Used to iterate elements using indices
Performs two tasks in parallel, and waits for both to finish.
Sequentially performs one task after another.
[use case] Returns a new parallel array containing the elements from the left hand operand followed by the elements from the right hand operand.
Returns a new parallel array containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the parallel array is the most specific superclass encompassing the element types of the two operands.
Example:
scala> val a = List(1) a: List[Int] = List(1) scala> val b = List(2) b: List[Int] = List(2) scala> val c = a ++ b c: List[Int] = List(1, 2) scala> val d = List('a') d: List[Char] = List(a) scala> val e = c ++ d e: List[AnyVal] = List(1, 2, a)
the element type of the returned collection.
the traversable to append.
a new parallel array which contains all elements of this parallel array
followed by all elements of that
.
[use case] A copy of the parallel array with an element prepended.
A copy of the parallel array with an element prepended.
Note that :-ending operators are right associative (see example).
A mnemonic for +:
vs. :+
is: the COLon goes on the COLlection side.
Also, the original parallel array is not modified, so you will want to capture the result.
Example:
scala> val x = List(1) x: List[Int] = List(1) scala> val y = 2 +: x y: List[Int] = List(2, 1) scala> println(x) List(1)
the prepended element
a new parallel array consisting of elem
followed
by all elements of this parallel array.
Applies a binary operator to a start value and all elements of this general iterable collection , going left to right.
Applies a binary operator to a start value and all elements of this general iterable collection , going left to right.
Note: /:
is alternate syntax for foldLeft
; z /: xs
is the same as
xs foldLeft z
.
Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = (5 /: a)(_+_) b: Int = 15 scala> val c = (5 /: a)((x,y) => x + y) c: Int = 15
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
the start value.
the binary operator.
the result of inserting op
between consecutive elements of this general iterable collection
,
going left to right with the start value z
on the left:
op(...op(op(z, x_1), x_2), ..., x_n)
where x_{1}, ..., x_{n}
are the elements of this general iterable collection
.
[use case] A copy of this parallel array with an element appended.
A copy of this parallel array with an element appended.
A mnemonic for +:
vs. :+
is: the COLon goes on the COLlection side.
Note: will not terminate for infinite-sized collections.
Example:
scala> val a = List(1) a: List[Int] = List(1) scala> val b = a :+ 2 b: List[Int] = List(1, 2) scala> println(a) List(1)
the appended element
a new parallel array consisting of
all elements of this parallel array followed by elem
.
Applies a binary operator to all elements of this general iterable collection and a start value, going right to left.
Applies a binary operator to all elements of this general iterable collection and a start value, going right to left.
Note: :\
is alternate syntax for foldRight
; xs :\ z
is the same as
xs foldRight z
.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.
Examples:
Note that the folding function used to compute b is equivalent to that used to compute c.
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = (a :\ 5)(_+_) b: Int = 15 scala> val c = (a :\ 5)((x,y) => x + y) c: Int = 15
the start value
the binary operator
the result of inserting op
between consecutive elements of this general iterable collection
,
going right to left with the start value z
on the right:
op(x_1, op(x_2, ... op(x_n, z)...))
where x_{1}, ..., x_{n}
are the elements of this general iterable collection
.
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 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 set, while combop
would concatenate two sets 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).
the type of accumulated results
the initial value for the accumulated result of the partition - this
will typically be the neutral element for the seqop
operator (e.g.
Nil
for list concatenation or 0
for summation) and may be evaluated
more than once
an operator used to accumulate results within a partition
an associative operator used to combine results from different partitions
Selects an element by its index in the parallel array.
Selects an element by its index in the parallel array.
Example:
scala> val x = List(1, 2, 3, 4, 5) x: List[Int] = List(1, 2, 3, 4, 5) scala> x(3) res1: Int = 4
the element of this parallel array at index idx
, where 0
indicates the first element.
if idx
does not satisfy 0 <= idx < length
.
[use case] Builds a new collection by applying a partial function to all elements of this parallel array on which the function is defined.
Builds a new collection by applying a partial function to all elements of this parallel array on which the function is defined.
the element type of the returned collection.
the partial function which filters and maps the parallel array.
a new parallel array 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.
Creates a combiner factory.
Creates a combiner factory. Each combiner factory instance is used once per invocation of a parallel transformer method for a single collection.
The default combiner factory creates a new combiner every time it
is requested, unless the combiner is thread-safe as indicated by its
canBeShared
method. In this case, the method returns a factory which
returns the same combiner each time. This is typically done for
concurrent parallel collections, the combiners of which allow
thread safe access.
