Scala 3/scala/scala.collection/scala.collection.concurrent/TrieMap

TrieMap

scala.collection.concurrent.TrieMap

See theTrieMap companion object

final class TrieMap[K, V] extends AbstractMap[K, V], Map[K, V], MapOps[K, V, TrieMap, TrieMap[K, V]], MapFactoryDefaults[K, V, TrieMap, Iterable], DefaultSerializable

A concurrent hash-trie or TrieMap is a concurrent thread-safe lock-free implementation of a hash array mapped trie. It is used to implement the concurrent map abstraction. It has particularly scalable concurrent insert and remove operations and is memory-efficient. It supports O(1), atomic, lock-free snapshots which are used to implement linearizable lock-free size, iterator and clear operations. The cost of evaluating the (lazy) snapshot is distributed across subsequent updates, thus making snapshot evaluation horizontally scalable.

For details, see: http://lampwww.epfl.ch/~prokopec/ctries-snapshot.pdf

Attributes

Companion: object
Source: TrieMap.scala
Graph
Supertypes: trait DefaultSerializable

trait Serializable

trait Map[K, V]

class AbstractMap[K, V]

trait Map[K, V]

trait MapOps[K, V, TrieMap, TrieMap[K, V]]

trait Shrinkable[K]

trait Builder[(K, V), TrieMap[K, V]]

trait Growable[(K, V)]

trait Clearable

trait Cloneable[TrieMap[K, V]]

trait Cloneable

trait Iterable[(K, V)]

class AbstractMap[K, V]

trait Map[K, V]

trait Equals

trait MapFactoryDefaults[K, V, TrieMap, Iterable]

trait MapOps[K, V, TrieMap, TrieMap[K, V]]

trait PartialFunction[K, V]

trait K => V

class AbstractIterable[(K, V)]

trait Iterable[(K, V)]

trait IterableFactoryDefaults[(K, V), Iterable]

trait IterableOps[(K, V), Iterable, TrieMap[K, V]]

trait IterableOnceOps[(K, V), Iterable, TrieMap[K, V]]

trait IterableOnce[(K, V)]

class Object

trait Matchable

class Any
Show all

Members list

Value members

Constructors

Attributes

Source: TrieMap.scala

Attributes

Source: TrieMap.scala

Concrete methods

Adds a single element to this concurrent map.

Value parameters

elem: the element to add.

Attributes

Returns: the concurrent map itself
Source: TrieMap.scala

Retrieves the value which is associated with the given key.

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

Value parameters

key: the key

Attributes

Returns: the value associated with the given key, or the result of the map's default method, if none exists.
Definition Classes: MapOps -> Function1
Source: TrieMap.scala

Clears the contents of this builder.

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

Attributes

Definition Classes: MapOps -> Builder -> Clearable
Source: TrieMap.scala

Attributes

Source: TrieMap.scala

Attributes

Source: TrieMap.scala

Optionally returns the value associated with a key.

Value parameters

key: the key value

Attributes

Returns: an option value containing the value associated with key in this map, or None if none exists.
Source: TrieMap.scala

If the specified key is not already in the map, computes its value using the given thunk op and enters it into the map.

If the specified mapping function throws an exception, that exception is rethrown.

Note: This method will invoke op at most once. However, op may be invoked without the result being added to the map if a concurrent process is also trying to add a value corresponding to the same key k.

Value parameters

k: the key to modify
op: the expression that computes the value

Attributes

Returns: the newly added value
Definition Classes: Map -> MapOps
Source: TrieMap.scala

Attributes

Source: TrieMap.scala

Tests whether the concurrent map is empty.

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

Attributes

Returns: true if the concurrent map contains no elements, false otherwise.
Definition Classes: IterableOnceOps
Source: TrieMap.scala

Attributes

Source: TrieMap.scala

Iterator can be used only once

Attributes

Source: TrieMap.scala

Collects all keys of this map in a set.

Attributes

Returns: a set containing all keys of this map.
Definition Classes: MapOps
Source: TrieMap.scala

Attributes

Returns: The number of elements in the collection under construction, if it can be cheaply computed, -1 otherwise. The default implementation always returns -1.
Definition Classes: MapOps -> Growable -> IterableOnce
Source: TrieMap.scala

Optionally selects the last element.

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

Attributes

Returns: the last element of this concurrent map$ if it is nonempty, None if it is empty.
Definition Classes: IterableOps
Source: TrieMap.scala

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

Attributes

Note: When implementing a custom collection type and refining CC to the new type, this method needs to be overridden to return a factory for the new type (the compiler will issue an error otherwise).
Definition Classes: Map -> Map -> MapOps
Source: TrieMap.scala

Attributes

Source: TrieMap.scala

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

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

Value parameters

key: the key to update
value: the new value

Attributes

Returns: an option value containing the value associated with the key before the put operation was executed, or None if key was not defined in the map before.
Definition Classes: MapOps
Source: TrieMap.scala

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

This is an atomic operation.

Value parameters

k: key with which the specified value is to be associated with
v: value to be associated with the specified key

Attributes

Returns: Some(oldvalue) if there was a value oldvalue previously associated with the specified key, or None if there was no mapping for the specified key
Source: TrieMap.scala

Returns a read-only snapshot of this TrieMap.

