# Map

#### trait Map[A, +B] extends Iterable[(A, B)] with GenMap[A, B] with MapLike[A, B, Map[A, B]]

A map from keys of type A to values of type B.

Implementation note: This trait provides most of the operations of a Map independently of its representation. It is typically inherited by concrete implementations of maps.

To implement a concrete map, you need to provide implementations of the following methods:

def get(key: A): Option[B]
def iterator: Iterator[(A, B)]
def + [B1 >: B](kv: (A, B1)): This
def -(key: A): This

If you wish that methods like take, drop, filter also return the same kind of map you should also override:

def empty: This

It is also good idea to override methods foreach and size for efficiency.

Note: If you do not have specific implementations for add and - in mind, you might consider inheriting from DefaultMap instead.

Note: If your additions and mutations return the same kind of map as the map you are defining, you should inherit from MapLike as well.

A

the type of the keys in this map.

B

the type of the values associated with keys.

Source
Map.scala
Since

1.0

Linear Supertypes
MapLike[A, B, Map[A, B]], Subtractable[A, Map[A, B]], PartialFunction[A, B], (A) ⇒ B, GenMap[A, B], GenMapLike[A, B, Map[A, B]], Iterable[(A, B)], IterableLike[(A, B), Map[A, B]], Equals, GenIterable[(A, B)], GenIterableLike[(A, B), Map[A, B]], Traversable[(A, B)], GenTraversable[(A, B)], GenericTraversableTemplate[(A, B), Iterable], TraversableLike[(A, B), Map[A, B]], GenTraversableLike[(A, B), Map[A, B]], Parallelizable[(A, B), ParMap[A, B]], TraversableOnce[(A, B)], GenTraversableOnce[(A, B)], FilterMonadic[(A, B), Map[A, B]], HasNewBuilder[(A, B), Map[A, B]], AnyRef, Any
Known Subclasses
Ordering
1. Alphabetic
2. By inheritance
Inherited
1. Map
2. MapLike
3. Subtractable
4. PartialFunction
5. Function1
6. GenMap
7. GenMapLike
8. Iterable
9. IterableLike
10. Equals
11. GenIterable
12. GenIterableLike
13. Traversable
14. GenTraversable
15. GenericTraversableTemplate
16. TraversableLike
17. GenTraversableLike
18. Parallelizable
19. TraversableOnce
20. GenTraversableOnce
22. HasNewBuilder
23. AnyRef
24. Any
Implicitly
1. by traversable2ops
4. by any2stringfmt
5. by any2ArrowAssoc
6. by any2Ensuring
7. by alternateImplicit
1. Hide All
2. Show all
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, 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 get(key: A): Option[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
2. #### abstract def iterator: Iterator[(A, 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 +(kvs: (A, B)*): Map[A, B]

[use case] Adds key/value pairs to this map, returning a new map.

[use case]

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

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

kvs

the key/value pairs

returns

a new map with the given bindings added to this map

Definition Classes
MapLike
Full Signature

5. #### abstract def +(kv: (A, B)): Map[A, B]

[use case] Adds a key/value pair to this map, returning a new map.

[use case]

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

kv

the key/value pair

returns

a new map with the new binding added to this map

Definition Classes
MapLikeGenMapLike
Full Signature

6. #### def ++(xs: Traversable[(A, B)]): Map[A, B]

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

[use case]

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

xs

the collection containing the added key/value pairs

returns

a new map with the given bindings added to this map

Definition Classes
MapLike
Full Signature

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

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

[use case]

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

Example:

scala> val c = a ++ b

scala> val e = c ++ d
B

the element type of the returned collection.

that

the traversable to append.

returns

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

Definition Classes
TraversableLikeGenTraversableLike
Full Signature

8. #### def ++:[B >: (A, B), That](that: Traversable[B])(implicit bf: CanBuildFrom[Map[A, 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 z = x ++: y

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 map followed by all elements of that.