The factory companion object that builds instances of class ParArray
.
The factory companion object that builds instances of class ParArray
.
(or its Iterable
superclass where class ParArray
is not a Seq
.)
[use case] Copies values of this parallel array to an array.
Copies values of this parallel array to an array.
Fills the given array xs
with values of this parallel array, beginning at index start
.
Copying will stop once either the end of the current parallel array is reached,
or the end of the array is reached.
Note: will not terminate for infinite-sized collections.
the array to fill.
the starting index.
[use case] Copies values of this parallel array to an array.
Copies values of this parallel array to an array.
Fills the given array xs
with values of this parallel array.
Copying will stop once either the end of the current parallel array is reached,
or the end of the array is reached.
Note: will not terminate for infinite-sized collections.
the array to fill.
Tests whether every element of this general sequence relates to the corresponding element of another parallel sequence by satisfying a test predicate.
Tests whether every element of this general sequence relates to the corresponding element of another parallel sequence by satisfying a test predicate.
This method will use abort
signalling capabilities. This means
that splitters may send and read abort
signals.
the type of the elements of that
the other parallel sequence
the test predicate, which relates elements from both sequences
true
if both parallel sequences have the same length and
p(x, y)
is true
for all corresponding elements x
of this general sequence
and y
of that
, otherwise false
Counts the number of elements in the general iterable collection which satisfy a predicate.
Counts the number of elements in the general iterable collection which satisfy a predicate.
the predicate used to test elements.
the number of elements satisfying the predicate p
.
[use case] Computes the multiset difference between this parallel array and another sequence.
Computes the multiset difference between this parallel array and another sequence.
Note: will not terminate for infinite-sized collections.
the sequence of elements to remove
a new parallel array which contains all elements of this parallel array
except some of occurrences of elements that also appear in that
.
If an element value x
appears
n times in that
, then the first n occurrences of x
will not form
part of the result, but any following occurrences will.
Builds a new general sequence from this general sequence without any duplicate elements.
Builds a new general sequence from this general sequence without any duplicate elements.
Note: will not terminate for infinite-sized collections.
A new general sequence which contains the first occurrence of every element of this general sequence.
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.
the number of elements to drop from this general iterable collection .
a general iterable collection
consisting of all elements of this general iterable collection
except the first n
ones, or else the
empty general iterable collection
, if this general iterable collection
has less than n
elements.
Drops all elements in the longest prefix of elements that satisfy the predicate, and returns a collection composed of the remaining elements.
Drops all elements in the longest prefix of elements that satisfy the predicate, and returns a collection composed of the remaining elements.
This method will use indexFlag
signalling capabilities. This means
that splitters may set and read the indexFlag
state.
The index flag is initially set to maximum integer value.
the predicate used to test the elements
a collection composed of all the elements after the longest prefix of elements
in this general iterable collection
that satisfy the predicate pred
Tests whether this general sequence ends with the given parallel sequence.
Tests whether this general sequence ends with the given parallel sequence.
This method will use abort
signalling capabilities. This means
that splitters may send and read abort
signals.
the type of the elements of that
sequence
the sequence to test
true
if this general sequence has that
as a suffix, false
otherwise
The equals method for arbitrary sequences.
The equals method for arbitrary sequences. Compares this sequence to some other object.
The object to compare the sequence to
true
if that
is a sequence that has the same elements as
this sequence in the same order, false
otherwise
Tests whether a predicate holds for some element of this general iterable collection .
Tests whether a predicate holds for some element of this general iterable collection .
This method will use abort
signalling capabilities. This means
that splitters may send and read abort
signals.
a predicate used to test elements
true if p
holds for some element, false otherwise
Selects all elements of this general iterable collection which satisfy a predicate.
Selects all elements of this general iterable collection which satisfy a predicate.
the predicate used to test elements.
a new general iterable collection
consisting of all elements of this general iterable collection
that satisfy the given
predicate p
. Their order may not be preserved.
Selects all elements of this general iterable collection which do not satisfy a predicate.
Selects all elements of this general iterable collection which do not satisfy a predicate.
the predicate used to test elements.
a new general iterable collection
consisting of all elements of this general iterable collection
that do not satisfy the given
predicate p
. Their order may not be preserved.
Finds some element in the collection for which the predicate holds, if such an element exists.
