).

If this collection is not ordered, then for each application of the operator, each left operand is an element. In addition, the rightmost operand is the last element of this collection and each other right operand is itself an application of the operator. Each element appears exactly once in the computation.

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the binary operator, a supertype of A.

Value parameters

op

A binary operator.

Attributes

Returns

The result of applying op to all elements of this collection, going right to left.

Throws

UnsupportedOperationException if this collection is empty.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def reduceRightOption[B >: (K, V)](op: ((K, V), B) => B): Option[B]

If this collection is nonempty, reduces it with the given binary operator op, going right to left.

If this collection is nonempty, reduces it with the given binary operator op, going right to left.

The behavior is the same as reduceRight except that the value is None if the collection is empty. Each element appears exactly once in the computation.

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

Note: will not terminate for infinite-sized collections.

Type parameters

B

The result type of the binary operator, a supertype of A.

Value parameters

op

A binary operator.

Attributes

Returns

The result of reducing this collection with op going right to left if the collection is nonempty, inside a Some, and None otherwise.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def remove(key: K): Option[V]

Removes a key from this map, returning the value associated previously with that key as an option.

Removes a key from this map, returning the value associated previously with that key as an option.

Value parameters

key

the key to be removed

Attributes

Returns

an option value containing the value associated previously with key, or None if key was not defined in the map before.

Inherited from:
MapOps
Source
Map.scala
def result(): Map[K, V]

Result collection consisting of all elements appended so far.

Result collection consisting of all elements appended so far.

Attributes

Inherited from:
MapOps
Source
Map.scala
protected def reversed: Iterable[(K, V)]

Attributes

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def runWith[U](action: V => U): K => Boolean

Composes this partial function with an action function which gets applied to results of this partial function.

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.

Value parameters

action

the action function

Attributes

Returns

a function which maps arguments x to isDefinedAt(x). The resulting function runs action(this(x)) where this is defined.

See also

applyOrElse.

Inherited from:
PartialFunction
Source
PartialFunction.scala
def scan[B >: (K, V)](z: B)(op: (B, B) => B): Iterable[B]

Computes a prefix scan of the elements of the collection.

Computes a prefix scan of the elements of the collection.

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

Type parameters

B

element type of the resulting collection

Value parameters

op

the associative operator for the scan

z

neutral element for the operator op

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def scanLeft[B](z: B)(op: (B, (K, V)) => B): Iterable[B]

Produces a iterable collection containing cumulative results of applying the operator going left to right, including the initial value.

Produces a iterable collection containing cumulative results of applying the operator going left to right, including the initial value.

Note: will not terminate for infinite-sized collections.

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

Type parameters

B

the type of the elements in the resulting collection

Value parameters

op

the binary operator applied to the intermediate result and the element

z

the initial value

Attributes

Returns

collection with intermediate results

Inherited from:
IterableOps
Source
Iterable.scala
def scanRight[B](z: B)(op: ((K, V), B) => B): Iterable[B]

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

Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result.

Note: will not terminate for infinite-sized collections.

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

Note: Even when applied to a view or a lazy collection it will always force the elements.

Example:

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

Type parameters

B

the type of the elements in the resulting collection

Value parameters

op

the binary operator applied to the intermediate result and the element

z

the initial value

Attributes

Returns

collection with intermediate results

Inherited from:
IterableOps
Source
Iterable.scala
def size: Int

The size of this collection.

The size of this collection.

Note: will not terminate for infinite-sized collections.

Attributes

Returns

the number of elements in this collection.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def sizeCompare(that: Iterable[_]): Int

Compares the size of this iterable collection to the size of another Iterable.

Compares the size of this iterable collection to the size of another Iterable.

Value parameters

that

the Iterable whose size is compared with this iterable collection's size.

Attributes

Returns

A value x where

x <  0       if this.size <  that.size
x == 0       if this.size == that.size
x >  0       if this.size >  that.size

The method as implemented here does not call size directly; its running time is O(this.size min that.size) instead of O(this.size + that.size). The method should be overridden if computing size is cheap and knownSize returns -1.

