IterableOps

trait IterableOps[+A, +CC[X], +C] extends Any

Base trait for Iterable operations

VarianceNote

We require that for all child classes of Iterable the variance of the child class and the variance of the C parameter passed to IterableOps are the same. We cannot express this since we lack variance polymorphism. That's why we have to resort at some places to write C[A @uncheckedVariance].

CC: type constructor of the collection (e.g. List, Set). Operations returning a collection with a different type of element B (e.g. map) return a CC[B].
C: type of the collection (e.g. List[Int], String, BitSet). Operations returning a collection with the same type of element (e.g. drop, filter) return a C.

Linear Supertypes

Any

Known Subclasses

ArrayOps, ArrayView, BitSet, BitSetOps, IndexedSeq, IndexedSeqOps, IndexedView, Drop, DropRight, Map, Reverse, Take, TakeRight, Iterable, LinearSeq, LinearSeqOps, Map, MapOps, KeySet, Seq, SeqOps, Set, SetOps, SortedMap, SortedMapOps, KeySortedSet, SortedSet, SortedSetOps, StrictOptimizedIterableOps, StrictOptimizedSeqOps, StringOps, StringView, View, Append, Concat, DistinctBy, Drop, DropWhile, Elems, Empty, Fill, Filter, FilterKeys, FlatMap, Iterate, Map, MapValues, PadTo, Partitioned, Prepend, ScanLeft, Single, Tabulate, Take, TakeWhile, Updated, Zip, ZipWithIndex, Map, TrieMap, ::, BitSet, BitSet1, BitSet2, BitSetN, HashMap, HashMap1, HashTrieMap, HashSet, ImmutableArray, IndexedSeq, IndexedSeqOps, Iterable, LazyList, Cons, Empty, LinearSeq, LinearSeqOps, List, ListMap, Node, ListSet, Node, Map, Map1, Map2, Map3, Map4, SmallMap, MapOps, ImmutableKeySet, Nil, NumericRange, Range, Seq, SeqOps, Set, Set1, Set2, Set3, Set4, SmallSet, SetOps, SortedMap, SortedMapOps, ImmutableKeySortedSet, SortedSet, SortedSetOps, StrictOptimizedSeqOps, TreeMap, TreeSet, Vector, ArrayBuffer, ArrayBufferView, BitSet, HashMap, HashSet, IndexedOptimizedSeq, Iterable, IterableOps, LinkedHashMap, LinkedKeySet, LinkedHashSet, ListBuffer, Map, MapOps, Seq, SeqOps, Set, SetOps, SortedMap, SortedMapOps, SortedSet, SortedSetOps, TreeMap, TreeSet

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Inherited

IterableOps
Any

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Visibility

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Type Members

class WithFilter extends collection.WithFilter[A, CC]
A template trait that contains just the map, flatMap, foreach and withFilter methods of trait Iterable.

Abstract Value Members

abstract def coll: C
returns
This collection as a C.

Attributes
protected[this]
abstract def fromSpecificIterable(coll: Iterable[A]): C

Attributes
protected[this]
abstract def getClass(): Class[_]

Definition Classes
Any
abstract def iterableFactory: IterableFactoryLike[CC]
abstract def newSpecificBuilder(): Builder[A, C]
returns
a strict builder for the same collection type. Note that in the case of lazy collections (e.g. View or immutable.LazyList), it is possible to implement this method but the resulting Builder will break laziness. As a consequence, operations should preferably be implemented on top of views rather than builders.

Attributes
protected[this]
abstract def toIterable: Iterable[A]
returns
This collection as an Iterable[A]. No new collection will be built if this is already an Iterable[A].

Concrete Value Members

final def !=(arg0: Any): Boolean

Definition Classes
Any
final def ##(): Int

Definition Classes
Any
final def ++[B >: A](suffix: Iterable[B]): CC[B]
Alias for concat
Alias for concat

Annotations
@inline()
final def ==(arg0: Any): Boolean

Definition Classes
Any
final def asInstanceOf[T0]: T0

Definition Classes
Any
def className: String
The class name of this collection.
The class name of this collection. To be used for converting to string. Collections generally print like this:
<className>(elem_1, ..., elem_n)
def collect[B](pf: PartialFunction[A, B]): CC[B]
def collectFirst[B](pf: PartialFunction[A, B]): Option[B]
Finds the first element of the $coll for which the given partial function is defined, and applies the partial function to it.
Finds the first element of the $coll for which the given partial function is defined, and applies the partial function to it.
$mayNotTerminateInf $orderDependent
pf
the partial function
returns
an option value containing pf applied to the first value for which it is defined, or None if none exists.
Example:
1. Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
final def concat[B >: A](suffix: Iterable[B]): CC[B]