Returns a read-only snapshot of this TrieMap. This operation is lock-free and linearizable.

The snapshot is lazily updated - the first time some branch of this TrieMap are accessed, it is rewritten. The work of creating the snapshot is thus distributed across subsequent updates and accesses on this TrieMap by all threads. Note that the snapshot itself is never rewritten unlike when calling the snapshot method, but the obtained snapshot cannot be modified.

This method is used by other methods such as size and iterator.

Attributes

Source: TrieMap.scala

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

Value parameters

key: the key to be removed

Attributes

Returns: an option value containing the value associated previously with key, or None if key was not defined in the map before.
Definition Classes: MapOps
Source: TrieMap.scala

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

This is an atomic operation.

Value parameters

k: key for which the entry should be removed
v: value expected to be associated with the specified key if the removal is to take place

Attributes

Returns: true if the removal took place, false otherwise
Source: TrieMap.scala

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

This is an atomic operation.

Value parameters

k: key for which the entry should be replaced
newvalue: value to be associated with the specified key
oldvalue: value expected to be associated with the specified key if replacing is to happen

Attributes

Returns: true if the entry was replaced, false otherwise
Source: TrieMap.scala

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

This is an atomic operation.

Value parameters

k: key for which the entry should be replaced
v: value to be associated with the specified key

Attributes

Returns: Some(v) if the given key was previously mapped to some value v, or None otherwise
Source: TrieMap.scala

The size of this concurrent map.

Note: will not terminate for infinite-sized collections.

Attributes

Returns: the number of elements in this concurrent map.
Definition Classes: IterableOnceOps
Source: TrieMap.scala

Returns a snapshot of this TrieMap.

Returns a snapshot of this TrieMap. This operation is lock-free and linearizable.

The snapshot is lazily updated - the first time some branch in the snapshot or this TrieMap are accessed, they are rewritten. This means that the work of rebuilding both the snapshot and this TrieMap is distributed across all the threads doing updates or accesses subsequent to the snapshot creation.

Attributes

Source: TrieMap.scala

Attributes

Source: TrieMap.scala

Removes a single element from this concurrent map.

Value parameters

elem: the element to remove.

Attributes

Returns: the concurrent map itself
Source: TrieMap.scala

Adds a new key/value pair to this map.

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

Value parameters

key: The key to update
value: The new value

Attributes

Definition Classes: MapOps
Source: TrieMap.scala

Collects all values of this map in an iterable collection.

Attributes

Returns: the values of this map as an iterable.
Definition Classes: MapOps
Source: TrieMap.scala

A view over the elements of this collection.

Attributes

Definition Classes: MapOps -> IterableOps
Source: TrieMap.scala

Deprecated methods

Filters this map by retaining only keys satisfying a predicate.

Value parameters

p: the predicate used to test keys

Attributes

Returns: an immutable map consisting only of those key value pairs of this map where the key satisfies the predicate p. The resulting map wraps the original map without copying any elements.
Deprecated: true
Definition Classes: MapOps
Source: TrieMap.scala

Attributes

Deprecated: true
Source: TrieMap.scala

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

Value parameters

f: the function used to transform values of this map.

Attributes

Returns: a map view which maps every key of this map to f(this(key)). The resulting map wraps the original map without copying any elements.
Deprecated: true
Definition Classes: MapOps
Source: TrieMap.scala

Inherited methods

Alias for concat

Attributes

Inherited from:: IterableOps
Source: Iterable.scala

Alias for concat

Attributes

Inherited from:: MapOps
Source: Map.scala

Alias for addAll

Attributes

Inherited from:: Growable
Source: Growable.scala

Alias for addOne

Attributes

Inherited from:: Growable
Source: Growable.scala

Alias for subtractAll

Attributes

Inherited from:: Shrinkable
Source: Shrinkable.scala

Alias for subtractOne

Attributes

Inherited from:: Shrinkable
Source: Shrinkable.scala

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

Value parameters

xs: the IterableOnce producing the elements to add.

Attributes

Returns: the growable collection itself.
Inherited from:: Growable
Source: Growable.scala

Appends all elements of this collection to a string builder.

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

Example:

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

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

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

Value parameters

b: the string builder to which elements are appended.

Attributes

Returns: the string builder b to which elements were appended.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

Example:

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

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

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

Value parameters

b: the string builder to which elements are appended.
sep: the separator string.

Attributes

Returns: the string builder b to which elements were appended.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Appends all elements of this map to a string builder using start, end, and separator strings. The written text begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this map are separated by the string sep.

Example:

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

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

scala> a.addString(b , "List(" , ", " , ")")
res5: StringBuilder = List(1, 2, 3, 4)

Value parameters

b: the string builder to which elements are appended.
end: the ending string.
sep: the separator string.
start: the starting string.

Attributes

Returns: the string builder b to which elements were appended.
Definition Classes: MapOps -> IterableOnceOps
Inherited from:: MapOps
Source: Map.scala

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

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

Type parameters

C: the result type of the transformation function.