Definition Classes
TraversableLike
9. #### def ++:[B](that: TraversableOnce[B]): Map[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 z = x ++: y
B

the element type of the returned collection.

that

the traversable to append.

returns

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

Definition Classes
TraversableLike
Full Signature

10. #### def -(elem1: A, elem2: A, elems: A*): Map[A, B]

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

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

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

elem1

the first element to remove.

elem2

the second element to remove.

elems

the remaining elements to remove.

returns

a new map that contains all elements of the current map except one less occurrence of each of the given elements.

Definition Classes
Subtractable
11. #### abstract def -(key: A): Map[A, B]

[use case] Removes a key from this map, returning a new map.

[use case]

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

key

the key to be removed

returns

a new map without a binding for key

Definition Classes
MapLikeSubtractableGenMapLike
Full Signature

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

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

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

xs

the collection containing the removed elements.

returns

a new map that contains all elements of the current map except one less occurrence of each of the elements of elems.

Definition Classes
Subtractable
13. #### def ->[B](y: B): (Map[A, B], B)

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

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

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

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

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

Applies a binary operator to all elements of this map 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 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 map, 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 map.

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

Definition Classes
AnyRef
17. #### 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
18. #### def addString(b: StringBuilder, start: String, sep: String, end: String): 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
19. #### def addString(b: StringBuilder): StringBuilder

Appends all elements of this map to a string builder.

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

Example:

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

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
20. #### def addString(b: StringBuilder, sep: String): StringBuilder

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

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

Example:

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

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
21. #### def aggregate[B](z: B)(seqop: (B, (A, B)) ⇒ B, combop: (B, B) ⇒ B): B

Aggregates the results of applying an operator to subsequent elements.

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

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

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
23. #### def apply(key: A): 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
24. #### def applyOrElse[A1 <: A, B1 >: B](x: A1, default: (A1) ⇒ B1): B1

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

Applies 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

25. #### 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

Definition Classes
Any
Exceptions thrown
ClassCastException

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

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

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

Implicit information
This member is added by an implicit conversion from Map[A, B] to TraversableOps[(A, B)] performed by method traversable2ops in scala.collection.parallel.
Definition Classes
TraversableOps
28. #### 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 map should be compared

returns

true, if this map 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
29. #### def clone(): AnyRef

Create a copy of the receiver object.

Create a copy of the receiver object.

The default implementation of the clone method is platform dependent.

returns

a copy of the receiver object.

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

not specified by SLS as a member of AnyRef

30. #### def collect[B](pf: PartialFunction[A, B]): Map[B]

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

[use case]

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

B

the element type of the returned collection.

pf

the partial function which filters and maps the map.

returns

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

Definition Classes
TraversableLikeGenTraversableLike
Full Signature

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

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

Finds the first element of the map 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)

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

The factory companion object that builds instances of class Map.

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

Definition Classes
IterableGenIterableTraversableGenTraversableGenericTraversableTemplate
33. #### def compose[A](g: (A) ⇒ A): (A) ⇒ 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
()
34. #### 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
35. #### def copyToArray(xs: Array[A], start: Int, len: Int): Unit

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

[use case]

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

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

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

[use case]

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

xs

the array to fill.

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

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

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

[use case]

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

xs

the array to fill.

start

the starting index.

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

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

Copies all elements of this map to a buffer.

Copies all elements of this map to a buffer.

dest

The buffer to which elements are copied.

Definition Classes
TraversableOnce
39. #### def count(p: ((A, B)) ⇒ Boolean): Int

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

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

p

the predicate used to test elements.

returns

the number of elements satisfying the predicate p.

Definition Classes
TraversableOnceGenTraversableOnce
40. #### def default(key: A): B

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

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`

41. #### def drop(n: Int): Map[A, 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 map.

returns

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

Definition Classes
IterableLikeTraversableLikeGenTraversableLike
42. #### def dropRight(n: Int): Map[A, 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 map consisting of all elements of this map except the last n ones, or else the empty map, if this map has less than n elements.

Definition Classes
IterableLike
43. #### def dropWhile(p: ((A, B)) ⇒ Boolean): Map[A, 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 map whose first element does not satisfy the predicate p.