Finds some element in the collection for which the predicate holds, if such an element exists. The element may not necessarily be the first such element in the iteration order.
If there are multiple elements obeying the predicate, the choice is nondeterministic.
This method will use abort
signalling capabilities. This means
that splitters may send and read abort
signals.
predicate used to test the elements
an option value with the element if such an element exists, or None
otherwise
[use case] Builds a new collection by applying a function to all elements of this parallel array and using the elements of the resulting collections.
Builds a new collection by applying a function to all elements of this parallel array 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 parallel array. This might cause unexpected results sometimes. For example:
// lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet) // lettersOf will return a Set[Char], not a Seq def lettersOf(words: Seq[String]) = words.toSet flatMap (word => word.toSeq) // xs will be an Iterable[Int] val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2) // ys will be a Map[Int, Int] val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)
the element type of the returned collection.
the function to apply to each element.
a new parallel array resulting from applying the given collection-valued function
f
to each element of this parallel array and concatenating the results.
[use case] Converts this parallel array of traversable collections into a parallel array formed by the elements of these traversable collections.
Converts this parallel array of traversable collections into a parallel array formed by the elements of these traversable collections.
The resulting collection's type will be guided by the static type of parallel array. 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)
the type of the elements of each traversable collection.
a new parallel array resulting from concatenating all element parallel arrays.
Folds the elements of this sequence using the specified associative binary operator.
Folds the elements of this sequence using the specified associative binary operator. The order in which the elements are reduced is unspecified and may be nondeterministic.
Note this method has a different signature than the foldLeft
and foldRight
methods of the trait Traversable
.
The result of folding may only be a supertype of this parallel collection's
type parameter T
.
a type parameter for the binary operator, a supertype of T
.
a neutral element for the fold operation, it may be added to the result
an arbitrary number of times, not changing the result (e.g. Nil
for list concatenation,
0 for addition, or 1 for multiplication)
a binary operator that must be associative
the result of applying fold operator op
between all the elements and z
Applies a binary operator to a start value and all elements of this general iterable collection , going left to right.
Applies a binary operator to a start value and all elements of this general iterable 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.
the start value.
the binary operator.
the result of inserting op
between consecutive elements of this general iterable collection
,
going left to right with the start value z
on the left:
op(...op(z, x_1), x_2, ..., x_n)
where x_{1}, ..., x_{n}
are the elements of this general iterable collection
.
Applies a binary operator to all elements of this general iterable collection and a start value, going right to left.
Applies a binary operator to all elements of this general iterable 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.
the start value.
the binary operator.
the result of inserting op
between consecutive elements of this general iterable collection
,
going right to left with the start value z
on the right:
op(x_1, op(x_2, ... op(x_n, z)...))
where x_{1}, ..., x_{n}
are the elements of this general iterable collection
.
Tests whether a predicate holds for all elements of this general iterable collection .
Tests whether a predicate holds for all elements of this general iterable collection .
This method will use abort
signalling capabilities. This means
that splitters may send and read abort
signals.
a predicate used to test elements
true if p
holds for all elements, false otherwise
Applies a function f
to all the elements of general iterable collection
in an undefined order.
Applies a function f
to all the elements of general iterable collection
in an undefined order.
the result type of the function applied to each element, which is always discarded
function applied to each element
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).
The generic builder that builds instances of CC at arbitrary element types.
The generic builder that builds instances of CC at arbitrary element types.
Partitions this general iterable collection into a map of general iterable collection s according to some discriminator function.
Partitions this general iterable collection into a map of general iterable collection s 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 general iterable collection .
the type of keys returned by the discriminator function.
the discriminator function.
A map from keys to general iterable collection s 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 general iterable collection
of those elements x
for which f(x)
equals k
.
Hashcodes for GenSeq produce a value from the hashcodes of all the elements of the general sequence.
Hashcodes for GenSeq produce a value from the hashcodes of all the elements of the general sequence.
Selects the first element of this general iterable collection .
Selects the first element of this general iterable collection .
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this general iterable collection .
if the general iterable collection is empty.
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.
the first element of this general iterable collection
if it is nonempty,
None
if it is empty.
[use case] Finds index of first occurrence of some value in this parallel array after or at some start index.
Finds index of first occurrence of some value in this parallel array after or at some start index.
Note: may not terminate for infinite-sized collections.
the element value to search for.
the start index
the index >= from
of the first element of this parallel array that is equal (as determined by ==
)
to elem
, or -1
, if none exists.
[use case] Finds index of first occurrence of some value in this parallel array.