Value parameters

k: the transformation function

Attributes

Returns: a partial function with the domain of this partial function narrowed by other partial function, which maps arguments x to k(this(x)).
Inherited from:: PartialFunction
Source: PartialFunction.scala

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

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

Type parameters

C: the result type of the transformation function.

Value parameters

k: the transformation function

Attributes

Returns: a partial function with the domain of this partial function, possibly narrowed by the specified function, which maps arguments x to k(this(x)).
Definition Classes: PartialFunction -> Function1
Inherited from:: PartialFunction
Source: PartialFunction.scala

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

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

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

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

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

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

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

Value parameters

default: the fallback function
x: the function argument

Attributes

Returns: the result of this function or fallback function application.
Definition Classes: MapOps -> PartialFunction
Inherited from:: MapOps
Source: Map.scala

A method that should be called from every well-designed equals method that is open to be overridden in a subclass.

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

Value parameters

that: the value being probed for possible equality

Attributes

Returns: true if this instance can possibly equal that, otherwise false
Inherited from:: Map
Source: Map.scala

Create a copy of the receiver object.

The default implementation of the clone method is platform dependent.

Attributes

Returns: a copy of the receiver object.
Note: not specified by SLS as a member of AnyRef
Definition Classes: MapOps -> Cloneable -> Object
Inherited from:: MapOps
Source: Map.scala

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

Type parameters

B: the element type of the returned iterable collection.

Value parameters

pf: the partial function which filters and maps the iterable collection.

Attributes

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

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

Type parameters

K2: the key type of the returned map.
V2: the value type of the returned map.

Value parameters

pf: the partial function which filters and maps the map.

Attributes

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

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

Note: may not terminate for infinite-sized collections.

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

Value parameters

pf: the partial function

Attributes

Returns: an option value containing pf applied to the first value for which it is defined, or None if none exists.
Example: Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Type parameters

R: the parameter type of the transformation function.

Value parameters

k: the transformation function

Attributes

Returns: a partial function with the domain of other partial function narrowed by this partial function, which maps arguments x to this(k(x)).
Inherited from:: PartialFunction
Source: PartialFunction.scala

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

Type parameters

A: the type to which function g can be applied

Value parameters

g: a function A => T1

Attributes

Returns: a new function f such that f(x) == apply(g(x))
Inherited from:: Function1
Source: Function1.scala

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

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

Type parameters

B: the element type of the returned collection.

Value parameters

suffix: the iterable to append.

Attributes

Returns: a new iterable collection which contains all elements of this iterable collection followed by all elements of suffix.
Inherited from:: IterableOps
Source: Iterable.scala

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

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

Value parameters

suffix: the iterable to append.

Attributes

Returns: a new map which contains all elements of this map followed by all elements of suffix.
Inherited from:: MapOps
Source: Map.scala

Tests whether this map contains a binding for a key.

Value parameters

key: the key

Attributes

Returns: true if there is a binding for key in this map, false otherwise.
Inherited from:: MapOps
Source: Map.scala

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

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

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

Type parameters

B: the type of the elements of the array.

Value parameters

len: the maximal number of elements to copy.
start: the starting index of xs.
xs: the array to fill.

Attributes

Returns: the number of elements written to the array
Note: Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

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

Type parameters

B: the type of the elements of the array.

Value parameters

start: the starting index of xs.
xs: the array to fill.

Attributes

Returns: the number of elements written to the array
Note: Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

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

Type parameters

B: the type of the elements of the array.

Value parameters

xs: the array to fill.

Attributes

Returns: the number of elements written to the array
Note: Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: the type of the elements of that

Value parameters

p: the test predicate, which relates elements from both collections
that: the other collection

Attributes

Returns: true if both collections have the same length and p(x, y) is true for all corresponding elements x of this iterator and y of that, otherwise false
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

Value parameters

p: the predicate used to test elements.

Attributes

Returns: the number of elements satisfying the predicate p.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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.

Value parameters

key: the given key value for which a binding is missing.

Attributes

Inherited from:: MapOps
Source: Map.scala

Selects all elements except first n ones.

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

Value parameters

n: the number of elements to drop from this iterable collection.

Attributes

Returns: a iterable collection consisting of all elements of this iterable collection except the first n ones, or else the empty iterable collection, if this iterable collection has less than n elements. If n is negative, don't drop any elements.
Inherited from:: IterableOps
Source: Iterable.scala

Selects all elements except last n ones.

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

Value parameters

n: the number of elements to drop from this iterable collection.

Attributes

Returns: a iterable collection consisting of all elements of this iterable collection except the last n ones, or else the empty iterable collection, if this iterable collection has less than n elements. If n is negative, don't drop any elements.
Inherited from:: IterableOps
Source: Iterable.scala

Drops longest prefix of elements that satisfy a predicate.

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

Value parameters

p: The predicate used to test elements.

Attributes

Returns: the longest suffix of this iterable collection whose first element does not satisfy the predicate p.
Inherited from:: IterableOps
Source: Iterable.scala

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

Attributes

Example

val firstChar: String => Option[Char] = _.headOption
Seq("foo", "bar", "baz") match {
  case firstChar.unlift.elementWise(c0, c1, c2) =>
    println(s"$c0, $c1, $c2") // Output: f, b, b
}

Inherited from:

PartialFunction

Source

PartialFunction.scala

The empty iterable of the same type as this iterable

Attributes

Returns: an empty iterable of type C.
Definition Classes: MapFactoryDefaults -> IterableOps
Inherited from:: MapFactoryDefaults
Source: Iterable.scala

Equality of maps is implemented using the lookup method get.