Inherited from:
IterableOps
Source
Iterable.scala
def sizeCompare(otherSize: Int): Int

Compares the size of this iterable collection to a test value.

Compares the size of this iterable collection to a test value.

Value parameters

otherSize

the test value that gets compared with the size.

Attributes

Returns

A value x where

x <  0       if this.size <  otherSize
x == 0       if this.size == otherSize
x >  0       if this.size >  otherSize

The method as implemented here does not call size directly; its running time is O(size min otherSize) instead of O(size). The method should be overridden if computing size is cheap and knownSize returns -1.

See also
Inherited from:
IterableOps
Source
Iterable.scala
final def sizeHint(coll: IterableOnce[_], delta: Int): Unit

Gives a hint that the result of this builder is expected to have the same size as the given collection, plus some delta.

Gives a hint that the result of this builder is expected to have the same size as the given collection, plus some delta.

This method provides a hint only if the collection has a known size, as specified by the following pseudocode:

if (coll.knownSize != -1)
  if (coll.knownSize + delta <= 0) sizeHint(0)
  else sizeHint(coll.knownSize + delta)

If the delta is negative and the result size is known to be negative, then the size hint is issued at zero.

Some builder classes will optimize their representation based on the hint. However, builder implementations are required to work correctly even if the hint is wrong, i.e., if a different number of elements is added.

Value parameters

coll

the collection which serves as a hint for the result's size.

delta

a correction to add to the coll.size to produce the size hint (zero if omitted).

Attributes

Inherited from:
Builder
Source
Builder.scala
def sizeHint(size: Int): Unit

Gives a hint how many elements are expected to be added in total by the time result is called.

Gives a hint how many elements are expected to be added in total by the time result is called.

Some builder classes will optimize their representation based on the hint. However, builder implementations are required to work correctly even if the hint is wrong, e.g., a different number of elements is added, or the hint is out of range.

The default implementation simply ignores the hint.

Value parameters

size

the hint how many elements will be added.

Attributes

Inherited from:
Builder
Source
Builder.scala
final def sizeHintBounded(size: Int, boundingColl: Iterable[_]): Unit

Gives a hint how many elements are expected to be added when the next result is called, together with an upper bound given by the size of some other collection.

Gives a hint how many elements are expected to be added when the next result is called, together with an upper bound given by the size of some other collection. Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.

Value parameters

boundingColl

the bounding collection. If it is an IndexedSeqLike, then sizes larger than collection's size are reduced.

size

the hint how many elements will be added.

Attributes

Inherited from:
Builder
Source
Builder.scala
final def sizeIs: SizeCompareOps

Returns a value class containing operations for comparing the size of this iterable collection to a test value.

Returns a value class containing operations for comparing the size of this iterable collection to a test value.

These operations are implemented in terms of sizeCompare(Int), and allow the following more readable usages:

this.sizeIs < size     // this.sizeCompare(size) < 0
this.sizeIs <= size    // this.sizeCompare(size) <= 0
this.sizeIs == size    // this.sizeCompare(size) == 0
this.sizeIs != size    // this.sizeCompare(size) != 0
this.sizeIs >= size    // this.sizeCompare(size) >= 0
this.sizeIs > size     // this.sizeCompare(size) > 0

Attributes

Inherited from:
IterableOps
Source
Iterable.scala
def slice(from: Int, until: Int): Map[K, V]

Selects an interval of elements.

Selects an interval of elements. The returned iterable 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.

Value parameters

from

the lowest index to include from this iterable collection.

until

the lowest index to EXCLUDE from this iterable collection.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def sliding(size: Int, step: Int): Iterator[Map[K, V]]

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

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

The returned iterator will be empty when called on an empty collection. The last element the iterator produces may be smaller than the window size when the original collection isn't exhausted by the window before it and its last element isn't skipped by the step before it.

