# MultiMap

#### trait MultiMap[A, B] extends Map[A, Set[B]]

A trait for mutable maps with multiple values assigned to a key.

This class is typically used as a mixin. It turns maps which map `A` to `Set[B]` objects into multimaps that map `A` to `B` objects.

Source
MultiMap.scala
Example:
1. ```// first import all necessary types from package `collection.mutable`
import collection.mutable.{ HashMap, MultiMap, Set }

// to create a `MultiMap` the easiest way is to mixin it into a normal
// `Map` instance
val mm = new HashMap[Int, Set[String]] with MultiMap[Int, String]

// to add key-value pairs to a multimap it is important to use
// the method `addBinding` because standard methods like `+` will
// overwrite the complete key-value pair instead of adding the
// value to the existing key
mm.addBinding(1, "a")
mm.addBinding(2, "b")
mm.addBinding(1, "c")

// mm now contains `Map(2 -> Set(b), 1 -> Set(c, a))`

// to check if the multimap contains a value there is method
// `entryExists`, which allows to traverse the including set
mm.entryExists(1, _ == "a") == true
mm.entryExists(1, _ == "b") == false
mm.entryExists(2, _ == "b") == true

// to remove a previous added value there is the method `removeBinding`
mm.removeBinding(1, "a")
mm.entryExists(1, _ == "a") == false```
Linear Supertypes
Map[A, Set[B]], MapLike[A, Set[B], Map[A, Set[B]]], Cloneable[Map[A, Set[B]]], scala.Cloneable, java.lang.Cloneable, Shrinkable[A], Builder[(A, Set[B]), Map[A, Set[B]]], Growable[(A, Set[B])], Clearable, collection.Map[A, Set[B]], collection.MapLike[A, Set[B], Map[A, Set[B]]], Subtractable[A, Map[A, Set[B]]], PartialFunction[A, Set[B]], (A) ⇒ Set[B], GenMap[A, Set[B]], GenMapLike[A, Set[B], Map[A, Set[B]]], Iterable[(A, Set[B])], collection.Iterable[(A, Set[B])], IterableLike[(A, Set[B]), Map[A, Set[B]]], Equals, GenIterable[(A, Set[B])], GenIterableLike[(A, Set[B]), Map[A, Set[B]]], Traversable[(A, Set[B])], Mutable, collection.Traversable[(A, Set[B])], GenTraversable[(A, Set[B])], GenericTraversableTemplate[(A, Set[B]), Iterable], TraversableLike[(A, Set[B]), Map[A, Set[B]]], GenTraversableLike[(A, Set[B]), Map[A, Set[B]]], Parallelizable[(A, Set[B]), ParMap[A, Set[B]]], TraversableOnce[(A, Set[B])], GenTraversableOnce[(A, Set[B])], FilterMonadic[(A, Set[B]), Map[A, Set[B]]], HasNewBuilder[(A, Set[B]), Map[A, Set[B]]], AnyRef, Any
Ordering
1. Alphabetic
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Inherited
1. MultiMap
2. Map
3. MapLike
4. Cloneable
5. Cloneable
6. Cloneable
7. Shrinkable
8. Builder
9. Growable
10. Clearable
11. Map
12. MapLike
13. Subtractable
14. PartialFunction
15. Function1
16. GenMap
17. GenMapLike
18. Iterable
19. Iterable
20. IterableLike
21. Equals
22. GenIterable
23. GenIterableLike
24. Traversable
25. Mutable
26. Traversable
27. GenTraversable
28. GenericTraversableTemplate
29. TraversableLike
30. GenTraversableLike
31. Parallelizable
32. TraversableOnce
33. GenTraversableOnce
34. FilterMonadic
35. HasNewBuilder
36. AnyRef
37. Any
Implicitly
1. by traversable2ops
2. by MonadOps
3. by any2stringadd
4. by any2stringfmt
5. by any2ArrowAssoc
6. by any2Ensuring
7. by alternateImplicit
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Visibility
1. Public
2. All

### Type Members

1. #### class DefaultKeySet extends AbstractSet[A] with Set[A] with Serializable

The implementation class of the set returned by `keySet`.

2. #### class DefaultValuesIterable extends AbstractIterable[B] with Iterable[B] with Serializable

The implementation class of the iterable returned by `values`.

3. #### class FilteredKeys extends AbstractMap[A, B] with DefaultMap[A, B]

Attributes
protected
Definition Classes
MapLike
4. #### class MappedValues[C] extends AbstractMap[A, C] with DefaultMap[A, C]

Attributes
protected
Definition Classes
MapLike
5. #### type Self = Map[A, Set[B]]

The type implementing this traversable

The type implementing this traversable

Attributes
protected
Definition Classes
TraversableLike
6. #### class WithFilter extends FilterMonadic[A, Repr]

A class supporting filtered operations.

### Abstract Value Members

1. #### abstract def +=(kv: (A, Set[B])): MultiMap.this.type

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.

kv

the key/value pair.

returns

the map itself

Definition Classes
MapLikeBuilderGrowable
2. #### abstract def -=(key: A): MultiMap.this.type

Removes a key from this map.

Removes a key from this map.

key

the key to be removed

returns

the map itself.

Definition Classes
MapLikeShrinkable
3. #### abstract def get(key: A): Option[Set[B]]

Optionally returns the value associated with a key.

Optionally returns the value associated with a key.

key

the key value

returns

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

Definition Classes
MapLikeGenMapLike
4. #### abstract def iterator: Iterator[(A, Set[B])]

Creates a new iterator over all key/value pairs of this map

Creates a new iterator over all key/value pairs of this map

returns

the new iterator

Definition Classes
MapLikeIterableLikeGenIterableLike

### Concrete Value Members

1. #### final def !=(arg0: AnyRef): Boolean

Definition Classes
AnyRef
2. #### final def !=(arg0: Any): Boolean

Test two objects for inequality.

Test two objects for inequality.

returns

`true` if !(this == that), false otherwise.

Definition Classes
Any
3. #### final def ##(): Int

Equivalent to `x.hashCode` except for boxed numeric types and `null`.

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

returns

a hash value consistent with ==

Definition Classes
AnyRef → Any
4. #### def +[B1 >: Set[B]](elem1: (A, B1), elem2: (A, B1), elems: (A, B1)*): Map[A, B1]

Creates a new map containing two or more key/value mappings and all the key/value mappings of this map.

Creates a new map containing two or more key/value mappings and all the key/value mappings of this map.

Specified mappings will override existing mappings from this map with the same keys.

B1

the type of the added values

elem1

the first element to add.

elem2

the second element to add.

elems

the remaining elements to add.

returns

a new map containing mappings of this map and two or more specified mappings.

Definition Classes
MapLikeMapLike
Annotations
@migration
Migration

(Changed in version 2.8.0) `+` creates a new map. Use `+=` to add an element to this map and return that map itself.

5. #### def +[B1 >: Set[B]](kv: (A, B1)): Map[A, B1]

Creates a new map containing a new key/value mapping and all the key/value mappings of this map.

Creates a new map containing a new key/value mapping and all the key/value mappings of this map.

Mapping `kv` will override existing mappings from this map with the same key.

B1

the type of the value in the key/value pair.

kv

the key/value mapping to be added

returns

a new map containing mappings of this map and the mapping `kv`.

Definition Classes
MapLikeMapLikeGenMapLike
Annotations
@migration
Migration

(Changed in version 2.8.0) `+` creates a new map. Use `+=` to add an element to this map and return that map itself.

6. #### def ++[B1 >: Set[B]](xs: GenTraversableOnce[(A, B1)]): Map[A, B1]

Creates a new map containing the key/value mappings provided by the specified traversable object and all the key/value mappings of this map.

Creates a new map containing the key/value mappings provided by the specified traversable object and all the key/value mappings of this map.

Note that existing mappings from this map with the same key as those in `xs` will be overriden.

B1

the type of the added values

xs

the traversable object.

returns

a new map containing mappings of this map and those provided by `xs`.

Definition Classes
MapLikeMapLike
Annotations
@migration
Migration

(Changed in version 2.8.0) `++` creates a new map. Use `++=` to add an element to this map and return that map itself.