Definition Classes
TraversableLikeGenTraversableLike
44. #### def empty: Map[A, 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
MapMapLike
45. #### def ensuring(cond: (Map[A, B]) ⇒ Boolean, msg: ⇒ Any): Map[A, B]

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

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

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

Implicit information
This member is added by an implicit conversion from Map[A, B] to Ensuring[Map[A, B]] performed by method any2Ensuring in scala.Predef.
Definition Classes
Ensuring
49. #### 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
50. #### 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
51. #### def exists(p: ((A, B)) ⇒ Boolean): Boolean

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

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

p

the predicate used to test elements.

returns

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

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

Selects all elements of this map which satisfy a predicate.

Selects all elements of this map which satisfy a predicate.

p

the predicate used to test elements.

returns

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

Definition Classes
TraversableLikeGenTraversableLike
53. #### def filterKeys(p: (A) ⇒ Boolean): Map[A, 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
54. #### def filterNot(p: ((A, B)) ⇒ Boolean): Map[A, 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
55. #### 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

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

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

Finds the first element of the map 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 map that satisfies p, or None if none exists.

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

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

[use case]

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

For example:

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

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

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

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

// xs will be 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 map resulting from applying the given collection-valued function f to each element of this map and concatenating the results.

Definition Classes
Full Signature

58. #### def flatten[B]: Map[B]

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

[use case]

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

The resulting collection's type will be guided by the static type of map. 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 map resulting from concatenating all element maps.

Definition Classes
GenericTraversableTemplate
Full Signature

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

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

Folds the elements of this map 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
60. #### def foldLeft[B](z: B)(op: (B, (A, B)) ⇒ B): B

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

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

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

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

Applies a binary operator to all elements of this map 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 map, 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 map.

Definition Classes
IterableLikeTraversableOnceGenTraversableOnce
62. #### def forall(p: ((A, B)) ⇒ Boolean): Boolean

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

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

p

the predicate used to test elements.

returns

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

Definition Classes
IterableLikeTraversableLikeTraversableOnceGenTraversableOnce
63. #### def foreach(f: ((A, B)) ⇒ Unit): Unit

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

[use case]

Applies a function f to all elements of this map.

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
Full Signature

64. #### 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 Map[A, B] to StringFormat performed by method any2stringfmt in scala.Predef.
Definition Classes
StringFormat
Annotations
()
65. #### def genericBuilder[B]: Builder[B, Iterable[B]]

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

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

Definition Classes
GenericTraversableTemplate
66. #### 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

67. #### def getOrElse(key: A, default: ⇒ B): 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

68. #### def groupBy[K](f: ((A, B)) ⇒ K): immutable.Map[K, Map[A, B]]

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

Partitions this map into a map of maps 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 map.

K

the type of keys returned by the discriminator function.

f

the discriminator function.

returns

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

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

Partitions elements in fixed size maps.

Partitions elements in fixed size maps.

size

the number of elements per group

returns

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

Definition Classes
IterableLike

scala.collection.Iterator, method grouped

70. #### def hasDefiniteSize: Boolean

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

Tests whether this map 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
71. #### 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
72. #### def head: (A, B)

Selects the first element of this map.

Selects the first element of this map.

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

returns

the first element of this map.

Definition Classes
IterableLikeTraversableLikeGenTraversableLike
Exceptions thrown
`NoSuchElementException`

if the map is empty.

73. #### def headOption: Option[(A, 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 map if it is nonempty, None if it is empty.

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

Implicit information
This member is added by an implicit conversion from Map[A, B] to TraversableOps[(A, B)] performed by method traversable2ops in scala.collection.parallel.
Definition Classes
TraversableOps
75. #### def init: Map[A, 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 map consisting of all elements of this map except the last one.

Definition Classes
TraversableLikeGenTraversableLike
Exceptions thrown
`UnsupportedOperationException`

if the map is empty.

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

Iterates over the inits of this map.

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

returns

an iterator over all the inits of this map

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

77. #### 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
78. #### 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
79. #### 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
80. #### def isParIterable: Boolean

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

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

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

Tests whether this map can be repeatedly traversed.