Value parameters

size

the number of elements per group

step

the distance between the first elements of successive groups

Attributes

Returns

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

See also

scala.collection.Iterator, method sliding

Example

List(1, 2, 3, 4, 5).sliding(2, 2) = Iterator(List(1, 2), List(3, 4), List(5))

List(1, 2, 3, 4, 5, 6).sliding(2, 3) = Iterator(List(1, 2), List(4, 5))

Inherited from:
IterableOps
Source
Iterable.scala
def sliding(size: Int): Iterator[Map[K, V]]

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

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

An empty collection returns an empty iterator, and a non-empty collection containing fewer elements than the window size returns an iterator that will produce the original collection as its only element.

Value parameters

size

the number of elements per group

Attributes

Returns

An iterator producing iterable collections of size size, except for a non-empty collection with less than size elements, which returns an iterator that produces the source collection itself as its only element.

See also

scala.collection.Iterator, method sliding

Example

List().sliding(2) = empty iterator

List(1).sliding(2) = Iterator(List(1))

List(1, 2).sliding(2) = Iterator(List(1, 2))

List(1, 2, 3).sliding(2) = Iterator(List(1, 2), List(2, 3))

Inherited from:
IterableOps
Source
Iterable.scala
def span(p: ((K, V)) => Boolean): (Map[K, V], Map[K, V])

Splits this iterable collection into a prefix/suffix pair according to a predicate.

Splits this iterable 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.

Value parameters

p

the test predicate

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
override def splitAt(n: Int): (Map[K, V], Map[K, V])

Splits this iterable collection into a prefix/suffix pair at a given position.

Splits this iterable collection into a prefix/suffix pair at a given position.

Note: c splitAt n is equivalent to (but possibly more efficient than) (c take n, c drop n).

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

Value parameters

n

the position at which to split.

Attributes

Returns

a pair of iterable collections consisting of the first n elements of this iterable collection, and the other elements.

Definition Classes
Inherited from:
IterableOps
Source
Iterable.scala
def stepper[S <: Stepper[_]](implicit shape: StepperShape[(K, V), S]): S

Returns a scala.collection.Stepper for the elements of this collection.

Returns a scala.collection.Stepper for the elements of this collection.

The Stepper enables creating a Java stream to operate on the collection, see scala.jdk.StreamConverters. For collections holding primitive values, the Stepper can be used as an iterator which doesn't box the elements.

The implicit scala.collection.StepperShape parameter defines the resulting Stepper type according to the element type of this collection.

Note that this method is overridden in subclasses and the return type is refined to S with EfficientSplit, for example scala.collection.IndexedSeqOps.stepper. For Steppers marked with scala.collection.Stepper.EfficientSplit, the converters in scala.jdk.StreamConverters allow creating parallel streams, whereas bare Steppers can be converted only to sequential streams.

Attributes

Inherited from:
IterableOnce
Source
IterableOnce.scala
def subtractAll(xs: IterableOnce[K]): Shrinkable.this.type

Removes all elements produced by an iterator from this shrinkable collection.

Removes all elements produced by an iterator from this shrinkable collection.

Value parameters

xs

the iterator producing the elements to remove.

Attributes

Returns

the shrinkable collection itself

Inherited from:
Shrinkable
Source
Shrinkable.scala
def sum[B >: (K, V)](implicit num: Numeric[B]): B

Sums the elements of this collection.

Sums the elements of this collection.

The default implementation uses reduce for a known non-empty collection, foldLeft otherwise.

Note: will not terminate for infinite-sized collections.

Type parameters

B

the result type of the + operator.

Value parameters

num

an implicit parameter defining a set of numeric operations which includes the + operator to be used in forming the sum.

Attributes

Returns

the sum of all elements of this collection with respect to the + operator in num.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def tail: Map[K, V]

The rest of the collection without its first element.

The rest of the collection without its first element.

Attributes

Inherited from:
IterableOps
Source
Iterable.scala
def tails: Iterator[Map[K, V]]

Iterates over the tails of this iterable collection.

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

Attributes

Returns

an iterator over all the tails of this iterable collection

Example

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

Inherited from:
IterableOps
Source
Iterable.scala
def take(n: Int): Map[K, V]

Selects the first n elements.