7. #### def ++[B](that: GenTraversableOnce[B]): MultiMap[B]

[use case] Returns a new multimap containing the elements from the left hand operand followed by the elements from the right hand operand.

[use case]

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

Example:

```scala> val a = LinkedList(1)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1)

scala> val b = LinkedList(2)
b: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

scala> val c = a ++ b
c: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)

scala> val d = LinkedList('a')
d: scala.collection.mutable.LinkedList[Char] = LinkedList(a)

scala> val e = c ++ d
e: scala.collection.mutable.LinkedList[AnyVal] = LinkedList(1, 2, a)```
B

the element type of the returned collection.

that

the traversable to append.

returns

a new multimap which contains all elements of this multimap followed by all elements of `that`.

Definition Classes
TraversableLikeGenTraversableLike
Full Signature

8. #### def ++:[B >: (A, Set[B]), That](that: collection.Traversable[B])(implicit bf: CanBuildFrom[Map[A, Set[B]], B, That]): That

As with `++`, returns a new collection containing the elements from the left operand followed by the elements from the right operand.

As with `++`, returns a new collection containing the elements from the left operand followed by the elements from the right operand.

It differs from `++` in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.

Example:

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

scala> val y = LinkedList(2)
y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

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

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

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

B

the element type of the returned collection.

That

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

that

the traversable to append.

bf

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

returns

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

Definition Classes
TraversableLike
9. #### def ++:[B](that: TraversableOnce[B]): MultiMap[B]

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

[use case]

As with `++`, returns a new collection containing the elements from the left operand followed by the elements from the right operand.

It differs from `++` in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.

Example:

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

scala> val y = LinkedList(2)
y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

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

the element type of the returned collection.

that

the traversable to append.

returns

a new multimap which contains all elements of this multimap followed by all elements of `that`.

Definition Classes
TraversableLike
Full Signature

10. #### def ++=(xs: TraversableOnce[(A, Set[B])]): MultiMap.this.type

adds all elements produced by a TraversableOnce to this multimap.

adds all elements produced by a TraversableOnce to this multimap.

xs

the TraversableOnce producing the elements to add.

returns

the multimap itself.

Definition Classes
Growable
11. #### def +=(elem1: (A, Set[B]), elem2: (A, Set[B]), elems: (A, Set[B])*): MultiMap.this.type

adds two or more elements to this multimap.

adds two or more elements to this multimap.

elem1

the first element to add.

elem2

the second element to add.

elems

the remaining elements to add.

returns

the multimap itself

Definition Classes
Growable
12. #### def -(elem1: A, elem2: A, elems: A*): Map[A, Set[B]]

Creates a new map with all the key/value mappings of this map except mappings with keys equal to any of the two or more specified keys.

Creates a new map with all the key/value mappings of this map except mappings with keys equal to any of the two or more specified keys.

elem1

the first element to remove.

elem2

the second element to remove.

elems

the remaining elements to remove.

returns

a new map containing all the mappings of this map except mappings with a key equal to `elem1`, `elem2` or any of `elems`.

Definition Classes
MapLikeSubtractable
Annotations
@migration
Migration

(Changed in version 2.8.0) `-` creates a new map. Use `-=` to remove an element from this map and return that map itself.

13. #### def -(key: A): Map[A, Set[B]]

Creates a new map with all the key/value mappings of this map except the key/value mapping with the specified key.

Creates a new map with all the key/value mappings of this map except the key/value mapping with the specified key.

key

the key to be removed

returns

a new map with all the mappings of this map except that with a key `key`.

Definition Classes
MapLikeMapLikeSubtractableGenMapLike
Annotations
@migration
Migration

(Changed in version 2.8.0) `-` creates a new map. Use `-=` to remove an element from this map and return that map itself.

14. #### def --(xs: GenTraversableOnce[A]): Map[A, Set[B]]

Creates a new map with all the key/value mappings of this map except mappings with keys equal to any of those provided by the specified traversable object.

Creates a new map with all the key/value mappings of this map except mappings with keys equal to any of those provided by the specified traversable object.

xs

the traversable object.

returns

a new map with all the key/value mappings of this map except mappings with a key equal to a key from `xs`.

Definition Classes
MapLikeSubtractable
Annotations
@migration
Migration

(Changed in version 2.8.0) `--` creates a new map. Use `--=` to remove an element from this map and return that map itself.

15. #### def --=(xs: TraversableOnce[A]): MultiMap.this.type

Removes all elements produced by an iterator from this multimap.

Removes all elements produced by an iterator from this multimap.

xs

the iterator producing the elements to remove.

returns

the multimap itself

Definition Classes
Shrinkable
16. #### def -=(elem1: A, elem2: A, elems: A*): MultiMap.this.type

Removes two or more elements from this multimap.

Removes two or more elements from this multimap.

elem1

the first element to remove.

elem2

the second element to remove.

elems

the remaining elements to remove.

returns

the multimap itself

Definition Classes
Shrinkable
17. #### def ->[B](y: B): (MultiMap[A, B], B)

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to ArrowAssoc[MultiMap[A, B]] performed by method any2ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc
Annotations
()
18. #### def /:[B](z: B)(op: (B, (A, Set[B])) ⇒ B): B

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

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

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

Examples:

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

```scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

scala> val b = (5 /: a)(_+_)
b: Int = 15

scala> val c = (5 /: a)((x,y) => x + y)
c: Int = 15```

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

B

the result type of the binary operator.

z

the start value.

op

the binary operator.

returns

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

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

where `x1, ..., xn` are the elements of this multimap.

Definition Classes
TraversableOnceGenTraversableOnce
19. #### def :\[B](z: B)(op: ((A, Set[B]), B) ⇒ B): B

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

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

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

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

Examples:

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

```scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

scala> val b = (a :\ 5)(_+_)
b: Int = 15

scala> val c = (a :\ 5)((x,y) => x + y)
c: Int = 15```
B

the result type of the binary operator.

z

the start value

op

the binary operator

returns

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

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

where `x1, ..., xn` are the elements of this multimap.

Definition Classes
TraversableOnceGenTraversableOnce
20. #### final def ==(arg0: AnyRef): Boolean

Definition Classes
AnyRef
21. #### final def ==(arg0: Any): Boolean

Test two objects for equality.

Test two objects for equality. The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

returns

`true` if the receiver object is equivalent to the argument; `false` otherwise.

Definition Classes
Any
22. #### def addBinding(key: A, value: B): MultiMap.this.type

Assigns the specified `value` to a specified `key`, replacing the existing value assigned to that `key` if it is equal to the specified value.

Assigns the specified `value` to a specified `key`, replacing the existing value assigned to that `key` if it is equal to the specified value. Otherwise, simply adds another binding to the `key`.

key

The key to which to bind the new value.

value

The value to bind to the key.

returns

A reference to this multimap.

23. #### def addString(b: scala.StringBuilder, start: String, sep: String, end: String): scala.StringBuilder

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

Appends all bindings 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 of all bindings of this map in the form of `key -> value` are separated by the string `sep`.

b

the builder to which strings are appended.

start

the starting string.

sep

the separator string.

end

the ending string.

returns

the string builder `b` to which elements were appended.

Definition Classes
MapLikeTraversableOnce
24. #### def addString(b: scala.StringBuilder): scala.StringBuilder

Appends all elements of this multimap to a string builder.

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

Example:

```scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

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

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

the string builder to which elements are appended.

returns

the string builder `b` to which elements were appended.

Definition Classes
TraversableOnce
25. #### def addString(b: scala.StringBuilder, sep: String): scala.StringBuilder

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

Appends all elements of this multimap 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 multimap, separated by the string `sep`.