Finds index of first occurrence of some value in this parallel array.
Note: may not terminate for infinite-sized collections.
the element value to search for.
the index of the first element of this parallel array that is equal (as determined by ==
)
to elem
, or -1
, if none exists.
Finds the first element satisfying some predicate.
Finds the first element satisfying some predicate.
This method will use indexFlag
signalling capabilities. This means
that splitters may set and read the indexFlag
state.
The index flag is initially set to maximum integer value.
the predicate used to test the elements
the starting offset for the search
the index >= from
of the first element of this general sequence that satisfies the predicate p
,
or -1
, if none exists
Finds index of first element satisfying some predicate.
Finds index of first element satisfying some predicate.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
the index of the first element of this general sequence that satisfies the predicate p
,
or -1
, if none exists.
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.
a general iterable collection consisting of all elements of this general iterable collection
except the last one.
if the general iterable collection is empty.
[use case] Computes the multiset intersection between this parallel array and another sequence.
Computes the multiset intersection between this parallel array and another sequence.
Note: may not terminate for infinite-sized collections.
the sequence of elements to intersect with.
a new parallel array which contains all elements of this parallel array
which also appear in that
.
If an element value x
appears
n times in that
, then the first n occurrences of x
will be retained
in the result, but any following occurrences will be omitted.
Tests whether this general sequence contains given index.
Tests whether this general sequence contains given index.
The implementations of methods apply
and isDefinedAt
turn a Seq[A]
into
a PartialFunction[Int, A]
.
the index to test
true
if this general sequence contains an element at position idx
, false
otherwise.
Tests whether the general iterable collection is empty.
Tests whether the general iterable collection is empty.
true
if the general iterable collection
contains no elements, false
otherwise.
Denotes whether this parallel collection has strict splitters.
Denotes whether this parallel collection has strict splitters.
This is true in general, and specific collection instances may choose to
override this method. Such collections will fail to execute methods
which rely on splitters being strict, i.e. returning a correct value
in the remaining
method.
This method helps ensure that such failures occur on method invocations, rather than later on and in unpredictable ways.
Tests whether this general iterable collection can be repeatedly traversed.
Tests whether this general iterable collection can be repeatedly traversed.
true
Creates a new split iterator used to traverse the elements of this collection.
Creates a new split iterator used to traverse the elements of this collection.
By default, this method is implemented in terms of the protected splitter
method.
a split iterator
Selects the last element.
Selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
The last element of this general iterable collection .
If the general iterable collection is empty.
[use case] Finds index of last occurrence of some value in this parallel array before or at a given end index.
Finds index of last occurrence of some value in this parallel array before or at a given end index.
the element value to search for.
the end index.
the index <= end
of the last element of this parallel array that is equal (as determined by ==
)
to elem
, or -1
, if none exists.
[use case] Finds index of last occurrence of some value in this parallel array.
Finds index of last occurrence of some value in this parallel array.
Note: will not terminate for infinite-sized collections.
the element value to search for.
the index of the last element of this parallel array that is equal (as determined by ==
)
to elem
, or -1
, if none exists.
Finds the last element satisfying some predicate.
Finds the last element satisfying some predicate.
This method will use indexFlag
signalling capabilities. This means
that splitters may set and read the indexFlag
state.
The index flag is initially set to minimum integer value.
the predicate used to test the elements
the maximum offset for the search
the index <= end
of the first element of this general sequence that satisfies the predicate p
,
or -1
, if none exists
Finds index of last element satisfying some predicate.
Finds index of last element satisfying some predicate.
Note: will not terminate for infinite-sized collections.
the predicate used to test elements.
the index of the last element of this general sequence that satisfies the predicate p
,
or -1
, if none exists.
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.
the last element of this general iterable collection
$ if it is nonempty,
None
if it is empty.
The length of the parallel array.
The length of the parallel array.
Note: will not terminate for infinite-sized collections.
Note: xs.length
and xs.size
yield the same result.
the number of elements in this parallel array.
[use case] Builds a new collection by applying a function to all elements of this parallel array.
Builds a new collection by applying a function to all elements of this parallel array.
the element type of the returned collection.
the function to apply to each element.
a new parallel array resulting from applying the given function
f
to each element of this parallel array and collecting the results.
[use case] Finds the largest element.
Finds the largest element.
the largest element of this parallel array.
[use case] Finds the first element which yields the largest value measured by function f.
Finds the first element which yields the largest value measured by function f.