Selects the first n elements.

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

Value parameters

n

the number of elements to take from this iterable collection.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def takeRight(n: Int): Map[K, V]

Selects the last n elements.

Selects the last n elements.

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

Value parameters

n

the number of elements to take from this iterable collection.

Attributes

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. If n is negative, returns an empty iterable collection.

Inherited from:
IterableOps
Source
Iterable.scala
def takeWhile(p: ((K, V)) => Boolean): Map[K, V]

Takes longest prefix of elements that satisfy a predicate.

Takes longest prefix of elements that satisfy a predicate.

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

Value parameters

p

The predicate used to test elements.

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
override def tapEach[U](f: ((K, V)) => U): Map[K, V]

Applies a side-effecting function to each element in this collection.

Applies a side-effecting function to each element in this collection. Strict collections will apply f to their elements immediately, while lazy collections like Views and LazyLists will only apply f on each element if and when that element is evaluated, and each time that element is evaluated.

Type parameters

U

the return type of f

Value parameters

f

a function to apply to each element in this iterable collection

Attributes

Returns

The same logical collection as this

Definition Classes
Inherited from:
IterableOps
Source
Iterable.scala
def to[C1](factory: Factory[(K, V), C1]): C1

Given a collection factory factory, converts this collection to the appropriate representation for the current element type A.

Given a collection factory factory, converts this collection to the appropriate representation for the current element type A. Example uses:

xs.to(List)
xs.to(ArrayBuffer)
xs.to(BitSet) // for xs: Iterable[Int]

Attributes

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def toArray[B >: (K, V) : ClassTag]: Array[B]

Converts this collection to an Array.

Converts this collection to an Array.

Implementation note: DO NOT call Array.from from this method.

Type parameters

B

The type of elements of the result, a supertype of A.

Attributes

Returns

This collection as an Array[B].

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
final def toBuffer[B >: (K, V)]: Buffer[B]

Converts this collection to a Buffer.

Converts this collection to a Buffer.

Type parameters

B

The type of elements of the result, a supertype of A.

Attributes

Returns

This collection as a Buffer[B].

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def toIndexedSeq: IndexedSeq[(K, V)]

Converts this collection to an IndexedSeq.

Converts this collection to an IndexedSeq.

Attributes

Returns

This collection as an IndexedSeq[A].

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def toList: List[(K, V)]

Converts this collection to a List.

Converts this collection to a List.

Attributes

Returns

This collection as a List[A].

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def toMap[K, V](implicit ev: (K, V) <:< (K, V)): Map[K, V]

Converts this collection to a Map, given an implicit coercion from the collection's type to a key-value tuple.

Converts this collection to a Map, given an implicit coercion from the collection's type to a key-value tuple.

Type parameters

K

The key type for the resulting map.

V

The value type for the resulting map.

Value parameters

ev

An implicit coercion from A to [K, V].

Attributes

Returns

This collection as a Map[K, V].

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def toSeq: Seq[(K, V)]

Attributes

Returns

This collection as a Seq[A]. This is equivalent to to(Seq) but might be faster.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def toSet[B >: (K, V)]: Set[B]

Converts this collection to a Set.

Converts this collection to a Set.

Type parameters

B

The type of elements of the result, a supertype of A.

Attributes

Returns

This collection as a Set[B].

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
override def toString(): String

Returns a string representation of the object.

Returns a string representation of the object.

The default representation is platform dependent.

Attributes

Returns

a string representation of the object.

Definition Classes
Inherited from:
Map
Source
Map.scala
def toVector: Vector[(K, V)]

Converts this collection to a Vector.

Converts this collection to a Vector.

Attributes

Returns

This collection as a Vector[A].