Example:

```scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

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

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

the string builder to which elements are appended.

sep

the separator string.

returns

the string builder `b` to which elements were appended.

Definition Classes
TraversableOnce
26. #### def aggregate[B](z: B)(seqop: (B, (A, Set[B])) ⇒ B, combop: (B, B) ⇒ B): B

Aggregates the results of applying an operator to subsequent elements.

Aggregates the results of applying an operator to subsequent elements.

This is a more general form of `fold` and `reduce`. It has similar semantics, but does not require the result to be a supertype of the element type. It traverses the elements in different partitions sequentially, using `seqop` to update the result, and then applies `combop` to results from different partitions. The implementation of this operation may operate on an arbitrary number of collection partitions, so `combop` may be invoked an arbitrary number of times.

For example, one might want to process some elements and then produce a `Set`. In this case, `seqop` would process an element and append it to the list, while `combop` would concatenate two lists from different partitions together. The initial value `z` would be an empty set.

`pc.aggregate(Set[Int]())(_ += process(_), _ ++ _)`

Another example is calculating geometric mean from a collection of doubles (one would typically require big doubles for this).

B

the type of accumulated results

z

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

seqop

an operator used to accumulate results within a partition

combop

an associative operator used to combine results from different partitions

Definition Classes
TraversableOnceGenTraversableOnce
27. #### def andThen[C](k: (Set[B]) ⇒ C): PartialFunction[A, 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.

C

the result type of the transformation function.

k

the transformation function

returns

a partial function with the same domain as this partial function, which maps arguments `x` to `k(this(x))`.

Definition Classes
PartialFunctionFunction1
28. #### def apply(key: A): Set[B]

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`.

key

the key

returns

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

Definition Classes
MapLikeGenMapLikeFunction1
29. #### def applyOrElse[A1 <: A, B1 >: Set[B]](x: A1, default: (A1) ⇒ B1): B1

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 compiler generates `applyOrElse` implementation which avoids double evaluation of pattern matchers and guards. This makes `applyOrElse` the basis for the efficient implementation for many operations and scenarios, such as:

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

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

x

the function argument

default

the fallback function

returns

the result of this function or fallback function application.

Definition Classes
PartialFunction
Since

2.10

30. #### final def asInstanceOf[T0]: T0

Cast the receiver object to be of type `T0`.

Cast the receiver object to be of type `T0`.

Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression `1.asInstanceOf[String]` will throw a `ClassCastException` at runtime, while the expression `List(1).asInstanceOf[List[String]]` will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

returns

the receiver object.

Definition Classes
Any
Exceptions thrown
ClassCastException

if the receiver object is not an instance of the erasure of type `T0`.

31. #### def asParIterable: ParIterable[(A, Set[B])]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to TraversableOps[(A, Set[B])] performed by method traversable2ops in scala.collection.parallel.
Definition Classes
TraversableOps
32. #### def asParSeq: ParSeq[(A, Set[B])]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to TraversableOps[(A, Set[B])] performed by method traversable2ops in scala.collection.parallel.
Definition Classes
TraversableOps
33. #### def canEqual(that: Any): Boolean

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

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

that

The object with which this multimap should be compared

returns

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

Definition Classes
IterableLikeEquals
34. #### def clear(): Unit

Removes all bindings from the map.

Removes all bindings from the map. After this operation has completed, the map will be empty.

Definition Classes
MapLikeBuilderGrowableClearable
35. #### def clone(): Map[A, Set[B]]

Create a copy of the receiver object.

Create a copy of the receiver object.

The default implementation of the `clone` method is platform dependent.

returns

a copy of the receiver object.

Definition Classes
MapLikeCloneable → AnyRef
Note

not specified by SLS as a member of AnyRef

36. #### def collect[B](pf: PartialFunction[A, B]): MultiMap[B]

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

[use case]

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

B

the element type of the returned collection.

pf

the partial function which filters and maps the multimap.

returns

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

Definition Classes
TraversableLikeGenTraversableLike
Full Signature

37. #### def collectFirst[B](pf: PartialFunction[(A, Set[B]), B]): Option[B]

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

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

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

pf

the partial function

returns

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

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

38. #### def companion: GenericCompanion[Iterable]

The factory companion object that builds instances of class `MultiMap`.

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

Definition Classes
IterableIterableGenIterableTraversableTraversableGenTraversableGenericTraversableTemplate
39. #### def compose[A](g: (A) ⇒ A): (A) ⇒ Set[B]

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.

A

the type to which function `g` can be applied

g

a function A => T1

returns

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

Definition Classes
Function1
Annotations
()
40. #### def contains(key: A): Boolean

Tests whether this map contains a binding for a key.

Tests whether this map contains a binding for a key.

key

the key

returns

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

Definition Classes
MapLikeGenMapLike
41. #### def copyToArray(xs: Array[A], start: Int, len: Int): Unit

[use case] Copies elements of this multimap to an array.

[use case]

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

xs

the array to fill.

start

the starting index.

len

the maximal number of elements to copy.

Definition Classes
IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
Full Signature

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

[use case] Copies values of this multimap to an array.

[use case]

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

xs

the array to fill.

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

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

[use case] Copies values of this multimap to an array.

[use case]

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

xs

the array to fill.

start

the starting index.

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

44. #### def copyToBuffer[B >: (A, Set[B])](dest: Buffer[B]): Unit

Copies all elements of this multimap to a buffer.

Copies all elements of this multimap to a buffer.

dest

The buffer to which elements are copied.

Definition Classes
TraversableOnce
45. #### def count(p: ((A, Set[B])) ⇒ Boolean): Int

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

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

p

the predicate used to test elements.

returns

the number of elements satisfying the predicate `p`.

Definition Classes
TraversableOnceGenTraversableOnce
46. #### def default(key: A): Set[B]

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

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

key

the given key value for which a binding is missing.

Definition Classes
MapLikeGenMapLike
Exceptions thrown
`NoSuchElementException`

47. #### def drop(n: Int): Map[A, Set[B]]

Selects all elements except first n ones.

Selects all elements except first n ones.

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

n

the number of elements to drop from this multimap.

returns

a multimap consisting of all elements of this multimap except the first `n` ones, or else the empty multimap, if this multimap has less than `n` elements.

Definition Classes
IterableLikeTraversableLikeGenTraversableLike
48. #### def dropRight(n: Int): Map[A, Set[B]]

Selects all elements except last n ones.

Selects all elements except last n ones.

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

n

The number of elements to take

returns

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

Definition Classes
IterableLike
49. #### def dropWhile(p: ((A, Set[B])) ⇒ Boolean): Map[A, Set[B]]

Drops longest prefix of elements that satisfy a predicate.

Drops longest prefix of elements that satisfy a predicate.

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

returns

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

Definition Classes
TraversableLikeGenTraversableLike
50. #### def empty: Map[A, Set[B]]

The empty map of the same type as this map

The empty map of the same type as this map

returns

an empty map of type `This`.

Definition Classes
MapMapMapLike
51. #### def ensuring(cond: (MultiMap[A, B]) ⇒ Boolean, msg: ⇒ Any): MultiMap[A, B]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to Ensuring[MultiMap[A, B]] performed by method any2Ensuring in scala.Predef.
Definition Classes
Ensuring
52. #### def ensuring(cond: (MultiMap[A, B]) ⇒ Boolean): MultiMap[A, B]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to Ensuring[MultiMap[A, B]] performed by method any2Ensuring in scala.Predef.
Definition Classes
Ensuring
53. #### def ensuring(cond: Boolean, msg: ⇒ Any): MultiMap[A, B]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to Ensuring[MultiMap[A, B]] performed by method any2Ensuring in scala.Predef.
Definition Classes
Ensuring
54. #### def ensuring(cond: Boolean): MultiMap[A, B]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to Ensuring[MultiMap[A, B]] performed by method any2Ensuring in scala.Predef.
Definition Classes
Ensuring
55. #### def entryExists(key: A, p: (B) ⇒ Boolean): Boolean

Checks if there exists a binding to `key` such that it satisfies the predicate `p`.

Checks if there exists a binding to `key` such that it satisfies the predicate `p`.

key

The key for which the predicate is checked.

p

The predicate which a value assigned to the key must satisfy.