The result type of the function f.
The measuring function.
the first element of this parallel array with the largest value measured by function f.
[use case] Finds the smallest element.
Finds the smallest element.
the smallest element of this parallel array
[use case] Finds the first element which yields the smallest value measured by function f.
Finds the first element which yields the smallest value measured by function f.
The result type of the function f.
The measuring function.
the first element of this parallel array with the smallest value measured by function f.
Displays all elements of this general iterable collection in a string.
Displays all elements of this general iterable collection in a string.
a string representation of this general iterable collection
. In the resulting string
the string representations (w.r.t. the method toString
)
of all elements of this general iterable collection
follow each other without any
separator string.
Displays all elements of this general iterable collection in a string using a separator string.
Displays all elements of this general iterable collection in a string using a separator string.
the separator string.
a string representation of this general iterable collection
. In the resulting string
the string representations (w.r.t. the method toString
)
of all elements of this general iterable collection
are separated by the string sep
.
List(1, 2, 3).mkString("|") = "1|2|3"
Displays all elements of this general iterable collection in a string using start, end, and separator strings.
Displays all elements of this general iterable collection in a string using start, end, and separator strings.
the starting string.
the separator string.
the ending string.
a string representation of this general iterable 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 general iterable collection
are separated by
the string sep
.
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
The builder that builds instances of type CC[A]
The builder that builds instances of type CC[A]
Tests whether the general iterable collection is not empty.
Tests whether the general iterable collection is not empty.
true
if the general iterable collection
contains at least one element, false
otherwise.
[use case] A copy of this parallel array with an element value appended until a given target length is reached.
A copy of this parallel array with an element value appended until a given target length is reached.
the target length
the padding value
a new parallel array consisting of
all elements of this parallel array followed by the minimal number of occurrences of elem
so
that the resulting parallel array has a length of at least len
.
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.
a parallel implementation of this collection
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.
a combiner for the parallel collection of type ParRepr
Partitions this general iterable collection in two general iterable collection s according to a predicate.
Partitions this general iterable collection in two general iterable collection s according to a predicate.
the predicate on which to partition.
a pair of general iterable collection
s: the first general iterable collection
consists of all elements that
satisfy the predicate p
and the second general iterable collection
consists of all elements
that don't. The relative order of the elements in the resulting general iterable collection
s
may not be preserved.
[use case] Produces a new parallel array where a slice of elements in this parallel array is replaced by another sequence.
Produces a new parallel array where a slice of elements in this parallel array is replaced by another sequence.
the index of the first replaced element
the number of elements to drop in the original parallel array
a new parallel array consisting of all elements of this parallel array
except that replaced
elements starting from from
are replaced
by patch
.
Returns the length of the longest prefix whose elements all satisfy some predicate.
Returns the length of the longest prefix whose elements all satisfy some predicate.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
the length of the longest prefix of this general sequence
such that every element of the segment satisfies the predicate p
.
[use case] Multiplies up the elements of this collection.
Multiplies up the elements of this collection.
the product of all elements in this parallel array 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 parallel array and as result type of product
.
Examples of such types are: Long
, Float
, Double
, BigInt
.
Reduces the elements of this sequence using the specified associative binary operator.
Reduces the elements of this sequence using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Note this method has a different signature than the reduceLeft
and reduceRight
methods of the trait Traversable
.
The result of reducing may only be a supertype of this parallel collection's
type parameter T
.
A type parameter for the binary operator, a supertype of T
.
A binary operator that must be associative.
The result of applying reduce operator op
between all the elements if the collection is nonempty.
if this general iterable collection is empty.
Optionally applies a binary operator to all elements of this general iterable collection , going left to right.
Optionally applies a binary operator to all elements of this general iterable 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.
the binary operator.
an option value containing the result of reduceLeft(op)
is this general iterable collection
is nonempty,
None
otherwise.
Optionally reduces the elements of this sequence using the specified associative binary operator.
Optionally reduces the elements of this sequence using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Note this method has a different signature than the reduceLeftOption
and reduceRightOption
methods of the trait Traversable
.
The result of reducing may only be a supertype of this parallel collection's
type parameter T
.
A type parameter for the binary operator, a supertype of T
.
A binary operator that must be associative.
An option value containing result of applying reduce operator op
between all
the elements if the collection is nonempty, and None
otherwise.
Applies a binary operator to all elements of this general iterable collection , going right to left.