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

the argument o is a Map,
the two maps have the same size, and
for every (key, value) pair in this map, other.get(key) == Some(value).

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

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

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

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

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

Value parameters

o: The map to which this map is compared

Attributes

Returns: true if the two maps are equal according to the description
Definition Classes: Map -> Equals -> Any
Inherited from:: Map
Source: Map.scala

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

Note: may not terminate for infinite-sized collections.

Value parameters

p: the predicate used to test elements.

Attributes

Returns: true if the given predicate p is satisfied by at least one element of this collection, otherwise false
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Value parameters

p: the predicate used to test elements.

Attributes

Returns: a new iterable collection consisting of all elements of this iterable collection that satisfy the given predicate p. The order of the elements is preserved.
Inherited from:: IterableOps
Source: Iterable.scala

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

Value parameters

p: The test predicate

Attributes

Inherited from:: MapOps
Source: Map.scala

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

Value parameters

pred: the predicate used to test elements.

Attributes

Returns: a new iterable collection consisting of all elements of this iterable collection that do not satisfy the given predicate pred. Their order may not be preserved.
Inherited from:: IterableOps
Source: Iterable.scala

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

Note: may not terminate for infinite-sized collections.

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

Value parameters

p: the predicate used to test elements.

Attributes

Returns: an option value containing the first element in the collection that satisfies p, or None if none exists.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

For example:

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

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

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

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

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

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

Type parameters

B: the element type of the returned collection.

Value parameters

f: the function to apply to each element.

Attributes

Returns: a new iterable collection resulting from applying the given collection-valued function f to each element of this iterable collection and concatenating the results.
Inherited from:: IterableOps
Source: Iterable.scala

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

Value parameters

f: the function to apply to each element.

Attributes

Returns: a new map resulting from applying the given collection-valued function f to each element of this map and concatenating the results.
Inherited from:: MapOps
Source: Map.scala

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

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

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

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

Type parameters

B: the type of the elements of each iterable collection.

Value parameters

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

Attributes

Returns: a new iterable collection resulting from concatenating all element iterable collections.
Inherited from:: IterableOps
Source: Iterable.scala

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

Folds the elements of this collection using the specified associative binary operator. The default implementation in IterableOnce is equivalent to foldLeft but may be overridden for more efficient traversal orders.

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

Note: will not terminate for infinite-sized collections.

Type parameters

A1: a type parameter for the binary operator, a supertype of A.

Value parameters

op: a binary operator that must be associative.
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).

Attributes

Returns: the result of applying the fold operator op between all the elements and z, or z if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.
z: the start value.

Attributes

Returns: the result of inserting op between consecutive elements of this collection, going left to right with the start value z on the left: op(...op(z, x1), x2, ..., xn) where x1, ..., xn are the elements of this collection. Returns z if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.
z: the start value.

Attributes

Returns: the result of inserting op between consecutive elements of this collection, going right to left with the start value z on the right: op(x1, op(x2, ... op(xn, z)...)) where x1, ..., xn are the elements of this collection. Returns z if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: may not terminate for infinite-sized collections.

Value parameters

p: the predicate used to test elements.

Attributes

Returns: true if this collection is empty or the given predicate p holds for all elements of this collection, otherwise false.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Attributes

Inherited from:: MapOps
Source: Map.scala

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

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

Attributes

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

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

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

Type parameters

V1: the result type of the default computation.

Value parameters

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

Attributes

Returns: the value associated with key if it exists, otherwise the result of the default computation.
Inherited from:: MapOps
Source: Map.scala

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

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

Type parameters

K: the type of keys returned by the discriminator function.

Value parameters

f: the discriminator function.

Attributes

Returns

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

(xs groupBy f)(k) = xs filter (x => f(x) == k)

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

Inherited from:

IterableOps

Source

Iterable.scala

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

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

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

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

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

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

Type parameters

B: the type of values returned by the transformation function
K: the type of keys returned by the discriminator function

Value parameters

f: the element transformation function
key: the discriminator function

Attributes

Inherited from:: IterableOps
Source: Iterable.scala

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

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

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

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

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

Attributes

Inherited from:: IterableOps
Source: Iterable.scala

Partitions elements in fixed size iterable collections.

Value parameters

size: the number of elements per group

Attributes

Returns: An iterator producing iterable collections of size size, except the last will be less than size size if the elements don't divide evenly.
See also: scala.collection.Iterator, method grouped
Inherited from:: IterableOps
Source: Iterable.scala

Calculate a hash code value for the object.

The default hashing algorithm is platform dependent.

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

Attributes

Returns: the hash code value for this object.
Definition Classes: Map -> Any
Inherited from:: Map
Source: Map.scala

Selects the first element of this iterable collection.

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

Attributes

Returns: the first element of this iterable collection.
Throws: NoSuchElementException if the iterable collection is empty.
Inherited from:: IterableOps
Source: Iterable.scala

Optionally selects the first element.