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def transpose[B](implicit asIterable: ((K, V)) => Iterable[B]): Iterable[Iterable[B]]

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

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

The resulting collection's type will be guided by the static type of iterable collection. For example:

val xs = List(
           Set(1, 2, 3),
           Set(4, 5, 6)).transpose
// xs == List(
//         List(1, 4),
//         List(2, 5),
//         List(3, 6))

val ys = Vector(
           List(1, 2, 3),
           List(4, 5, 6)).transpose
// ys == Vector(
//         Vector(1, 4),
//         Vector(2, 5),
//         Vector(3, 6))

Note: Even when applied to a view or a lazy collection it will always force the elements.

Type parameters

B

the type of the elements of each iterable collection.

Value parameters

asIterable

an implicit conversion which asserts that the element type of this iterable collection is an Iterable.

Attributes

Returns

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

Throws

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

Inherited from:
IterableOps
Source
Iterable.scala
def unapply(a: K): Option[V]

Tries to extract a B from an A in a pattern matching expression.

Tries to extract a B from an A in a pattern matching expression.

Attributes

Inherited from:
PartialFunction
Source
PartialFunction.scala
def unzip[A1, A2](implicit asPair: ((K, V)) => (A1, A2)): (Iterable[A1], Iterable[A2])

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

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

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

Type parameters

A1

the type of the first half of the element pairs

A2

the type of the second half of the element pairs

Value parameters

asPair

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

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def unzip3[A1, A2, A3](implicit asTriple: ((K, V)) => (A1, A2, A3)): (Iterable[A1], Iterable[A2], Iterable[A3])

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

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

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

Type parameters

A1

the type of the first member of the element triples

A2

the type of the second member of the element triples

A3

the type of the third member of the element triples

Value parameters

asTriple

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

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def update(key: K, value: V): Unit

Adds a new key/value pair to this map.

Adds a new key/value pair to this map. If the map already contains a mapping for the key, it will be overridden by the new value.

Value parameters

key

The key to update

value

The new value

Attributes

Inherited from:
MapOps
Source
Map.scala
def valueStepper[S <: Stepper[_]](implicit shape: StepperShape[V, S]): S

Returns a Stepper for the values of this map.

Returns a Stepper for the values of this map. See method stepper.

Attributes

Inherited from:
MapOps
Source
Map.scala
def values: Iterable[V]

Collects all values of this map in an iterable collection.

Collects all values of this map in an iterable collection.

Attributes

Returns

the values of this map as an iterable.

Inherited from:
MapOps
Source
Map.scala

Creates an iterator for all values in this map.

Creates an iterator for all values in this map.

Attributes

Returns

an iterator over all values that are associated with some key in this map.

Inherited from:
MapOps
Source
Map.scala
override def view: MapView[K, V]

A view over the elements of this collection.

A view over the elements of this collection.

Attributes

Definition Classes
Inherited from:
MapOps
Source
Map.scala
def withDefault(d: K => V): Map[K, V]

The same map with a given default function.

The same map with a given default function. Note: The default is only used for apply. Other methods like get, contains, iterator, keys, etc. are not affected by withDefaultValue.

Invoking transformer methods (e.g. map) will not preserve the default value.

Value parameters

d

the function mapping keys to values, used for non-present keys

Attributes

Returns

a wrapper of the map with a default value

Inherited from:
Map
Source
Map.scala
def withDefaultValue(d: V): Map[K, V]

The same map with a given default value.

The same map with a given default value. Note: The default is only used for apply. Other methods like get, contains, iterator, keys, etc. are not affected by withDefaultValue.

Invoking transformer methods (e.g. map) will not preserve the default value.

Value parameters

d

default value used for non-present keys

Attributes

Returns

a wrapper of the map with a default value

Inherited from:
Map
Source
Map.scala
override def withFilter(p: ((K, V)) => Boolean): WithFilter[K, V, Iterable, Map]

Creates a non-strict filter of this map.

Creates a non-strict filter of this map.

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.

Value parameters

p

the predicate used to test elements.