returns

A boolean if such a binding exists

56. #### final def eq(arg0: AnyRef): Boolean

Tests whether the argument (`arg0`) is a reference to the receiver object (`this`).

Tests whether the argument (`arg0`) is a reference to the receiver object (`this`).

The `eq` method implements an equivalence relation on non-null instances of `AnyRef`, and has three additional properties:

• It is consistent: for any non-null instances `x` and `y` of type `AnyRef`, multiple invocations of `x.eq(y)` consistently returns `true` or consistently returns `false`.
• For any non-null instance `x` of type `AnyRef`, `x.eq(null)` and `null.eq(x)` returns `false`.
• `null.eq(null)` returns `true`.

When overriding the `equals` or `hashCode` methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (`o1 eq o2`), they should be equal to each other (`o1 == o2`) and they should hash to the same value (`o1.hashCode == o2.hashCode`).

returns

`true` if the argument is a reference to the receiver object; `false` otherwise.

Definition Classes
AnyRef
57. #### def equals(that: Any): Boolean

Compares two maps structurally; i.

Compares two maps structurally; i.e. checks if all mappings contained in this map are also contained in the other map, and vice versa.

that

the other map

returns

`true` if both maps contain exactly the same mappings, `false` otherwise.

Definition Classes
GenMapLikeEquals → AnyRef → Any
58. #### def exists(p: ((A, Set[B])) ⇒ Boolean): Boolean

Tests whether a predicate holds for some of the elements of this multimap.

Tests whether a predicate holds for some of the elements of this multimap.

p

the predicate used to test elements.

returns

`true` if the given predicate `p` holds for some of the elements of this multimap, otherwise `false`.

Definition Classes
IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
59. #### def filter(p: ((A, Set[B])) ⇒ Boolean): Map[A, Set[B]]

Selects all elements of this multimap which satisfy a predicate.

Selects all elements of this multimap which satisfy a predicate.

p

the predicate used to test elements.

returns

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

Definition Classes
TraversableLikeGenTraversableLike
60. #### def filterKeys(p: (A) ⇒ Boolean): collection.Map[A, Set[B]]

Filters this map by retaining only keys satisfying a predicate.

Filters this map by retaining only keys satisfying a predicate.

p

the predicate used to test keys

returns

an immutable map consisting only of those key value pairs of this map where the key satisfies the predicate `p`. The resulting map wraps the original map without copying any elements.

Definition Classes
MapLikeGenMapLike
61. #### def filterNot(p: ((A, Set[B])) ⇒ Boolean): Map[A, Set[B]]

Returns a new map obtained by removing all key/value pairs for which the predicate `p` returns `true`.

Returns a new map obtained by removing all key/value pairs for which the predicate `p` returns `true`.

Note: This method works by successively removing elements for which the predicate is true from this set. If removal is slow, or you expect that most elements of the set will be removed, you might consider using `filter` with a negated predicate instead.

p

A predicate over key-value pairs

returns

A new map containing elements not satisfying the predicate.

Definition Classes
MapLikeTraversableLikeGenTraversableLike
62. #### def finalize(): Unit

Called by the garbage collector on the receiver object when there are no more references to the object.

Called by the garbage collector on the receiver object when there are no more references to the object.

The details of when and if the `finalize` method is invoked, as well as the interaction between `finalize` and non-local returns and exceptions, are all platform dependent.

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
()
Note

not specified by SLS as a member of AnyRef

63. #### def find(p: ((A, Set[B])) ⇒ Boolean): Option[(A, Set[B])]

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

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

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

p

the predicate used to test elements.

returns

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

Definition Classes
IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
64. #### def flatMap[B](f: (A) ⇒ GenTraversableOnce[B]): MultiMap[B]

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

[use case]

Builds a new collection by applying a function to all elements of this multimap 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 multimap. This might cause unexpected results sometimes. For example:

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

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

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

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

the element type of the returned collection.

f

the function to apply to each element.

returns

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

Definition Classes
TraversableLikeGenTraversableLikeFilterMonadic
Full Signature

65. #### def flatten[B]: MultiMap[B]

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

[use case]

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

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

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

val ys = Set(List(1, 2, 3), List(3, 2, 1))
// ys == Set(1, 2, 3)```
B

the type of the elements of each traversable collection.

returns

a new multimap resulting from concatenating all element multimaps.

Definition Classes
GenericTraversableTemplate
Full Signature

66. #### def fold[A1 >: (A, Set[B])](z: A1)(op: (A1, A1) ⇒ A1): A1

Folds the elements of this multimap using the specified associative binary operator.

Folds the elements of this multimap using the specified associative binary operator.

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

A1

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

z

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

op

a binary operator that must be associative

returns

the result of applying fold operator `op` between all the elements and `z`

Definition Classes
TraversableOnceGenTraversableOnce
67. #### def foldLeft[B](z: B)(op: (B, (A, Set[B])) ⇒ B): B

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

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

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

B

the result type of the binary operator.

z

the start value.

op

the binary operator.

returns

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

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

where `x1, ..., xn` are the elements of this multimap.

Definition Classes
TraversableOnceGenTraversableOnce
68. #### def foldRight[B](z: B)(op: ((A, Set[B]), B) ⇒ B): B

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

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

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

B

the result type of the binary operator.

z

the start value.

op

the binary operator.

returns

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

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

where `x1, ..., xn` are the elements of this multimap.

Definition Classes
IterableLikeTraversableOnceGenTraversableOnce
69. #### def forall(p: ((A, Set[B])) ⇒ Boolean): Boolean

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

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

p

the predicate used to test elements.

returns

`true` if the given predicate `p` holds for all elements of this multimap, otherwise `false`.

Definition Classes
IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
70. #### def foreach(f: ((A, Set[B])) ⇒ Unit): Unit

[use case] Applies a function `f` to all elements of this multimap.

[use case]

Applies a function `f` to all elements of this multimap.

Note: this method underlies the implementation of most other bulk operations. Subclasses should re-implement this method if a more efficient implementation exists.

f

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

Definition Classes
IterableLikeTraversableLikeGenTraversableLikeTraversableOnceGenTraversableOnceFilterMonadic
Full Signature

71. #### def formatted(fmtstr: String): String

Returns string formatted according to given `format` string.

Returns string formatted according to given `format` string. Format strings are as for `String.format` (@see java.lang.String.format).

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to StringFormat performed by method any2stringfmt in scala.Predef.
Definition Classes
StringFormat
Annotations
()
72. #### def genericBuilder[B]: Builder[B, Iterable[B]]

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

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

Definition Classes
GenericTraversableTemplate
73. #### final def getClass(): Class[_]

A representation that corresponds to the dynamic class of the receiver object.

A representation that corresponds to the dynamic class of the receiver object.

The nature of the representation is platform dependent.

returns

a representation that corresponds to the dynamic class of the receiver object.

Definition Classes
AnyRef → Any
Note

not specified by SLS as a member of AnyRef

74. #### def getOrElse(key: A, default: ⇒ Set[B]): Set[B]

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

[use case]

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

key

the key.

default

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

returns

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

Definition Classes
MapLikeGenMapLike
Full Signature

75. #### def getOrElseUpdate(key: A, op: ⇒ Set[B]): Set[B]

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 `op`, stores with key in map and returns that value.

key

the key to test

op

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

returns

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

Definition Classes
MapLike
76. #### def groupBy[K](f: ((A, Set[B])) ⇒ K): immutable.Map[K, Map[A, Set[B]]]

Partitions this multimap into a map of multimaps according to some discriminator function.

Partitions this multimap into a map of multimaps according to some discriminator function.

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

K

the type of keys returned by the discriminator function.

f

the discriminator function.

returns

A map from keys to multimaps such that the following invariant holds:

`(xs partition f)(k) = xs filter (x => f(x) == k)`

That is, every key `k` is bound to a multimap of those elements `x` for which `f(x)` equals `k`.

Definition Classes
TraversableLikeGenTraversableLike
77. #### def grouped(size: Int): Iterator[Map[A, Set[B]]]

Partitions elements in fixed size multimaps.

Partitions elements in fixed size multimaps.

size

the number of elements per group