Tests whether this map can be repeatedly traversed.

returns

true

Definition Classes
TraversableLikeGenTraversableLikeGenTraversableOnce
84. #### def keySet: 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
85. #### def keys: 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].

86. #### 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
87. #### def last: (A, 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 map.

Definition Classes
TraversableLikeGenTraversableLike
Exceptions thrown
NoSuchElementException

If the map is empty.

88. #### def lastOption: Option[(A, 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 map\$ if it is nonempty, None if it is empty.

Definition Classes
TraversableLikeGenTraversableLike
89. #### def lift: (A) ⇒ Option[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

Function.unlift

90. #### def map[B](f: (A) ⇒ B): Map[B]

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

[use case]

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

B

the element type of the returned collection.

f

the function to apply to each element.

returns

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

Definition Classes
Full Signature

91. #### def mapValues[C](f: (B) ⇒ C): 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
92. #### def max: A

[use case] Finds the largest element.

[use case]

Finds the largest element.

returns

the largest element of this map.

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

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

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

[use case] Finds the smallest element.

[use case]

Finds the smallest element.

returns

the smallest element of this map

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

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

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

Displays all elements of this map in a string.

Displays all elements of this map in a string.

returns

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

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

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

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

sep

the separator string.

returns

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

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

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

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

Displays all elements of this map 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 map. 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 map are separated by the string sep.

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

99. #### 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
100. #### def newBuilder: Builder[(A, B), Map[A, B]]

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

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

Attributes
protected[this]
Definition Classes
MapLikeTraversableLikeHasNewBuilder
101. #### def nonEmpty: Boolean

Tests whether the map is not empty.

Tests whether the map is not empty.

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
102. #### 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

103. #### 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

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

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

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
105. #### def par: ParMap[A, 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
106. #### def parCombiner: Combiner[(A, B), ParMap[A, B]]

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

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
MapLikeTraversableLikeParallelizable
107. #### def partition(p: ((A, B)) ⇒ Boolean): (Map[A, B], Map[A, B])

Partitions this map in two maps according to a predicate.

Partitions this map in two maps according to a predicate.

p

the predicate on which to partition.

returns

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

Definition Classes
TraversableLikeGenTraversableLike
108. #### 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 map 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 map and as result type of product. Examples of such types are: Long, Float, Double, BigInt.

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

109. #### def reduce[A1 >: (A, B)](op: (A1, A1) ⇒ A1): A1

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

Reduces the elements of this map 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 map is nonempty.

Definition Classes
TraversableOnceGenTraversableOnce
Exceptions thrown
UnsupportedOperationException

if this map is empty.

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

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

Applies a binary operator to all elements of this map, 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 map, going left to right:

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

where x1, ..., xn are the elements of this map.

Definition Classes
TraversableOnce
Exceptions thrown
`UnsupportedOperationException`

if this map is empty.

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

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

Optionally applies a binary operator to all elements of this map, 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 map is nonempty, None otherwise.

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

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

Reduces the elements of this map, 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
113. #### def reduceRight[B >: (A, B)](op: ((A, B), B) ⇒ B): B

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

Applies a binary operator to all elements of this map, 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 map, going right to left:

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

where x1, ..., xn are the elements of this map.

Definition Classes
IterableLikeTraversableOnceGenTraversableOnce
Exceptions thrown
`UnsupportedOperationException`

if this map is empty.

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

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

Optionally applies a binary operator to all elements of this map, 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 map is nonempty, None otherwise.

Definition Classes
TraversableOnceGenTraversableOnce
115. #### def repr: Map[A, B]

The collection of type map underlying this TraversableLike object.

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

Definition Classes
TraversableLikeGenTraversableLike
116. #### def reversed: List[(A, B)]

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

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

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

applyOrElse.