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

Attributes

Returns: the first element of this iterable collection if it is nonempty, None if it is empty.
Inherited from:: IterableOps
Source: Iterable.scala

The initial part of the collection without its last element.

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

Attributes

Inherited from:: IterableOps
Source: Iterable.scala

Iterates over the inits of this iterable collection.

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

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

Attributes

Returns: an iterator over all the inits of this iterable collection
Example: List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)
Inherited from:: IterableOps
Source: Iterable.scala

Tests whether this map contains a binding for a key.

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

Value parameters

key: the key

Attributes

Returns: true if there is a binding for key in this map, false otherwise.
Inherited from:: MapOps
Source: Map.scala

Tests whether this iterable collection can be repeatedly traversed.

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

Attributes

Returns: true if it is repeatedly traversable, false otherwise.
Definition Classes: IterableOps -> IterableOnceOps
Inherited from:: IterableOps
Source: Iterable.scala

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

Attributes

Note: When implementing a custom collection type and refining CC to the new type, this method needs to be overridden to return a factory for the new type (the compiler will issue an error otherwise).
Definition Classes: Iterable -> Iterable -> IterableOps
Inherited from:: Iterable
Source: Iterable.scala

Returns a Stepper for the keys of this map.

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

Attributes

Inherited from:: MapOps
Source: Map.scala

Collects all keys of this map in an iterable collection.

Attributes

Returns: the keys of this map as an iterable.
Inherited from:: MapOps
Source: Map.scala

Creates an iterator for all keys.

Attributes

Returns: an iterator over all keys.
Inherited from:: MapOps
Source: Map.scala

Selects the last element.

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

Attributes

Returns: The last element of this iterable collection.
Throws: NoSuchElementException If the iterable collection is empty.
Inherited from:: IterableOps
Source: Iterable.scala

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

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

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

Type parameters

B: the type of the second element in each eventual pair

Value parameters

that: the iterable providing the second element of each eventual pair

Attributes

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

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

Attributes

Returns: a function that takes an argument x to Some(this(x)) if this is defined for x, and to None otherwise.
See also: Function.unlift
Inherited from:: PartialFunction
Source: PartialFunction.scala

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

Type parameters

B: the element type of the returned iterable collection.

Value parameters

f: the function to apply to each element.

Attributes

Returns: a new iterable collection resulting from applying the given function f to each element of this iterable collection and collecting the results.
Inherited from:: IterableOps
Source: Iterable.scala

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

Value parameters

f: the function to apply to each element.

Attributes

Returns: a new map resulting from applying the given function f to each element of this map and collecting the results.
Inherited from:: MapOps
Source: Map.scala

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

Attributes

Inherited from:: Builder
Source: Builder.scala

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

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

Value parameters

f: the transformation to apply

Attributes

Returns: the map itself.
Inherited from:: MapOps
Source: Map.scala

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B: The type over which the ordering is defined.

Value parameters

ord: An ordering to be used for comparing elements.

Attributes

Returns: the largest element of this collection with respect to the ordering ord.
Throws: UnsupportedOperationException if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: The result type of the function f.

Value parameters

cmp: An ordering to be used for comparing elements.
f: The measuring function.

Attributes

Returns: the first element of this collection with the largest value measured by function f with respect to the ordering cmp.
Throws: UnsupportedOperationException if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: The result type of the function f.

Value parameters

cmp: An ordering to be used for comparing elements.
f: The measuring function.

Attributes

Returns: an option value containing the first element of this collection with the largest value measured by function f with respect to the ordering cmp.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B: The type over which the ordering is defined.

Value parameters

ord: An ordering to be used for comparing elements.

Attributes

Returns: an option value containing the largest element of this collection with respect to the ordering ord.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B: The type over which the ordering is defined.

Value parameters

ord: An ordering to be used for comparing elements.

Attributes

Returns: the smallest element of this collection with respect to the ordering ord.
Throws: UnsupportedOperationException if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: The result type of the function f.

Value parameters

cmp: An ordering to be used for comparing elements.
f: The measuring function.

Attributes

Returns: the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.
Throws: UnsupportedOperationException if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: The result type of the function f.

Value parameters

cmp: An ordering to be used for comparing elements.
f: The measuring function.

Attributes

Returns: an option value containing the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B: The type over which the ordering is defined.

Value parameters

ord: An ordering to be used for comparing elements.

Attributes

Returns: an option value containing the smallest element of this collection with respect to the ordering ord.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Displays all elements of this collection in a string.

Delegates to addString, which can be overridden.

Attributes

Returns: a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection follow each other without any separator string.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Delegates to addString, which can be overridden.

Value parameters

sep: the separator string.

Attributes

Returns: a string representation of this collection. In the resulting string the string representations (w.r.t. the method toString) of all elements of this collection are separated by the string sep.
Example: List(1, 2, 3).mkString("|") = "1|2|3"
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Delegates to addString, which can be overridden.

Value parameters

end: the ending string.
sep: the separator string.
start: the starting string.