returns

An iterator producing multimaps of size `size`, except the last will be truncated if the elements don't divide evenly.

Definition Classes
IterableLike
See also

scala.collection.Iterator, method `grouped`

78. #### def hasDefiniteSize: Boolean

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

Tests whether this multimap 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.

Note: many collection methods will not work on collections of infinite sizes.

returns

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

Definition Classes
TraversableLikeTraversableOnceGenTraversableOnce
79. #### def hashCode(): Int

The hashCode method for reference types.

The hashCode method for reference types. See hashCode in scala.Any.

returns

the hash code value for this object.

Definition Classes
GenMapLike → AnyRef → Any
80. #### def head: (A, Set[B])

Selects the first element of this multimap.

Selects the first element of this multimap.

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

returns

the first element of this multimap.

Definition Classes
IterableLikeTraversableLikeGenTraversableLike
Exceptions thrown
`NoSuchElementException`

if the multimap is empty.

81. #### def headOption: Option[(A, Set[B])]

Optionally selects the first element.

Optionally selects the first element.

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

returns

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

Definition Classes
TraversableLikeGenTraversableLike
82. #### def ifParSeq[R](isbody: (ParSeq[(A, Set[B])]) ⇒ R): (TraversableOps[(A, Set[B])])#Otherwise[R]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to TraversableOps[(A, Set[B])] performed by method traversable2ops in scala.collection.parallel.
Definition Classes
TraversableOps
83. #### def init: Map[A, Set[B]]

Selects all elements except the last.

Selects all elements except the last.

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

returns

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

Definition Classes
TraversableLikeGenTraversableLike
Exceptions thrown
`UnsupportedOperationException`

if the multimap is empty.

84. #### def inits: Iterator[Map[A, Set[B]]]

Iterates over the inits of this multimap.

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

returns

an iterator over all the inits of this multimap

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

85. #### def isDefinedAt(key: A): 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`.

key

the key

returns

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

Definition Classes
MapLikeGenMapLikePartialFunction
86. #### def isEmpty: Boolean

Tests whether the map is empty.

Tests whether the map is empty.

returns

`true` if the map does not contain any key/value binding, `false` otherwise.

Definition Classes
MapLikeIterableLikeTraversableLikeTraversableOnceGenTraversableOnce
87. #### final def isInstanceOf[T0]: Boolean

Test whether the dynamic type of the receiver object is `T0`.

Test whether the dynamic type of the receiver object is `T0`.

Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression `1.isInstanceOf[String]` will return `false`, while the expression `List(1).isInstanceOf[List[String]]` will return `true`. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

returns

`true` if the receiver object is an instance of erasure of type `T0`; `false` otherwise.

Definition Classes
Any
88. #### def isParIterable: Boolean

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to TraversableOps[(A, Set[B])] performed by method traversable2ops in scala.collection.parallel.
Definition Classes
TraversableOps
89. #### def isParSeq: Boolean

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to TraversableOps[(A, Set[B])] performed by method traversable2ops in scala.collection.parallel.
Definition Classes
TraversableOps
90. #### def isParallel: Boolean

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to TraversableOps[(A, Set[B])] performed by method traversable2ops in scala.collection.parallel.
Definition Classes
TraversableOps
91. #### final def isTraversableAgain: Boolean

Tests whether this multimap can be repeatedly traversed.

Tests whether this multimap can be repeatedly traversed.

returns

`true`

Definition Classes
TraversableLikeGenTraversableLikeGenTraversableOnce
92. #### def keySet: collection.Set[A]

Collects all keys of this map in a set.

Collects all keys of this map in a set.

returns

a set containing all keys of this map.

Definition Classes
MapLikeGenMapLike
93. #### def keys: collection.Iterable[A]

Collects all keys of this map in an iterable collection.

Collects all keys of this map in an iterable collection.

returns

the keys of this map as an iterable.

Definition Classes
MapLikeGenMapLike
Annotations
@migration
Migration

(Changed in version 2.8.0) `keys` returns `Iterable[A]` rather than `Iterator[A]`.

94. #### def keysIterator: Iterator[A]

Creates an iterator for all keys.

Creates an iterator for all keys.

returns

an iterator over all keys.

Definition Classes
MapLikeGenMapLike
95. #### def last: (A, Set[B])

Selects the last element.

Selects the last element.

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

returns

The last element of this multimap.

Definition Classes
TraversableLikeGenTraversableLike
Exceptions thrown
NoSuchElementException

If the multimap is empty.

96. #### def lastOption: Option[(A, Set[B])]

Optionally selects the last element.

Optionally selects the last element.

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

returns

the last element of this multimap\$ if it is nonempty, `None` if it is empty.

Definition Classes
TraversableLikeGenTraversableLike
97. #### def lift: (A) ⇒ Option[Set[B]]

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

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

returns

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

Definition Classes
PartialFunction
See also

Function.unlift

98. #### def makeSet: Set[B]

Creates a new set.

Creates a new set.

Classes that use this trait as a mixin can override this method to have the desired implementation of sets assigned to new keys. By default this is `HashSet`.

returns

An empty set of values of type `B`.

Attributes
protected
99. #### def map[B](f: (A) ⇒ B): MultiMap[B]

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

[use case]

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

B

the element type of the returned collection.

f

the function to apply to each element.

returns

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

Definition Classes
TraversableLikeGenTraversableLikeFilterMonadic
Full Signature

100. #### def mapResult[NewTo](f: (Map[A, Set[B]]) ⇒ NewTo): Builder[(A, Set[B]), NewTo]

Creates a new builder by applying a transformation function to the results of this builder.

Creates a new builder by applying a transformation function to the results of this builder.

NewTo

the type of collection returned by `f`.

f

the transformation function.

returns

a new builder which is the same as the current builder except that a transformation function is applied to this builder's result.

Definition Classes
Builder
101. #### def mapValues[C](f: (Set[B]) ⇒ C): collection.Map[A, C]

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

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

f

the function used to transform values of this map.

returns

a map view which maps every key of this map to `f(this(key))`. The resulting map wraps the original map without copying any elements.

Definition Classes
MapLikeGenMapLike
102. #### def max: A

[use case] Finds the largest element.

[use case]

Finds the largest element.

returns

the largest element of this multimap.

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

103. #### def maxBy[B](f: ((A, Set[B])) ⇒ B)(implicit cmp: Ordering[B]): (A, Set[B])

Definition Classes
TraversableOnceGenTraversableOnce
104. #### def min: A

[use case] Finds the smallest element.

[use case]

Finds the smallest element.

returns

the smallest element of this multimap

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

105. #### def minBy[B](f: ((A, Set[B])) ⇒ B)(implicit cmp: Ordering[B]): (A, Set[B])

Definition Classes
TraversableOnceGenTraversableOnce
106. #### def mkString: String

Displays all elements of this multimap in a string.

Displays all elements of this multimap in a string.

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
107. #### def mkString(sep: String): String

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

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

sep

the separator string.

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
Example:
1. `List(1, 2, 3).mkString("|") = "1|2|3"`

108. #### def mkString(start: String, sep: String, end: String): String

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

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

start

the starting string.

sep

the separator string.

end

the ending string.

returns

a string representation of this multimap. 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 multimap are separated by the string `sep`.

Definition Classes
TraversableOnceGenTraversableOnce
Example:
1. `List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"`

109. #### final def ne(arg0: AnyRef): Boolean

Equivalent to `!(this eq that)`.

Equivalent to `!(this eq that)`.

returns

`true` if the argument is not a reference to the receiver object; `false` otherwise.

Definition Classes
AnyRef
110. #### def newBuilder: Builder[(A, Set[B]), Map[A, Set[B]]]

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

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

Overrides `MapLike` implementation for better efficiency.

Attributes
protected[this]
Definition Classes
MapLikeMapLikeTraversableLikeHasNewBuilder
111. #### def nonEmpty: Boolean

Tests whether the multimap is not empty.

Tests whether the multimap is not empty.

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
112. #### final def notify(): Unit

Wakes up a single thread that is waiting on the receiver object's monitor.

Wakes up a single thread that is waiting on the receiver object's monitor.

Definition Classes
AnyRef
Note

not specified by SLS as a member of AnyRef

113. #### final def notifyAll(): Unit

Wakes up all threads that are waiting on the receiver object's monitor.

Wakes up all threads that are waiting on the receiver object's monitor.

Definition Classes
AnyRef
Note

not specified by SLS as a member of AnyRef

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

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

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

A1

the argument type of the fallback function

B1

the result type of the fallback function

that

the fallback function

returns