Annotations
@inline()
def copyToArray[B >: A](xs: Array[B], start: Int = 0): xs.type
Copy all elements of this collection to array xs, starting at start.
def count(p: (A) ⇒ Boolean): Int
Counts the number of elements in the $coll which satisfy a predicate.
Counts the number of elements in the $coll which satisfy a predicate.
p
the predicate used to test elements.
returns
the number of elements satisfying the predicate p.
def drop(n: Int): C
The rest of the collection without its n first elements.
The rest of the collection without its n first elements. For linear, immutable collections this should avoid making a copy.
def dropRight(n: Int): C
The rest of the collection without its n last elements.
The rest of the collection without its n last elements. For linear, immutable collections this should avoid making a copy.
def dropWhile(p: (A) ⇒ Boolean): C
Skips longest sequence of elements of this iterator which satisfy given predicate p, and returns an iterator of the remaining elements.
Skips longest sequence of elements of this iterator which satisfy given predicate p, and returns an iterator of the remaining elements.
p
the predicate used to skip elements.
returns
an iterator consisting of the remaining elements

Note
Reuse: $consumesAndProducesIterator
def equals(arg0: Any): Boolean

Definition Classes
Any
def exists(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for at least one element of this $coll.
Tests whether a predicate holds for at least one element of this $coll.
$mayNotTerminateInf
p
the predicate used to test elements.
returns
true if the given predicate p is satisfied by at least one element of this $coll, otherwise false
def filter(pred: (A) ⇒ Boolean): C
Selects all elements of this $coll which satisfy a predicate.
Selects all elements of this $coll which satisfy a predicate.
pred
the predicate used to test elements.
returns
a new $coll consisting of all elements of this $coll that satisfy the given predicate pred. Their order may not be preserved.
def filterNot(pred: (A) ⇒ Boolean): C
Selects all elements of this $coll which do not satisfy a predicate.
Selects all elements of this $coll which do not satisfy a predicate.
pred
the predicate used to test elements.
returns
a new $coll consisting of all elements of this $coll that do not satisfy the given predicate pred. Their order may not be preserved.
def find(p: (A) ⇒ Boolean): Option[A]
Finds the first element of the $coll satisfying a predicate, if any.
Finds the first element of the $coll satisfying a predicate, if any.
$mayNotTerminateInf $orderDependent
p
the predicate used to test elements.
returns
an option value containing the first element in the $coll that satisfies p, or None if none exists.
def flatMap[B](f: (A) ⇒ IterableOnce[B]): CC[B]
Flatmap
def flatten[B](implicit ev: (A) ⇒ IterableOnce[B]): CC[B]
def foldLeft[B](z: B)(op: (B, A) ⇒ B): B
Fold left
def foldRight[B](z: B)(op: (A, B) ⇒ B): B
Fold right
def forall(p: (A) ⇒ Boolean): Boolean
Tests whether a predicate holds for all elements of this $coll.
Tests whether a predicate holds for all elements of this $coll.
$mayNotTerminateInf
p
the predicate used to test elements.
returns
true if this $coll is empty or the given predicate p holds for all elements of this $coll, otherwise false.
def foreach[U](f: (A) ⇒ U): Unit
Apply f to each element for its side effects Note: [U] parameter needed to help scalac's type inference.
def fromIterable[E](it: Iterable[E]): CC[E]

Attributes
protected[this]
def groupBy[K](f: (A) ⇒ K): immutable.Map[K, C]
Partitions this $coll into a map of ${coll}s according to some discriminator function.
Partitions this $coll into a map of ${coll}s according to some discriminator function.
Note: When applied to a view or a lazy collection it will always force the elements.
K
the type of keys returned by the discriminator function.
f
the discriminator function.
returns
A map from keys to ${coll}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 $coll of those elements x for which f(x) equals k.
def groupMap[K, B](key: (A) ⇒ K)(f: (A) ⇒ B): immutable.Map[K, CC[B]]
Partitions this $coll into a map of ${coll}s according to a discriminator function key.
Partitions this $coll into a map of ${coll}s 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)
```
K
the type of keys returned by the discriminator function
B
the type of values returned by the transformation function
key
the discriminator function
f
the element transformation function
def groupMapReduce[K, B](key: (A) ⇒ K)(f: (A) ⇒ B)(reduce: (B, B) ⇒ B): immutable.Map[K, B]
Partitions this $coll into a map according to a discriminator function key.
Partitions this $coll into a map according to a discriminator function key. All the values that have the same discriminator are then transformed by the value 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)(_ + _)
```
def grouped(size: Int): Iterator[C]
Partitions elements in fixed size ${coll}s.
Partitions elements in fixed size ${coll}s.
size
the number of elements per group
returns
An iterator producing ${coll}s 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
def hashCode(): Int

Definition Classes
Any
def head: A
The first element of the collection.
def init: C
The initial part of the collection without its last element.
def isEmpty: Boolean
Is the collection empty?
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
def knownSize: Int
The number of elements in this collection, if it can be cheaply computed, -1 otherwise.
The number of elements in this collection, if it can be cheaply computed, -1 otherwise. Cheaply usually means: Not requiring a collection traversal.
def last: A
Selects the last element.
Selects the last element. $orderDependent
returns
The last element of this $coll.