Attributes

Returns: a string representation of this collection. The resulting string begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this collection are separated by the string sep.
Example: List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Returns: a strict builder for the same collection type. Note that in the case of lazy collections (e.g. scala.collection.View or scala.collection.immutable.LazyList), it is possible to implement this method but the resulting Builder will break laziness. As a consequence, operations should preferably be implemented with fromSpecific instead of this method.
Note: When implementing a custom collection type and refining C to the new type, this method needs to be overridden (the compiler will issue an error otherwise). In the common case where C =:= CC[A], this can be done by mixing in the scala.collection.IterableFactoryDefaults trait, which implements the method using iterableFactory.

As witnessed by the @uncheckedVariance annotation, using this method might be unsound. However, as long as the returned builder is only fed with A values taken from this instance, it is safe.
Definition Classes: MapFactoryDefaults -> IterableOps
Inherited from:: MapFactoryDefaults
Source: Iterable.scala

Tests whether the collection is not empty.

Attributes

Returns: true if the collection contains at least one element, false otherwise.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Type parameters

A1: the argument type of the fallback function
B1: the result type of the fallback function

Value parameters

that: the fallback function

Attributes

Returns: a partial function which has as domain the union of the domains of this partial function and that. The resulting partial function takes x to this(x) where this is defined, and to that(x) where it is not.
Inherited from:: PartialFunction
Source: PartialFunction.scala

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

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

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

Attributes

Inherited from:: IterableOps
Source: Iterable.scala

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

Example:

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

Type parameters

A1: the element type of the first resulting collection
A2: the element type of the second resulting collection

Value parameters

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

Attributes

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

Multiplies up the elements of this collection.

Note: will not terminate for infinite-sized collections.

Type parameters

B: the result type of the * operator.

Value parameters

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

Attributes

Returns: the product of all elements of this collection with respect to the * operator in num.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

Type parameters

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

Value parameters

op: A binary operator that must be associative.

Attributes

Returns: The result of applying reduce operator op between all the elements if the collection is nonempty.
Throws: UnsupportedOperationException if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.

Attributes

Returns: the result of inserting op between consecutive elements of this collection, going left to right: op( op( ... op(x1, x2) ..., xn-1), xn) where x1, ..., xn are the elements of this collection.
Throws: UnsupportedOperationException if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.

Attributes

Returns: an option value containing the result of reduceLeft(op) if this collection is nonempty, None otherwise.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

Type parameters

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

Value parameters

op: A binary operator that must be associative.

Attributes

Returns: An option value containing result of applying reduce operator op between all the elements if the collection is nonempty, and None otherwise.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.

Attributes

Returns: the result of inserting op between consecutive elements of this collection, going right to left: op(x1, op(x2, ..., op(xn-1, xn)...)) where x1, ..., xn are the elements of this collection.
Throws: UnsupportedOperationException if this collection is empty.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.

Attributes

Returns: an option value containing the result of reduceRight(op) if this collection is nonempty, None otherwise.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Result collection consisting of all elements appended so far.

Attributes

Inherited from:: MapOps
Source: Map.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

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

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

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

Value parameters

action: the action function

Attributes

Returns: a function which maps arguments x to isDefinedAt(x). The resulting function runs action(this(x)) where this is defined.
See also: applyOrElse.
Inherited from:: PartialFunction
Source: PartialFunction.scala

Computes a prefix scan of the elements of the collection.

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

Type parameters

B: element type of the resulting collection

Value parameters

op: the associative operator for the scan
z: neutral element for the operator op

Attributes

Returns: a new iterable collection containing the prefix scan of the elements in this iterable collection
Inherited from:: IterableOps
Source: Iterable.scala

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the type of the elements in the resulting collection

Value parameters

op: the binary operator applied to the intermediate result and the element
z: the initial value

Attributes

Returns: collection with intermediate results
Inherited from:: IterableOps
Source: Iterable.scala

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

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

Note: will not terminate for infinite-sized collections.

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

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

Example:

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

Type parameters

B: the type of the elements in the resulting collection

Value parameters

op: the binary operator applied to the intermediate result and the element
z: the initial value

Attributes

Returns: collection with intermediate results
Inherited from:: IterableOps
Source: Iterable.scala

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

Value parameters

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

Attributes

Returns

A value x where

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

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

Inherited from:

IterableOps

Source

Iterable.scala

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

Value parameters

otherSize: the test value that gets compared with the size.

Attributes

Returns

A value x where

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

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

See also

sizeIs

Inherited from:

IterableOps

Source

Iterable.scala

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

Value parameters

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.

Attributes

Inherited from:: Builder
Source: Builder.scala

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.

Value parameters

size: the hint how many elements will be added.

Attributes

Inherited from:: Builder
Source: Builder.scala

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

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

Value parameters

boundingColl: the bounding collection. If it is an IndexedSeqLike, then sizes larger than collection's size are reduced.
size: the hint how many elements will be added.

Attributes

Inherited from:: Builder
Source: Builder.scala

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

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

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

Attributes

Inherited from:: IterableOps
Source: Iterable.scala

Selects an interval of elements.

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

from <= indexOf(x) < until

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

Value parameters

from: the lowest index to include from this iterable collection.
until: the lowest index to EXCLUDE from this iterable collection.