Attributes

Returns

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

Definition Classes
Inherited from:
MapFactoryDefaults
Source
Iterable.scala
def zip[B](that: IterableOnce[B]): Iterable[((K, V), B)]

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

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

Type parameters

B

the type of the second half of the returned pairs

Value parameters

that

The iterable providing the second half of each result pair

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def zipAll[A1 >: (K, V), B](that: Iterable[B], thisElem: A1, thatElem: B): Iterable[(A1, B)]

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

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

Value parameters

that

the iterable providing the second half of each result pair

thatElem

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

thisElem

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

Attributes

Returns

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

Inherited from:
IterableOps
Source
Iterable.scala
def zipWithIndex: Iterable[((K, V), Int)]

Zips this iterable collection with its indices.

Zips this iterable collection with its indices.

Attributes

Returns

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

Example

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

Inherited from:
IterableOps
Source
Iterable.scala

Inherited and Abstract methods

def addOne(elem: (K, V)): Growable.this.type

Adds a single element to this growable collection.

Adds a single element to this growable collection.

Value parameters

elem

the element to add.

Attributes

Returns

the growable collection itself

Inherited from:
Growable
Source
Growable.scala
def get(key: K): Option[V]

Optionally returns the value associated with a key.

Optionally returns the value associated with a key.

Value parameters

key

the key value

Attributes

Returns

an option value containing the value associated with key in this map, or None if none exists.

Inherited from:
MapOps
Source
Map.scala
def iterator: Iterator[(K, V)]

An scala.collection.Iterator over the elements of this collection.

An scala.collection.Iterator over the elements of this collection.

If an IterableOnce object is in fact an scala.collection.Iterator, this method always returns itself, in its current state, but if it is an scala.collection.Iterable, this method always returns a new scala.collection.Iterator.

Attributes

Inherited from:
IterableOnce
Source
IterableOnce.scala
def subtractOne(elem: K): Shrinkable.this.type

Removes a single element from this shrinkable collection.

Removes a single element from this shrinkable collection.

Value parameters

elem

the element to remove.

Attributes

Returns

the shrinkable collection itself

Inherited from:
Shrinkable
Source
Shrinkable.scala

Deprecated and Inherited methods

def +[V1 >: V](elem1: (K, V1), elem2: (K, V1), elems: (K, V1)*): Map[K, V1]

Attributes

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
def +[V1 >: V](kv: (K, V1)): Map[K, V1]

Attributes

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
def ++:[B >: (K, V)](that: IterableOnce[B]): Iterable[B]

Attributes

Deprecated
true
Inherited from:
IterableOps
Source
Iterable.scala
def ++:[V1 >: V](that: IterableOnce[(K, V1)]): Map[K, V1]

Attributes

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
final def +=(elem1: (K, V), elem2: (K, V), elems: (K, V)*): Growable.this.type

Adds two or more elements to this growable collection.

Adds two or more elements to this growable collection.

Value parameters

elem1

the first element to add.

elem2

the second element to add.

elems

the remaining elements to add.

Attributes

Returns

the growable collection itself

Deprecated
true
Inherited from:
Growable
Source
Growable.scala
final def -(key1: K, key2: K, keys: K*): Map[K, V]

Attributes

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
final def -(key: K): Map[K, V]

Attributes

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
def --(keys: IterableOnce[K]): Map[K, V]

Attributes

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
def -=(elem1: K, elem2: K, elems: K*): Shrinkable.this.type

Removes two or more elements from this shrinkable collection.

Removes two or more elements from this shrinkable collection.

Value parameters

elem1

the first element to remove.

elem2

the second element to remove.

elems

the remaining elements to remove.

Attributes

Returns

the shrinkable collection itself

Deprecated
true
Inherited from:
Shrinkable
Source
Shrinkable.scala
final def /:[B](z: B)(op: (B, (K, V)) => B): B

Attributes

Deprecated
true
Inherited from:
IterableOnceOps
Source
IterableOnce.scala
final def :\[B](z: B)(op: ((K, V), B) => B): B

Attributes

Deprecated
true
Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def aggregate[B](z: => B)(seqop: (B, (K, V)) => B, combop: (B, B) => B): B

Aggregates the results of applying an operator to subsequent elements.