Exceptions thrown
NoSuchElementException If the $coll is empty.
def lastOption: Option[A]
Optionally selects the last element.
Optionally selects the last element. $orderDependent
returns
the last element of this $coll$ if it is nonempty, None if it is empty.
def map[B](f: (A) ⇒ B): CC[B]
Builds a new collection by applying a function to all elements of this $coll.
Builds a new collection by applying a function to all elements of this $coll.
B
the element type of the returned collection.
f
the function to apply to each element.
returns
a new $coll resulting from applying the given function f to each element of this $coll and collecting the results.
def max: A
[use case] Finds the largest element.
[use case]
Finds the largest element.
returns
the largest element of this $coll.

Full Signature
def max[B >: A](implicit ord: Ordering[B]): A
def maxBy[B](f: (A) ⇒ B): A
[use case] Finds the first element which yields the largest value measured by function f.
[use case]
Finds the first element which yields the largest value measured by function f.
B
The result type of the function f.
f
The measuring function.
returns
the first element of this $coll with the largest value measured by function f.

Full Signature
def maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
def min: A
[use case] Finds the smallest element.
[use case]
Finds the smallest element.
returns
the smallest element of this $coll

Full Signature
def min[B >: A](implicit ord: Ordering[B]): A
def minBy[B](f: (A) ⇒ B): A
[use case] Finds the first element which yields the smallest value measured by function f.
[use case]
Finds the first element which yields the smallest value measured by function f.
B
The result type of the function f.
f
The measuring function.
returns
the first element of this $coll with the smallest value measured by function f.

Full Signature
def minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A
def mkString: String
def mkString(sep: String): String
def mkString(start: String, sep: String, end: String): String
A string showing all elements of this collection, separated by string sep.
def nonEmpty: Boolean
Is the collection not empty?
def partition(p: (A) ⇒ Boolean): (C, C)
A pair of, first, all elements that satisfy prediacte p and, second, all elements that do not.
A pair of, first, all elements that satisfy prediacte 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 Buildable, which requires only a single traversal.
def product: A
[use case] Multiplies up the elements of this collection.
[use case]
Multiplies up the elements of this collection.
returns
the product of all elements in this $coll 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 $coll and as result type of product. Examples of such types are: Long, Float, Double, BigInt.

Full Signature
def product[B >: A](implicit num: Numeric[B]): B
def reduce[B >: A](op: (B, B) ⇒ B): B
Reduces the elements of this $coll using the specified associative binary operator.
Reduces the elements of this $coll using the specified associative binary operator.
$undefinedorder
B
A type parameter for the binary operator, a supertype of A.
op
A binary operator that must be associative.
returns
The result of applying reduce operator op between all the elements if the $coll is nonempty.

Exceptions thrown
UnsupportedOperationException if this $coll is empty.
def reduceLeft[B >: A](op: (B, A) ⇒ B): B
Applies a binary operator to all elements of this $coll, going left to right.
Applies a binary operator to all elements of this $coll, going left to right. $willNotTerminateInf $orderDependentFold
B
the result type of the binary operator.
op
the binary operator.
returns
the result of inserting op between consecutive elements of this $coll, going left to right:
```
op( op( ... op(x_1, x_2) ..., x_{n-1}), x_n)
```
where x₁, ..., x_n are the elements of this $coll.
Exceptions thrown
UnsupportedOperationException if this $coll is empty.
def reduceLeftOption[B >: A](op: (B, A) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this $coll, going left to right.
Optionally applies a binary operator to all elements of this $coll, going left to right. $willNotTerminateInf $orderDependentFold
B
the result type of the binary operator.
op
the binary operator.
returns
an option value containing the result of reduceLeft(op) if this $coll is nonempty, None otherwise.
def reduceOption[B >: A](op: (B, B) ⇒ B): Option[B]
Reduces the elements of this $coll, if any, using the specified associative binary operator.
Reduces the elements of this $coll, if any, using the specified associative binary operator.
$undefinedorder
B
A type parameter for the binary operator, a supertype of A.
op
A binary operator that must be associative.
returns
An option value containing result of applying reduce operator op between all the elements if the collection is nonempty, and None otherwise.
def reduceRight[B >: A](op: (A, B) ⇒ B): B
Applies a binary operator to all elements of this $coll, going right to left.
Applies a binary operator to all elements of this $coll, going right to left. $willNotTerminateInf $orderDependentFold
B
the result type of the binary operator.
op
the binary operator.
returns
the result of inserting op between consecutive elements of this $coll, going right to left:
```
op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
```
where x₁, ..., x_n are the elements of this $coll.
Exceptions thrown
UnsupportedOperationException if this $coll is empty.
def reduceRightOption[B >: A](op: (A, B) ⇒ B): Option[B]
Optionally applies a binary operator to all elements of this $coll, going right to left.
Optionally applies a binary operator to all elements of this $coll, going right to left. $willNotTerminateInf $orderDependentFold
B
the result type of the binary operator.
op
the binary operator.
returns
an option value containing the result of reduceRight(op) if this $coll is nonempty, None otherwise.
def reversed: Iterable[A]