Attributes

Returns: a iterable collection containing the elements greater than or equal to index from extending up to (but not including) index until of this iterable collection.
Inherited from:: IterableOps
Source: Iterable.scala

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

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

Value parameters

size: the number of elements per group
step: the distance between the first elements of successive groups

Attributes

Returns: An iterator producing iterable collections of size size, except the last element (which may be the only element) will be smaller if there are fewer than size elements remaining to be grouped.
See also: scala.collection.Iterator, method sliding
Example: List(1, 2, 3, 4, 5).sliding(2, 2) = Iterator(List(1, 2), List(3, 4), List(5))

List(1, 2, 3, 4, 5, 6).sliding(2, 3) = Iterator(List(1, 2), List(4, 5))
Inherited from:: IterableOps
Source: Iterable.scala

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

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

Value parameters

size: the number of elements per group

Attributes

Returns: An iterator producing iterable collections of size size, except for a non-empty collection with less than size elements, which returns an iterator that produces the source collection itself as its only element.
See also: scala.collection.Iterator, method sliding
Example: List().sliding(2) = empty iterator

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

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

List(1, 2, 3).sliding(2) = Iterator(List(1, 2), List(2, 3))
Inherited from:: IterableOps
Source: Iterable.scala

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

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

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

Value parameters

p: the test predicate

Attributes

Returns: a pair consisting of the longest prefix of this iterable collection whose elements all satisfy p, and the rest of this iterable collection.
Inherited from:: IterableOps
Source: Iterable.scala

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

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

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

Value parameters

n: the position at which to split.

Attributes

Returns: a pair of iterable collections consisting of the first n elements of this iterable collection, and the other elements.
Definition Classes: IterableOps -> IterableOnceOps
Inherited from:: IterableOps
Source: Iterable.scala

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

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

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

For collections of Int, Short, Byte or Char, an scala.collection.IntStepper is returned
For collections of Double or Float, a scala.collection.DoubleStepper is returned
For collections of Long a scala.collection.LongStepper is returned
For any other element type, an scala.collection.AnyStepper is returned

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

Attributes

Inherited from:: IterableOnce
Source: IterableOnce.scala

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

Value parameters

xs: the iterator producing the elements to remove.

Attributes

Returns: the shrinkable collection itself
Inherited from:: Shrinkable
Source: Shrinkable.scala

Sums up the elements of this collection.

Note: will not terminate for infinite-sized collections.

Type parameters

B: the result type of the + operator.

Value parameters

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

Attributes

Returns: the sum of all elements of this collection with respect to the + operator in num.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

The rest of the collection without its first element.

Attributes

Inherited from:: IterableOps
Source: Iterable.scala

Iterates over the tails of this iterable collection.

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

Attributes

Returns: an iterator over all the tails of this iterable collection
Example: List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)
Inherited from:: IterableOps
Source: Iterable.scala

Selects the first n elements.

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

Value parameters

n: the number of elements to take from this iterable collection.

Attributes

Returns: a iterable collection consisting only of the first n elements of this iterable collection, or else the whole iterable collection, if it has less than n elements. If n is negative, returns an empty iterable collection.
Inherited from:: IterableOps
Source: Iterable.scala

Selects the last n elements.

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

Value parameters

n: the number of elements to take from this iterable collection.

Attributes

Returns: a iterable collection consisting only of the last n elements of this iterable collection, or else the whole iterable collection, if it has less than n elements. If n is negative, returns an empty iterable collection.
Inherited from:: IterableOps
Source: Iterable.scala

Takes longest prefix of elements that satisfy a predicate.

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

Value parameters

p: The predicate used to test elements.

Attributes

Returns: the longest prefix of this iterable collection whose elements all satisfy the predicate p.
Inherited from:: IterableOps
Source: Iterable.scala

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

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

Type parameters

U: the return type of f

Value parameters

f: a function to apply to each element in this iterable collection

Attributes

Returns: The same logical collection as this
Definition Classes: IterableOps -> IterableOnceOps
Inherited from:: IterableOps
Source: Iterable.scala

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

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

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

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Convert collection to array.

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

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Returns: This collection as a Seq[A]. This is equivalent to to(Seq) but might be faster.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Returns a string representation of the object.

The default representation is platform dependent.

Attributes

Returns: a string representation of the object.
Definition Classes: Map -> Function1 -> Iterable -> Any
Inherited from:: Map
Source: Map.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

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

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

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

Type parameters

B: the type of the elements of each iterable collection.

Value parameters

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

Attributes

Returns: a two-dimensional iterable collection of iterable collections which has as nth row the nth column of this iterable collection.
Throws: IllegalArgumentException if all collections in this iterable collection are not of the same size.
Inherited from:: IterableOps
Source: Iterable.scala

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

Attributes

Inherited from:: PartialFunction
Source: PartialFunction.scala

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

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

Type parameters

A1: the type of the first half of the element pairs
A2: the type of the second half of the element pairs

Value parameters

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

Attributes

Returns: a pair of iterable collections, containing the first, respectively second half of each element pair of this iterable collection.
Inherited from:: IterableOps
Source: Iterable.scala

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

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

Type parameters

A1: the type of the first member of the element triples
A2: the type of the second member of the element triples
A3: the type of the third member of the element triples

Value parameters

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

Attributes

Returns: a triple of iterable collections, containing the first, second, respectively third member of each element triple of this iterable collection.
Inherited from:: IterableOps
Source: Iterable.scala

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

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

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

Value parameters

key: the key value
remappingFunction: a partial function that receives current optionally-mapped value and return a new mapping

Attributes

Returns: the new value associated with the specified key
Definition Classes: Map -> MapOps
Inherited from:: Map
Source: Map.scala

Returns a Stepper for the values of this map.