Aggregates the results of applying an operator to subsequent elements.

Since this method degenerates to foldLeft for sequential (non-parallel) collections, where the combining operation is ignored, it is advisable to prefer foldLeft for that case.

For parallel collections, use the aggregate method specified by scala.collection.parallel.ParIterableLike.

Type parameters

B

the result type, produced by seqop, combop, and by this function as a final result.

Value parameters

combop

an associative operator for combining sequential results, unused for sequential collections.

seqop

the binary operator used to accumulate the result.

z

the start value, a neutral element for seqop.

Attributes

Deprecated
true
Inherited from:
IterableOnceOps
Source
IterableOnce.scala

Attributes

Deprecated
true
Inherited from:
IterableOps
Source
Iterable.scala
final def copyToBuffer[B >: (K, V)](dest: Buffer[B]): Unit

Attributes

Deprecated
true
Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def filterKeys(p: K => Boolean): MapView[K, V]

Filters this map by retaining only keys satisfying a predicate.

Filters this map by retaining only keys satisfying a predicate.

Value parameters

p

the predicate used to test keys

Attributes

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.

Deprecated
true
Inherited from:
MapOps
Source
Map.scala

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

Tests whether this collection is known to have a finite size. All strict collections are known to have finite size. For a non-strict collection such as Stream, the predicate returns true if all elements have been computed. It returns false if the stream is not yet evaluated to the end. Non-empty Iterators usually return false even if they were created from a collection with a known finite size.

Note: many collection methods will not work on collections of infinite sizes. The typical failure mode is an infinite loop. These methods always attempt a traversal without checking first that hasDefiniteSize returns true. However, checking hasDefiniteSize can provide an assurance that size is well-defined and non-termination is not a concern.

Attributes

Returns

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

See also

method knownSize for a more useful alternative

Deprecated

This method is deprecated in 2.13 because it does not provide any actionable information. As noted above, even the collection library itself does not use it. When there is no guarantee that a collection is finite, it is generally best to attempt a computation anyway and document that it will not terminate for infinite collections rather than backing out because this would prevent performing the computation on collections that are in fact finite even though hasDefiniteSize returns false.

Inherited from:
IterableOnceOps
Source
IterableOnce.scala
def mapValues[W](f: V => W): MapView[K, W]

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

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

Value parameters

f

the function used to transform values of this map.

Attributes

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.

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
final def repr: Map[K, V]

Attributes

Deprecated
true
Inherited from:
IterableOps
Source
Iterable.scala
final def retain(p: (K, V) => Boolean): MapOps.this.type

Attributes

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
def seq: Iterable.this.type

Attributes

Deprecated
true
Inherited from:
Iterable
Source
Iterable.scala
final def toIterable: Iterable.this.type

Attributes

Returns

This collection as an Iterable[A]. No new collection will be built if this is already an Iterable[A].

Deprecated
true
Inherited from:
Iterable
Source
Iterable.scala
final def toIterator: Iterator[(K, V)]

Attributes

Deprecated
true
Inherited from:
IterableOnceOps
Source
IterableOnce.scala
final def toStream: Stream[(K, V)]

Attributes

Deprecated
true
Inherited from:
IterableOnceOps
Source
IterableOnce.scala
final def toTraversable: Iterable[(K, V)]

Converts this iterable collection to an unspecified Iterable.

Converts this iterable collection to an unspecified Iterable. Will return the same collection if this instance is already Iterable.

Attributes

Returns

An Iterable containing all elements of this iterable collection.

Deprecated
true
Inherited from:
IterableOps
Source
Iterable.scala
final def transform(f: (K, V) => V): MapOps.this.type

Attributes

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
def updated[V1 >: V](key: K, value: V1): Map[K, V1]

Attributes

Deprecated
true
Inherited from:
MapOps
Source
Map.scala
def view(from: Int, until: Int): View[(K, V)]

A view over a slice of the elements of this collection.

A view over a slice of the elements of this collection.

Attributes

Deprecated
true
Inherited from:
IterableOps
Source
Iterable.scala