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

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

[use case]

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

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

that

the collection to compare with.

returns

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

Definition Classes
IterableLikeGenIterableLike
Full Signature

119. #### def scan[B >: (A, B), That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[Map[A, 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 map containing the prefix scan of the elements in this map

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

122. #### def seq: Map[A, 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
MapGenMapGenMapLikeIterableGenIterableTraversableGenTraversableParallelizableTraversableOnceGenTraversableOnce
123. #### def size: Int

The size of this map.

The size of this map.

returns

the number of elements in this map.

Definition Classes
TraversableOnceGenTraversableOnce
124. #### def slice(from: Int, until: Int): Map[A, 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 map containing the elements greater than or equal to index from extending up to (but not including) index until of this map.

Definition Classes
IterableLikeTraversableLikeGenTraversableLike
125. #### def sliding(size: Int, step: Int): Iterator[Map[A, 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 maps of size size, except the last and the only element will be truncated if there are fewer elements than size.

Definition Classes
IterableLike

scala.collection.Iterator, method sliding

126. #### def sliding(size: Int): Iterator[Map[A, 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 maps of size size, except the last and the only element will be truncated if there are fewer elements than size.

Definition Classes
IterableLike

scala.collection.Iterator, method sliding

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

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

Splits this map 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 map whose elements all satisfy p, and the rest of this map.

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

Splits this map into two at a given position.

Splits this map 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 maps consisting of the first n elements of this map, and the other elements.

Definition Classes
TraversableLikeGenTraversableLike
129. #### 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 map. Unless overridden in subclasses, the string prefix of every map is "Map".

Definition Classes
MapLikeTraversableLikeGenTraversableLike
130. #### 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 map 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 map and as result type of sum. Examples of such types are: Long, Float, Double, BigInt.

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

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

Definition Classes
AnyRef
132. #### def tail: Map[A, 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 map consisting of all elements of this map except the first one.

Definition Classes
TraversableLikeGenTraversableLike
Exceptions thrown
`UnsupportedOperationException`

if the map is empty.

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

Iterates over the tails of this map.

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

returns

an iterator over all the tails of this map

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

134. #### def take(n: Int): Map[A, 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 map.

returns

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

Definition Classes
IterableLikeTraversableLikeGenTraversableLike
135. #### def takeRight(n: Int): Map[A, 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 map consisting only of the last n elements of this map, or else the whole map, if it has less than n elements.

Definition Classes
IterableLike
136. #### def takeWhile(p: ((A, B)) ⇒ Boolean): Map[A, 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 map whose elements all satisfy the predicate p.

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

The underlying collection seen as an instance of Map.

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

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

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

[use case]

Converts this map into another by copying all elements.

Col

The collection type to build.

returns

a new collection containing all elements of this map.

Definition Classes
TraversableLikeTraversableOnceGenTraversableOnce
Full Signature

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

[use case] Converts this map to an array.

[use case]

Converts this map to an array.

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

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

Converts this map to a mutable buffer.

Converts this map to a mutable buffer.

returns

a buffer containing all elements of this map.

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

A conversion from collections of type Repr to Map objects.

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

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

Converts this map to an indexed sequence.

Converts this map to an indexed sequence.

returns

an indexed sequence containing all elements of this map.

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

Converts this map to an iterable collection.

Converts this map 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 map.

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

Returns an Iterator over the elements in this map.

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

returns

an Iterator containing all elements of this map.

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

Converts this map to a list.

Converts this map to a list.

returns

a list containing all elements of this map.

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

[use case] Converts this map to a map.

[use case]

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

returns

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

Definition Classes
TraversableOnceGenTraversableOnce
Full Signature

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

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

Converts this map to a sequence.

Converts this map 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 map.

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

Converts this map to a set.

Converts this map to a set.

returns

a set containing all elements of this map.

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

Converts this map to a stream.

Converts this map to a stream.

returns

a stream containing all elements of this map.

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

Converts this map to a string.

Converts this map to a string.

returns

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

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

Converts this map to an unspecified Traversable.

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

returns

a Traversable containing all elements of this map.

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

Converts this map to a Vector.

Converts this map to a Vector.

returns

a vector containing all elements of this map.