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

Attributes

Inherited from:: MapOps
Source: Map.scala

Creates an iterator for all values in this map.

Attributes

Returns: an iterator over all values that are associated with some key in this map.
Inherited from:: MapOps
Source: Map.scala

The same map with a given default function.

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

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

Value parameters

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

Attributes

Returns: a wrapper of the map with a default value
Inherited from:: Map
Source: Map.scala

The same map with a given default value.

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

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

Value parameters

d: default value used for non-present keys

Attributes

Returns: a wrapper of the map with a default value
Inherited from:: Map
Source: Map.scala

Creates a non-strict filter of this map.

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

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

Value parameters

p: the predicate used to test elements.

Attributes

Returns: an object of class WithFilter, which supports map, flatMap, foreach, and withFilter operations. All these operations apply to those elements of this map which satisfy the predicate p.
Definition Classes: MapFactoryDefaults -> IterableOps
Inherited from:: MapFactoryDefaults
Source: Iterable.scala

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

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

Type parameters

B: the type of the second half of the returned pairs

Value parameters

that: The iterable providing the second half of each result pair

Attributes

Returns: a new iterable collection containing pairs consisting of corresponding elements of this iterable collection and that. The length of the returned collection is the minimum of the lengths of this iterable collection and that.
Inherited from:: IterableOps
Source: Iterable.scala

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

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

Value parameters

that: the iterable providing the second half of each result pair
thatElem: the element to be used to fill up the result if that is shorter than this iterable collection.
thisElem: the element to be used to fill up the result if this iterable collection is shorter than that.

Attributes

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

Zips this iterable collection with its indices.

Attributes

Returns: A new iterable collection containing pairs consisting of all elements of this iterable collection paired with their index. Indices start at 0.
Example: List("a", "b", "c").zipWithIndex == List(("a", 0), ("b", 1), ("c", 2))
Inherited from:: IterableOps
Source: Iterable.scala

Deprecated and Inherited methods

Attributes

Deprecated: true
Inherited from:: MapOps
Source: Map.scala

Attributes

Deprecated: true
Inherited from:: MapOps
Source: Map.scala

Attributes

Deprecated: true
Inherited from:: IterableOps
Source: Iterable.scala

Attributes

Deprecated: true
Inherited from:: MapOps
Source: Map.scala

Adds two or more elements to this growable collection.

Value parameters

elem1: the first element to add.
elem2: the second element to add.
elems: the remaining elements to add.

Attributes

Returns: the growable collection itself
Deprecated: true
Inherited from:: Growable
Source: Growable.scala

Attributes

Deprecated: true
Inherited from:: MapOps
Source: Map.scala

Attributes

Deprecated: true
Inherited from:: MapOps
Source: Map.scala

Attributes

Deprecated: true
Inherited from:: MapOps
Source: Map.scala

Removes two or more elements from this shrinkable collection.

Value parameters

elem1: the first element to remove.
elem2: the second element to remove.
elems: the remaining elements to remove.

Attributes

Returns: the shrinkable collection itself
Deprecated: true
Inherited from:: Shrinkable
Source: Shrinkable.scala

Attributes

Deprecated: true
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Deprecated: true
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Deprecated: true
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Deprecated: true
Inherited from:: IterableOps
Source: Iterable.scala

Attributes

Deprecated: true
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

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

Attributes

Returns: true if this collection is known to have finite size, false otherwise.
See also: method knownSize for a more useful alternative
Deprecated: This method is deprecated in 2.13 because it does not provide any actionable information. As noted above, even the collection library itself does not use it. When there is no guarantee that a collection is finite, it is generally best to attempt a computation anyway and document that it will not terminate for infinite collections rather than backing out because this would prevent performing the computation on collections that are in fact finite even though hasDefiniteSize returns false.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Deprecated: true
Inherited from:: IterableOps
Source: Iterable.scala

Attributes

Deprecated: true
Inherited from:: MapOps
Source: Map.scala

Attributes

Deprecated: true
Inherited from:: Iterable
Source: Iterable.scala

Attributes

Returns: This collection as an Iterable[A]. No new collection will be built if this is already an Iterable[A].
Deprecated: true
Inherited from:: Iterable
Source: Iterable.scala

Attributes

Deprecated: true
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Deprecated: true
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Converts this iterable collection to an unspecified Iterable.

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

Attributes

Returns: An Iterable containing all elements of this iterable collection.
Deprecated: true
Inherited from:: IterableOps
Source: Iterable.scala

Attributes

Deprecated: true
Inherited from:: MapOps
Source: Map.scala

Attributes

Deprecated: true
Inherited from:: MapOps
Source: Map.scala

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

Attributes

Deprecated: true
Inherited from:: IterableOps
Source: Iterable.scala

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