a partial function which has as domain the union of the domains of this partial function and `that`. The resulting partial function takes `x` to `this(x)` where `this` is defined, and to `that(x)` where it is not.

Definition Classes
PartialFunction
115. #### def par: ParMap[A, Set[B]]

Returns a parallel implementation of this collection.

Returns a parallel implementation of this collection.

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

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

All parallel collections return a reference to themselves.

returns

a parallel implementation of this collection

Definition Classes
Parallelizable
116. #### def parCombiner: Combiner[(A, Set[B]), ParMap[A, Set[B]]]

The default `par` implementation uses the combiner provided by this method to create a new parallel collection.

The default `par` implementation uses the combiner provided by this method to create a new parallel collection.

returns

a combiner for the parallel collection of type `ParRepr`

Attributes
protected[this]
Definition Classes
MapLikeMapLikeTraversableLikeParallelizable
117. #### def partition(p: ((A, Set[B])) ⇒ Boolean): (Map[A, Set[B]], Map[A, Set[B]])

Partitions this multimap in two multimaps according to a predicate.

Partitions this multimap in two multimaps according to a predicate.

p

the predicate on which to partition.

returns

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

Definition Classes
TraversableLikeGenTraversableLike
118. #### def product: A

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

[use case]

Multiplies up the elements of this collection.

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

119. #### def put(key: A, value: Set[B]): Option[Set[B]]

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.

key

the key to update

value

the new value

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.

Definition Classes
MapLike
120. #### def reduce[A1 >: (A, Set[B])](op: (A1, A1) ⇒ A1): A1

Reduces the elements of this multimap using the specified associative binary operator.

Reduces the elements of this multimap using the specified associative binary operator.

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

A1

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

op

A binary operator that must be associative.

returns

The result of applying reduce operator `op` between all the elements if the multimap is nonempty.

Definition Classes
TraversableOnceGenTraversableOnce
Exceptions thrown
UnsupportedOperationException

if this multimap is empty.

121. #### def reduceLeft[B >: (A, Set[B])](op: (B, (A, Set[B])) ⇒ B): B

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

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

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

B

the result type of the binary operator.

op

the binary operator.

returns

the result of inserting `op` between consecutive elements of this multimap, going left to right:

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

where `x1, ..., xn` are the elements of this multimap.

Definition Classes
TraversableOnce
Exceptions thrown
`UnsupportedOperationException`

if this multimap is empty.

122. #### def reduceLeftOption[B >: (A, Set[B])](op: (B, (A, Set[B])) ⇒ B): Option[B]

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

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

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

B

the result type of the binary operator.

op

the binary operator.

returns

an option value containing the result of `reduceLeft(op)` is this multimap is nonempty, `None` otherwise.

Definition Classes
TraversableOnceGenTraversableOnce
123. #### def reduceOption[A1 >: (A, Set[B])](op: (A1, A1) ⇒ A1): Option[A1]

Reduces the elements of this multimap, if any, using the specified associative binary operator.

Reduces the elements of this multimap, if any, using the specified associative binary operator.

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

A1

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

op

A binary operator that must be associative.

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
124. #### def reduceRight[B >: (A, Set[B])](op: ((A, Set[B]), B) ⇒ B): B

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

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

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

B

the result type of the binary operator.

op

the binary operator.

returns

the result of inserting `op` between consecutive elements of this multimap, going right to left:

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

where `x1, ..., xn` are the elements of this multimap.

Definition Classes
IterableLikeTraversableOnceGenTraversableOnce
Exceptions thrown
`UnsupportedOperationException`

if this multimap is empty.

125. #### def reduceRightOption[B >: (A, Set[B])](op: ((A, Set[B]), B) ⇒ B): Option[B]

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

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

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

B

the result type of the binary operator.

op

the binary operator.

returns

an option value containing the result of `reduceRight(op)` is this multimap is nonempty, `None` otherwise.

Definition Classes
TraversableOnceGenTraversableOnce
126. #### def remove(key: A): Option[Set[B]]

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.

key

the key to be removed

returns

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

Definition Classes
MapLike
127. #### def removeBinding(key: A, value: B): MultiMap.this.type

Removes the binding of `value` to `key` if it exists, otherwise this operation doesn't have any effect.

Removes the binding of `value` to `key` if it exists, otherwise this operation doesn't have any effect.

If this was the last value assigned to the specified key, the set assigned to that key will be removed as well.

key

The key of the binding.

value

The value to remove.

returns

A reference to this multimap.

128. #### def repr: Map[A, Set[B]]

The collection of type multimap underlying this `TraversableLike` object.

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

Definition Classes
TraversableLikeGenTraversableLike
129. #### def result(): Map[A, Set[B]]

The result when this map is used as a builder

The result when this map is used as a builder

returns

the map representation itself.

Definition Classes
MapLikeBuilder
130. #### def retain(p: (A, Set[B]) ⇒ Boolean): MultiMap.this.type

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

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

p

The test predicate

Definition Classes
MapLike
131. #### def reversed: List[(A, Set[B])]

Attributes
protected[this]
Definition Classes
TraversableOnce
132. #### def runWith[U](action: (Set[B]) ⇒ U): (A) ⇒ 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.

action

the action function

returns

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

Definition Classes
PartialFunction
Since

2.10

See also

`applyOrElse`.

133. #### def sameElements(that: GenIterable[A]): Boolean

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

[use case]

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

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

that

the collection to compare with.

returns

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

Definition Classes
IterableLikeGenIterableLike
Full Signature

134. #### def scan[B >: (A, Set[B]), That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Map[A, Set[B]], B, That]): That

Computes a prefix scan of the elements of the collection.

Computes a prefix scan of the elements of the collection.

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

B

element type of the resulting collection

That

type of the resulting collection

z

neutral element for the operator `op`

op

the associative operator for the scan

cbf

combiner factory which provides a combiner

returns

a new multimap containing the prefix scan of the elements in this multimap

Definition Classes
TraversableLikeGenTraversableLike
135. #### def scanLeft[B, That](z: B)(op: (B, (A, Set[B])) ⇒ B)(implicit bf: CanBuildFrom[Map[A, Set[B]], B, That]): That

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

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

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

B

the type of the elements in the resulting collection

That

the actual type of the resulting collection

z

the initial value

op

the binary operator applied to the intermediate result and the element

bf

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

returns

collection with intermediate results

Definition Classes
TraversableLikeGenTraversableLike
136. #### def scanRight[B, That](z: B)(op: ((A, Set[B]), B) ⇒ B)(implicit bf: CanBuildFrom[Map[A, Set[B]], B, That]): That

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

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

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

Example:

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

the type of the elements in the resulting collection

That

the actual type of the resulting collection

z

the initial value

op

the binary operator applied to the intermediate result and the element

bf

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

returns

collection with intermediate results

Definition Classes
TraversableLikeGenTraversableLike
Annotations
@migration
Migration

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

137. #### def seq: Map[A, Set[B]]

A version of this collection with all of the operations implemented sequentially (i.

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

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

returns

a sequential view of the collection.

Definition Classes
MapMapGenMapGenMapLikeIterableIterableGenIterableTraversableTraversableGenTraversableParallelizableTraversableOnceGenTraversableOnce
138. #### def size: Int

The size of this multimap.

The size of this multimap.

returns

the number of elements in this multimap.

Definition Classes
TraversableOnceGenTraversableOnce
139. #### def sizeHint(coll: TraversableLike[_, _], delta: Int): Unit

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

Gives a hint that one expects the `result` of this builder to have the same size as the given collection, plus some delta. This will provide a hint only if the collection is known to have a cheap `size` method. Currently this is assumed to be the case if and only if the collection is of type `IndexedSeqLike`. 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.

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.

Definition Classes
Builder
140. #### def sizeHint(coll: TraversableLike[_, _]): Unit

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