Applies a binary operator to all elements of this general iterable 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.
the binary operator.
the result of inserting op
between consecutive elements of this general iterable collection
,
going right to left:
op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
where x_{1}, ..., x_{n}
are the elements of this general iterable collection
.
if this general iterable collection is empty.
Optionally applies a binary operator to all elements of this general iterable collection , going right to left.
Optionally applies a binary operator to all elements of this general iterable 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.
the binary operator.
an option value containing the result of reduceRight(op)
is this general iterable collection
is nonempty,
None
otherwise.
Optionally reuses an existing combiner for better performance.
Optionally reuses an existing combiner for better performance. By default it doesn't - subclasses may override this behaviour.
The provided combiner oldc
that can potentially be reused will be either some combiner from the previous computational task, or None
if there
was no previous phase (in which case this method must return newc
).
The combiner that is the result of the previous task, or None
if there was no previous task.
The new, empty combiner that can be used.
Either newc
or oldc
.
Returns new general sequence with elements in reversed order.
Returns new general sequence with elements in reversed order.
Note: will not terminate for infinite-sized collections.
A new general sequence with all elements of this general sequence in reversed order.
[use case] Builds a new collection by applying a function to all elements of this parallel array and collecting the results in reversed order.
Builds a new collection by applying a function to all elements of this parallel array and collecting the results in reversed order.
Note: will not terminate for infinite-sized collections.
Note: xs.reverseMap(f)
is the same as xs.reverse.map(f)
but might be more efficient.
the element type of the returned collection.
the function to apply to each element.
a new parallel array resulting from applying the given function
f
to each element of this parallel array and collecting the results in reversed order.
[use case] Checks if the other iterable collection contains the same elements in the same order as this parallel array.
Checks if the other iterable collection contains the same elements in the same order as this parallel array.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Note: will not terminate for infinite-sized collections.
the collection to compare with.
true
, if both collections contain the same elements in the same order, false
otherwise.
[use case] 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.
neutral element for the operator op
the associative operator for the scan
a new parallel array containing the prefix scan of the elements in this parallel array
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: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the actual type of the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
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
.
collection with intermediate results
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.
Example:
List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
the actual type of the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
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
.
collection with intermediate results
Returns the length of the longest segment of elements starting at a given position satisfying some predicate.
Returns the length of the longest segment of elements starting at a given position satisfying some predicate.
This method will use indexFlag
signalling capabilities. This means
that splitters may set and read the indexFlag
state.
The index flag is initially set to maximum integer value.
the predicate used to test the elements
the starting offset for the search
the length of the longest segment of elements starting at from
and
satisfying the predicate
The size of this general sequence.
The size of this general sequence.
Note: will not terminate for infinite-sized collections.
the number of elements in this general sequence.
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.
the lowest index to include from this general iterable collection .
the lowest index to EXCLUDE from this general iterable collection .
a general iterable collection
containing the elements greater than or equal to
index from
extending up to (but not including) index until
of this general iterable collection
.
Splits this general iterable collection into a prefix/suffix pair according to a predicate.
Splits this general iterable collection into a prefix/suffix pair according to a predicate.
This method will use indexFlag
signalling capabilities. This means
that splitters may set and read the indexFlag
state.
The index flag is initially set to maximum integer value.
the predicate used to test the elements
a pair consisting of the longest prefix of the collection for which all
the elements satisfy pred
, and the rest of the collection
Splits this general iterable collection into two at a given position.
Splits this general iterable collection
into two at a given position.
Note: c splitAt n
is equivalent to (but possibly more efficient than)
(c take n, c drop n)
.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the position at which to split.
a pair of general iterable collection
s consisting of the first n
elements of this general iterable collection
, and the other elements.
A more refined version of the iterator found in the ParallelIterable
trait,
this iterator can be split into arbitrary subsets of iterators.
A more refined version of the iterator found in the ParallelIterable
trait,
this iterator can be split into arbitrary subsets of iterators.
an iterator that can be split into subsets of precise size
Tests whether this general sequence contains the given sequence at a given index.
Tests whether this general sequence contains the given sequence at a given index.
This method will use abort
signalling capabilities. This means
that splitters may send and read abort
signals.
the element type of that
parallel sequence
the parallel sequence this sequence is being searched for
the starting offset for the search
true
if there is a sequence that
starting at offset
in this sequence, false
otherwise
Tests whether this general sequence starts with the given sequence.
Tests whether this general sequence starts with the given sequence.
the sequence to test
true
if this collection has that
as a prefix, false
otherwise.