Definition Classes
TraversableOnceGenTraversableOnce
154. #### def transpose[B](implicit asTraversable: ((A, B)) ⇒ GenTraversableOnce[B]): Iterable[Iterable[B]]

Transposes this map of traversable collections into a map of maps.

Transposes this map of traversable collections into a map of maps.

B

the type of the elements of each traversable collection.

asTraversable

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

returns

a two-dimensional map of maps which has as nth row the nth column of this map.

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 map are not of the same size.

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

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

Converts this map 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 map is a pair.

returns

a pair maps, containing the first, respectively second half of each element pair of this map.

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

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

Converts this map 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 map is a triple.

returns

a triple maps, containing the first, second, respectively third member of each element triple of this map.

Definition Classes
GenericTraversableTemplate
157. #### def updated(key: A, value: B): Map[A, B]

[use case] Creates a new map obtained by updating this map with a given key/value pair.

[use case]

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

key

the key

value

the value

returns

A new map with the new key/value mapping added to this map.

Definition Classes
MapLike
Full Signature

158. #### def values: Iterable[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].

159. #### def valuesIterator: Iterator[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
160. #### def view(from: Int, until: Int): IterableView[(A, B), Map[A, B]]

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

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

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

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 map, starting at index from and extending up to (but not including) index until.

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

Creates a non-strict view of this map.

Creates a non-strict view of this map.

returns

a non-strict view of this map.

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

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

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

Definition Classes
AnyRef
Annotations
()
165. #### def withFilter(p: ((A, B)) ⇒ Boolean): FilterMonadic[(A, B), Map[A, B]]

Creates a non-strict filter of this map.

Creates a non-strict filter of this map.

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

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

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 map which satisfy the predicate p.

Definition Classes
166. #### def zip[B](that: GenIterable[B]): Map[(A, B)]

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

[use case]

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

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

B

the type of the second half of the returned pairs

that

The iterable providing the second half of each result pair

returns

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

Definition Classes
IterableLikeGenIterableLike
Full Signature

167. #### def zipAll[B](that: Iterable[B], thisElem: A, thatElem: B): Map[(A, B)]

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

[use case]

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

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

B

the type of the second half of the returned pairs

that

The iterable providing the second half of each result pair

thisElem

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

thatElem

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

returns

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

Definition Classes
IterableLikeGenIterableLike
Full Signature

168. #### def zipWithIndex: Map[(A, Int)]

[use case] Zips this map with its indices.

[use case]

Zips this map with its indices.

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

returns

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

Definition Classes
IterableLikeGenIterableLike
Full Signature

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

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

169. #### def →[B](y: B): (Map[A, B], B)

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

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

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

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

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

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

Implicit information
This member is added by an implicit conversion from Map[A, B] to StringAdd performed by method any2stringadd in scala.Predef.
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:
Definition Classes
6. #### val self: Any

Implicit information
This member is added by an implicit conversion from Map[A, B] to StringFormat performed by method any2stringfmt in scala.Predef.
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:
(map: StringFormat).self
Definition Classes
StringFormat
7. #### def withFilter(p: ((A, B)) ⇒ Boolean): Iterator[(A, B)]

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

### Deprecated Value Members

1. #### def /:\[A1 >: (A, 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 b = (a /:\ 5)(_+_)
b: Int = 15
Definition Classes
GenTraversableOnce
Annotations
Deprecated

(Since version 2.10.0) use fold instead

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

Implicit information
This member is added by an implicit conversion from Map[A, B] to ArrowAssoc[Map[A, B]] performed by method any2ArrowAssoc in scala.Predef.
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:
(map: ArrowAssoc[Map[A, B]]).x
Definition Classes
ArrowAssoc
Annotations
Deprecated

(Since version 2.10.0) Use leftOfArrow instead

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

Implicit information
This member is added by an implicit conversion from Map[A, B] to Ensuring[Map[A, B]] performed by method any2Ensuring in scala.Predef.
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:
(map: Ensuring[Map[A, B]]).x
Definition Classes
Ensuring
Annotations
Deprecated

(Since version 2.10.0) Use resultOfEnsuring instead