Gives a hint that one expects the `result` of this builder to have the same size as the given collection, plus some delta. This will provide a hint only if the collection is known to have a cheap `size` method. Currently this is assumed to be the case if and only if the collection is of type `IndexedSeqLike`. 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.

coll

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

Definition Classes
Builder
141. #### def sizeHint(size: Int): Unit

Gives a hint how many elements are expected to be added when the next `result` is called.

Gives a hint how many elements are expected to be added when the next `result` is called. 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.

size

the hint how many elements will be added.

Definition Classes
Builder
142. #### def sizeHintBounded(size: Int, boundingColl: TraversableLike[_, _]): 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.

size

the hint how many elements will be added.

boundingColl

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

Definition Classes
Builder
143. #### def slice(from: Int, until: Int): Map[A, Set[B]]

Selects an interval of elements.

Selects an interval of elements. The returned collection is made up of all elements `x` which satisfy the invariant:

`from <= indexOf(x) < until`

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

returns

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

Definition Classes
IterableLikeTraversableLikeGenTraversableLike
144. #### def sliding(size: Int, step: Int): Iterator[Map[A, Set[B]]]

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

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

size

the number of elements per group

step

the distance between the first elements of successive groups (defaults to 1)

returns

An iterator producing multimaps of size `size`, except the last and the only element will be truncated if there are fewer elements than size.

Definition Classes
IterableLike
See also

scala.collection.Iterator, method `sliding`

145. #### def sliding(size: Int): Iterator[Map[A, Set[B]]]

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

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

size

the number of elements per group

returns

An iterator producing multimaps of size `size`, except the last and the only element will be truncated if there are fewer elements than size.

Definition Classes
IterableLike
See also

scala.collection.Iterator, method `sliding`

146. #### def span(p: ((A, Set[B])) ⇒ Boolean): (Map[A, Set[B]], Map[A, Set[B]])

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

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

Note: `c span p` is equivalent to (but possibly more efficient than) `(c takeWhile p, c dropWhile p)`, provided the evaluation of the predicate `p` does not cause any side-effects.

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

returns

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

Definition Classes
TraversableLikeGenTraversableLike
147. #### def splitAt(n: Int): (Map[A, Set[B]], Map[A, Set[B]])

Splits this multimap into two at a given position.

Splits this multimap into two at a given position. Note: `c splitAt n` is equivalent to (but possibly more efficient than) `(c take n, c drop n)`.

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

n

the position at which to split.

returns

a pair of multimaps consisting of the first `n` elements of this multimap, and the other elements.

Definition Classes
TraversableLikeGenTraversableLike
148. #### def stringPrefix: String

Defines the prefix of this object's `toString` representation.

Defines the prefix of this object's `toString` representation.

returns

a string representation which starts the result of `toString` applied to this multimap. Unless overridden in subclasses, the string prefix of every map is `"Map"`.

Definition Classes
MapLikeTraversableLikeGenTraversableLike
149. #### def sum: A

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

[use case]

Sums up the elements of this collection.

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

150. #### final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
151. #### def tail: Map[A, Set[B]]

Selects all elements except the first.

Selects all elements except the first.

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

returns

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

Definition Classes
TraversableLikeGenTraversableLike
Exceptions thrown
`UnsupportedOperationException`

if the multimap is empty.

152. #### def tails: Iterator[Map[A, Set[B]]]

Iterates over the tails of this multimap.

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

returns

an iterator over all the tails of this multimap

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

153. #### def take(n: Int): Map[A, Set[B]]

Selects first n elements.

Selects first n elements.

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

n

the number of elements to take from this multimap.

returns

a multimap consisting only of the first `n` elements of this multimap, or else the whole multimap, if it has less than `n` elements.

Definition Classes
IterableLikeTraversableLikeGenTraversableLike
154. #### def takeRight(n: Int): Map[A, Set[B]]

Selects last n elements.

Selects last n elements.

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

n

the number of elements to take

returns

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

Definition Classes
IterableLike
155. #### def takeWhile(p: ((A, Set[B])) ⇒ Boolean): Map[A, Set[B]]

Takes longest prefix of elements that satisfy a predicate.

Takes longest prefix of elements that satisfy a predicate.

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

returns

the longest prefix of this multimap whose elements all satisfy the predicate `p`.

Definition Classes
IterableLikeTraversableLikeGenTraversableLike
156. #### def thisCollection: collection.Iterable[(A, Set[B])]

The underlying collection seen as an instance of `MultiMap`.

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

Attributes
protected[this]
Definition Classes
IterableLikeTraversableLike
157. #### def to[Col[_]]: Col[A]

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

[use case]

Converts this multimap into another by copying all elements.

Col

The collection type to build.

returns

a new collection containing all elements of this multimap.

Definition Classes
TraversableLikeTraversableOnceGenTraversableOnce
Full Signature

158. #### def toArray: Array[A]

[use case] Converts this multimap to an array.

[use case]

Converts this multimap to an array.

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

159. #### def toBuffer[C >: (A, Set[B])]: Buffer[C]

Converts this multimap to a mutable buffer.

Converts this multimap to a mutable buffer.

returns

a buffer containing all elements of this multimap.

Definition Classes
MapLikeTraversableOnceGenTraversableOnce
160. #### def toCollection(repr: Map[A, Set[B]]): collection.Iterable[(A, Set[B])]

A conversion from collections of type `Repr` to `MultiMap` objects.

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

Attributes
protected[this]
Definition Classes
IterableLikeTraversableLike
161. #### def toIndexedSeq: immutable.IndexedSeq[(A, Set[B])]

Converts this multimap to an indexed sequence.

Converts this multimap to an indexed sequence.

returns

an indexed sequence containing all elements of this multimap.

Definition Classes
TraversableOnceGenTraversableOnce
162. #### def toIterable: collection.Iterable[(A, Set[B])]

Converts this multimap to an iterable collection.

Converts this multimap to an iterable collection. Note that the choice of target `Iterable` is lazy in this default implementation as this `TraversableOnce` may be lazy and unevaluated (i.e. it may be an iterator which is only traversable once).

returns

an `Iterable` containing all elements of this multimap.

Definition Classes
IterableLikeTraversableOnceGenTraversableOnce
163. #### def toIterator: Iterator[(A, Set[B])]

Returns an Iterator over the elements in this multimap.

Returns an Iterator over the elements in this multimap. Will return the same Iterator if this instance is already an Iterator.

returns

an Iterator containing all elements of this multimap.

Definition Classes
IterableLikeTraversableLikeGenTraversableOnce
164. #### def toList: List[(A, Set[B])]

Converts this multimap to a list.

Converts this multimap to a list.

returns

a list containing all elements of this multimap.

Definition Classes
TraversableOnceGenTraversableOnce
165. #### def toMap[T, U]: collection.Map[T, U]

[use case] Converts this multimap to a map.

[use case]

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

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

166. #### def toParArray: ParArray[(A, Set[B])]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to TraversableOps[(A, Set[B])] performed by method traversable2ops in scala.collection.parallel.
Definition Classes
TraversableOps
167. #### def toSeq: collection.Seq[(A, Set[B])]

Converts this multimap to a sequence.

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

returns

a sequence containing all elements of this multimap.

Definition Classes
MapLikeTraversableOnceGenTraversableOnce
168. #### def toSet[B >: (A, Set[B])]: immutable.Set[B]

Converts this multimap to a set.

Converts this multimap to a set.

returns

a set containing all elements of this multimap.

Definition Classes
TraversableOnceGenTraversableOnce
169. #### def toStream: immutable.Stream[(A, Set[B])]

Converts this multimap to a stream.

Converts this multimap to a stream.

returns

a stream containing all elements of this multimap.

Definition Classes
IterableLikeTraversableLikeGenTraversableOnce
170. #### def toString(): String

Converts this multimap to a string.

Converts this multimap to a string.

returns

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

Definition Classes
MapLikeTraversableLikeFunction1 → AnyRef → Any
171. #### def toTraversable: collection.Traversable[(A, Set[B])]

Converts this multimap to an unspecified Traversable.

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

returns

a Traversable containing all elements of this multimap.

Definition Classes
TraversableLikeTraversableOnceGenTraversableOnce
172. #### def toVector: Vector[(A, Set[B])]

Converts this multimap to a Vector.

Converts this multimap to a Vector.

returns

a vector containing all elements of this multimap.

Definition Classes
TraversableOnceGenTraversableOnce
173. #### def transform(f: (A, Set[B]) ⇒ Set[B]): MultiMap.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.

f

the transformation to apply

returns

the map itself.

Definition Classes
MapLike
174. #### def transpose[B](implicit asTraversable: ((A, Set[B])) ⇒ GenTraversableOnce[B]): Iterable[Iterable[B]]