Defines the prefix of this object's toString
representation.
Defines the prefix of this object's toString
representation.
a string representation which starts the result of toString
applied to this parallel iterable. By default the string prefix is the
simple name of the collection class parallel iterable.
[use case] Sums up the elements of this collection.
Sums up the elements of this collection.
the sum of all elements in this parallel array 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 parallel array and as result type of sum
.
Examples of such types are: Long
, Float
, Double
, BigInt
.
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.
a general iterable collection consisting of all elements of this general iterable collection
except the first one.
if the general iterable collection is empty.
Selects first n elements.
Selects first n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to take from this general iterable collection .
a general iterable collection
consisting only of the first n
elements of this general iterable collection
,
or else the whole general iterable collection
, if it has less than n
elements.
Takes the longest prefix of elements that satisfy the predicate.
Takes the longest prefix of elements that satisfy the predicate.
This method will use indexFlag
signalling capabilities. This means
that splitters may set and read the indexFlag
state.
The index flag is initially set to maximum integer value.
the predicate used to test the elements
the longest prefix of this general iterable collection
of elements that satisy the predicate pred
The task support object which is responsible for scheduling and load-balancing tasks to processors.
The task support object which is responsible for scheduling and load-balancing tasks to processors.
Changes the task support object which is responsible for scheduling and load-balancing tasks to processors.
Changes the task support object which is responsible for scheduling and load-balancing tasks to processors.
A task support object can be changed in a parallel collection after it has been created, but only during a quiescent period, i.e. while there are no concurrent invocations to parallel collection methods.
Here is a way to change the task support of a parallel collection:
import scala.collection.parallel._ val pc = mutable.ParArray(1, 2, 3) pc.tasksupport = new ForkJoinTaskSupport( new scala.concurrent.forkjoin.ForkJoinPool(2))
[use case] Converts this parallel array into another by copying all elements.
Converts this parallel array into another by copying all elements.
Note: will not terminate for infinite-sized collections.
The collection type to build.
a new collection containing all elements of this parallel array.
[use case] Converts this parallel array to an array.
Converts this parallel array to an array.
Note: will not terminate for infinite-sized collections.
an array containing all elements of this parallel array.
An ClassTag
must be available for the element type of this parallel array.
Uses the contents of this general iterable collection to create a new mutable buffer.
Uses the contents of this general iterable collection to create a new mutable buffer.
Note: will not terminate for infinite-sized collections.
a buffer containing all elements of this general iterable collection .
Converts this general iterable collection to an indexed sequence.
Converts this general iterable collection to an indexed sequence.
Note: will not terminate for infinite-sized collections.
an indexed sequence containing all elements of this general iterable collection .
Converts this parallel iterable to an iterable collection.
Converts this parallel iterable to an iterable collection. Note that
the choice of target Iterable
is lazy in this default implementation
as this TraversableOnce
may be lazy and unevaluated (i.e. it may
be an iterator which is only traversable once).
Note: will not terminate for infinite-sized collections.
an Iterable
containing all elements of this parallel iterable.
Returns an Iterator over the elements in this general iterable collection .
Returns an Iterator over the elements in this general iterable collection . Will return the same Iterator if this instance is already an Iterator.
Note: will not terminate for infinite-sized collections.
an Iterator containing all elements of this general iterable collection .
Converts this general iterable collection to a list.
Converts this general iterable collection to a list.
Note: will not terminate for infinite-sized collections.
a list containing all elements of this general iterable collection .
[use case] Converts this parallel array to a map.
Converts this parallel array 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.
Note: will not terminate for infinite-sized collections.
a map of type immutable.Map[T, U]
containing all key/value pairs of type (T, U)
of this parallel array.
Converts this mutable parallel sequence to a sequence.
Converts this mutable parallel sequence to a sequence. As with toIterable
, it's lazy
in this default implementation, as this TraversableOnce
may be
lazy and unevaluated.
Note: will not terminate for infinite-sized collections.
a sequence containing all elements of this mutable parallel sequence.
Converts this general iterable collection to a set.
Converts this general iterable collection to a set.
Note: will not terminate for infinite-sized collections.
a set containing all elements of this general iterable collection .
Converts this general iterable collection to a stream.
Converts this general iterable collection to a stream.
Note: will not terminate for infinite-sized collections.
a stream containing all elements of this general iterable collection .
Converts this general iterable collection to an unspecified Traversable.
Converts this general iterable collection to an unspecified Traversable. Will return the same collection if this instance is already Traversable.