Transposes this multimap of traversable collections into a multimap of multimaps.

Transposes this multimap of traversable collections into a multimap of multimaps.

B

the type of the elements of each traversable collection.

asTraversable

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

returns

a two-dimensional multimap of multimaps which has as nth row the nth column of this multimap.

Definition Classes
GenericTraversableTemplate
Annotations
@migration
Migration

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

Exceptions thrown
`IllegalArgumentException`

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

175. #### def unzip[A1, A2](implicit asPair: ((A, Set[B])) ⇒ (A1, A2)): (Iterable[A1], Iterable[A2])

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

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

A1

the type of the first half of the element pairs

A2

the type of the second half of the element pairs

asPair

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

returns

a pair multimaps, containing the first, respectively second half of each element pair of this multimap.

Definition Classes
GenericTraversableTemplate
176. #### def unzip3[A1, A2, A3](implicit asTriple: ((A, Set[B])) ⇒ (A1, A2, A3)): (Iterable[A1], Iterable[A2], Iterable[A3])

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

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

A1

the type of the first member of the element triples

A2

the type of the second member of the element triples

A3

the type of the third member of the element triples

asTriple

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

returns

a triple multimaps, containing the first, second, respectively third member of each element triple of this multimap.

Definition Classes
GenericTraversableTemplate
177. #### def update(key: A, value: Set[B]): 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.

key

The key to update

value

The new value

Definition Classes
MapLike
178. #### def updated[B1 >: Set[B]](key: A, value: B1): Map[A, B1]

Creates a new map consisting of all key/value pairs of the current map plus a new pair of a given key and value.

Creates a new map consisting of all key/value pairs of the current map plus a new pair of a given key and value.

B1

the type of the added value

key

The key to add

value

The new value

returns

A fresh immutable map with the binding from `key` to `value` added to this map.

Definition Classes
MapLikeMapLike
179. #### def values: collection.Iterable[Set[B]]

Collects all values of this map in an iterable collection.

Collects all values of this map in an iterable collection.

returns

the values of this map as an iterable.

Definition Classes
MapLikeGenMapLike
Annotations
@migration
Migration

(Changed in version 2.8.0) `values` returns `Iterable[B]` rather than `Iterator[B]`.

180. #### def valuesIterator: Iterator[Set[B]]

Creates an iterator for all values in this map.

Creates an iterator for all values in this map.

returns

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

Definition Classes
MapLikeGenMapLike
181. #### def view(from: Int, until: Int): IterableView[(A, Set[B]), Map[A, Set[B]]]

Creates a non-strict view of a slice of this multimap.

Creates a non-strict view of a slice of this multimap.

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

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

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

from

the index of the first element of the view

until

the index of the element following the view

returns

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

Definition Classes
IterableLikeTraversableLike
182. #### def view: IterableView[(A, Set[B]), Map[A, Set[B]]]

Creates a non-strict view of this multimap.

Creates a non-strict view of this multimap.

returns

a non-strict view of this multimap.

Definition Classes
IterableLikeTraversableLike
183. #### final def wait(): Unit

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

Definition Classes
AnyRef
Annotations
()
185. #### final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
()
186. #### def withDefault(d: (A) ⇒ Set[B]): Map[A, Set[B]]

The same map with a given default function.

The same map with a given default function.

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

d

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

returns

a wrapper of the map with a default value

Definition Classes
Map
187. #### def withDefaultValue(d: Set[B]): Map[A, Set[B]]

The same map with a given default value.

The same map with a given default value.

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

d

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

returns

a wrapper of the map with a default value

Definition Classes
Map
188. #### def withFilter(p: ((A, Set[B])) ⇒ Boolean): FilterMonadic[(A, Set[B]), Map[A, Set[B]]]

Creates a non-strict filter of this multimap.

Creates a non-strict filter of this multimap.

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

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

p

the predicate used to test elements.

returns

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

Definition Classes
TraversableLikeFilterMonadic
189. #### def zip[B](that: GenIterable[B]): MultiMap[(A, B)]

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

[use case]

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

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

B

the type of the second half of the returned pairs

that

The iterable providing the second half of each result pair

returns

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

Definition Classes
IterableLikeGenIterableLike
Full Signature

190. #### def zipAll[B](that: collection.Iterable[B], thisElem: A, thatElem: B): MultiMap[(A, B)]

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

[use case]

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

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

B

the type of the second half of the returned pairs

that

The iterable providing the second half of each result pair

thisElem

the element to be used to fill up the result if this multimap is shorter than `that`.

thatElem

the element to be used to fill up the result if `that` is shorter than this multimap.

returns

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

Definition Classes
IterableLikeGenIterableLike
Full Signature

191. #### def zipWithIndex: MultiMap[(A, Int)]

[use case] Zips this multimap with its indices.

[use case]

Zips this multimap with its indices.

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

returns

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

Definition Classes
IterableLikeGenIterableLike
Full Signature

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

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

192. #### def →[B](y: B): (MultiMap[A, B], B)

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to ArrowAssoc[MultiMap[A, B]] performed by method any2ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc

### Shadowed Implict Value Members

1. #### def +(other: String): String

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to StringAdd performed by method any2stringadd in scala.Predef.
Shadowing
This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:
`(multiMap: StringAdd).+(other)`
Definition Classes
StringAdd
2. #### def filter(p: ((A, Set[B])) ⇒ Boolean): TraversableOnce[(A, Set[B])]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to MonadOps[(A, Set[B])] performed by method MonadOps in scala.collection.TraversableOnce.
Shadowing
This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:
`(multiMap: MonadOps[(A, Set[B])]).filter(p)`
Definition Classes
MonadOps
3. #### def flatMap[B](f: ((A, Set[B])) ⇒ GenTraversableOnce[B]): TraversableOnce[B]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to MonadOps[(A, Set[B])] performed by method MonadOps in scala.collection.TraversableOnce.
Shadowing
This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:
`(multiMap: MonadOps[(A, Set[B])]).flatMap(f)`
Definition Classes
MonadOps
4. #### def map[B](f: ((A, Set[B])) ⇒ B): TraversableOnce[B]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to MonadOps[(A, Set[B])] performed by method MonadOps in scala.collection.TraversableOnce.
Shadowing
This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:
`(multiMap: MonadOps[(A, Set[B])]).map(f)`
Definition Classes
MonadOps
5. #### val self: Any

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to StringAdd performed by method any2stringadd in scala.Predef.
Shadowing
This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
To access this member you can use a type ascription:
`(multiMap: StringAdd).self`
Definition Classes
StringAdd
6. #### val self: Any

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to StringFormat performed by method any2stringfmt in scala.Predef.
Shadowing
This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
To access this member you can use a type ascription:
`(multiMap: StringFormat).self`
Definition Classes
StringFormat
7. #### def withFilter(p: ((A, Set[B])) ⇒ Boolean): Iterator[(A, Set[B])]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to MonadOps[(A, Set[B])] performed by method MonadOps in scala.collection.TraversableOnce.
Shadowing
This implicitly inherited member is shadowed by one or more members in this class.
To access this member you can use a type ascription:
`(multiMap: MonadOps[(A, Set[B])]).withFilter(p)`
Definition Classes
MonadOps

### Deprecated Value Members

1. #### def /:\[A1 >: (A, Set[B])](z: A1)(op: (A1, A1) ⇒ A1): A1

A syntactic sugar for out of order folding.

A syntactic sugar for out of order folding. See `fold`.

Example:

```scala> val a = LinkedList(1,2,3,4)
a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4)

scala> val b = (a /:\ 5)(_+_)
b: Int = 15```
Definition Classes
GenTraversableOnce
Annotations
Deprecated

(Since version 2.10.0) use fold instead

2. #### def x: MultiMap[A, B]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to ArrowAssoc[MultiMap[A, B]] performed by method any2ArrowAssoc in scala.Predef.
Shadowing
This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
To access this member you can use a type ascription:
`(multiMap: ArrowAssoc[MultiMap[A, B]]).x`
Definition Classes
ArrowAssoc
Annotations
Deprecated

(Since version 2.10.0) Use `leftOfArrow instead`

3. #### def x: MultiMap[A, B]

Implicit information
This member is added by an implicit conversion from MultiMap[A, B] to Ensuring[MultiMap[A, B]] performed by method any2Ensuring in scala.Predef.
Shadowing
This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
To access this member you can use a type ascription:
`(multiMap: Ensuring[MultiMap[A, B]]).x`
Definition Classes
Ensuring
Annotations
Deprecated

(Since version 2.10.0) Use `resultOfEnsuring instead`