Note: will not terminate for infinite-sized collections.
a Traversable containing all elements of this general iterable collection .
Converts this general iterable collection to a Vector.
Converts this general iterable collection to a Vector.
Note: will not terminate for infinite-sized collections.
a vector containing all elements of this general iterable collection .
Transposes this collection of traversable collections into a collection of collections.
Transposes this collection of traversable collections into a collection of collections.
The resulting collection's type will be guided by the static type of 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))
the type of the elements of each traversable collection.
an implicit conversion which asserts that the
element type of this collection is a Traversable
.
a two-dimensional collection of collections which has as nth row the nth column of this collection.
(Changed in version 2.9.0) transpose
throws an IllegalArgumentException
if collections are not uniformly sized.
if all collections in this collection are not of the same size.
[use case] Produces a new sequence which contains all elements of this parallel array and also all elements of a given sequence.
Produces a new sequence which contains all elements of this parallel array and also all elements of
a given sequence. xs union ys
is equivalent to xs ++ ys
.
Another way to express this
is that xs union ys
computes the order-presevring multi-set union of xs
and ys
.
union
is hence a counter-part of diff
and intersect
which also work on multi-sets.
Note: will not terminate for infinite-sized collections.
the sequence to add.
a new parallel array which contains all elements of this parallel array
followed by all elements of that
.
Converts this collection of pairs into two collections of the first and second half of each pair.
Converts this collection of pairs into two collections of the first and second half of each pair.
val xs = CC( (1, "one"), (2, "two"), (3, "three")).unzip // xs == (CC(1, 2, 3), // CC(one, two, three))
the type of the first half of the element pairs
the type of the second half of the element pairs
an implicit conversion which asserts that the element type of this collection is a pair.
a pair of collections, containing the first, respectively second half of each element pair of this collection.
Converts this collection of triples into three collections of the first, second, and third element of each triple.
Converts this collection of triples into three collections of the first, second, and third element of each triple.
val xs = CC( (1, "one", '1'), (2, "two", '2'), (3, "three", '3')).unzip3 // xs == (CC(1, 2, 3), // CC(one, two, three), // CC(1, 2, 3))
the type of the first member of the element triples
the type of the second member of the element triples
the type of the third member of the element triples
an implicit conversion which asserts that the element type of this collection is a triple.
a triple of collections, containing the first, second, respectively third member of each element triple of this collection.
[use case] A copy of this parallel array with one single replaced element.
A copy of this parallel array with one single replaced element.
the position of the replacement
the replacing element
a copy of this parallel array with the element at position index
replaced by elem
.
[use case] Returns a parallel array formed from this parallel array and another iterable collection by combining corresponding elements in pairs.
Returns a parallel array formed from this parallel array 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.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
a new parallel array containing pairs consisting of
corresponding elements of this parallel array and that
. The length
of the returned collection is the minimum of the lengths of this parallel array and that
.
[use case] Returns a parallel array formed from this parallel array and another iterable collection by combining corresponding elements in pairs.
Returns a parallel array formed from this parallel array 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.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
the element to be used to fill up the result if this parallel array is shorter than that
.
the element to be used to fill up the result if that
is shorter than this parallel array.
a new parallel array containing pairs consisting of
corresponding elements of this parallel array and that
. The length
of the returned collection is the maximum of the lengths of this parallel array and that
.
If this parallel array is shorter than that
, thisElem
values are used to pad the result.
If that
is shorter than this parallel array, thatElem
values are used to pad the result.
[use case] Zips this parallel array with its indices.
Zips this parallel array with its indices.
Note: might return different results for different runs, unless the underlying collection type is ordered.
A new parallel array containing pairs consisting of all elements of this
parallel array paired with their index. Indices start at 0
.
List("a", "b", "c").zipWithIndex = List(("a", 0), ("b", 1), ("c", 2))
(Since version 2.11.0) use .seq.view
Parallel sequence holding elements in a linear array.
ParArray
is a parallel sequence with a predefined size. The size of the array cannot be changed after it's been created.ParArray
internally keeps an array containing the elements. This means that bulk operations based on traversal ensure fast access to elements.ParArray
uses lazy builders that create the internal data array only after the size of the array is known. In the meantime, they keep the result set fragmented. The fragments are copied into the resulting data array in parallel using fast array copy operations once all the combiners are populated in parallel.type of the elements in the array
2.9
Scala's Parallel Collections Library overview section on
ParArray
for more information.