Attributes
protected[this]
def scan[B >: A](z: B)(op: (B, B) ⇒ B): CC[B]
Computes a prefix scan of the elements of the collection.
Computes a prefix scan of the elements of the collection.
Note: The neutral element z may be applied more than once.
B
element type of the resulting collection
z
neutral element for the operator op
op
the associative operator for the scan
returns
a new $coll containing the prefix scan of the elements in this $coll
def scanLeft[B](z: B)(op: (B, A) ⇒ B): CC[B]
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.
$willNotTerminateInf $orderDependent
B
the type of the elements in the resulting collection
z
the initial value
op
the binary operator applied to the intermediate result and the element
returns
collection with intermediate results
def scanRight[B](z: B)(op: (A, B) ⇒ B): CC[B]
Produces a collection containing cumulative results of applying the operator going right to left.
Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result. $willNotTerminateInf $orderDependent
Example:
```
List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
```
B
the type of the elements in the resulting collection
z
the initial value
op
the binary operator applied to the intermediate result and the element
returns
collection with intermediate results
def size: Int
The number of elements in this collection.
The number of elements in this collection. Does not terminate for infinite collections.
def slice(from: Int, until: Int): C
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
```
$orderDependent
from
the lowest index to include from this $coll.
until
the lowest index to EXCLUDE from this $coll.
returns
a $coll containing the elements greater than or equal to index from extending up to (but not including) index until of this $coll.
def sliding(size: Int, step: Int): Iterator[C]
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
size
the number of elements per group
step
the distance between the first elements of successive groups
returns
An iterator producing ${coll}s of size size, except the last element (which may be the only element) will be truncated if there are fewer than size elements remaining to be grouped.

See also
scala.collection.Iterator, method sliding
def sliding(size: Int): Iterator[C]
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.) The "sliding window" step is set to one.
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.) The "sliding window" step is set to one.
size
the number of elements per group
returns
An iterator producing ${coll}s of size size, except the last element (which may be the only element) will be truncated if there are fewer than size elements remaining to be grouped.

See also
scala.collection.Iterator, method sliding
def span(p: (A) ⇒ Boolean): (C, C)
Splits this $coll into a prefix/suffix pair according to a predicate.
Splits this $coll 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. $orderDependent
p
the test predicate
returns
a pair consisting of the longest prefix of this $coll whose elements all satisfy p, and the rest of this $coll.
def splitAt(n: Int): (C, C)
Splits this $coll into two at a given position.
Splits this $coll into two at a given position. Note: c splitAt n is equivalent to (but possibly more efficient than) (c take n, c drop n). $orderDependent
n
the position at which to split.
returns
a pair of ${coll}s consisting of the first n elements of this $coll, and the other elements.
def sum: A
[use case] Sums up the elements of this collection.
[use case]
Sums up the elements of this collection.
returns
the sum of all elements in this $coll 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 $coll and as result type of sum. Examples of such types are: Long, Float, Double, BigInt.

Full Signature
def sum[B >: A](implicit num: Numeric[B]): B
def tail: C
The rest of the collection without its first element.
def take(n: Int): C
A collection containing the first n elements of this collection.
def takeRight(n: Int): C
A collection containing the last n elements of this collection.
def takeWhile(p: (A) ⇒ Boolean): C
Takes longest prefix of elements that satisfy a predicate.
Takes longest prefix of elements that satisfy a predicate. $orderDependent
p
The predicate used to test elements.
returns
the longest prefix of this $coll whose elements all satisfy the predicate p.
def to[C1](factory: Factory[A, C1]): C1
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]
def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]
Convert collection to array.
def toString(): String

Definition Classes
IterableOps → Any
def unzip[A1, A2](implicit asPair: <:<[A, (A1, A2)]): (CC[A1], CC[A2])
Converts this $coll of pairs into two collections of the first and second half of each pair.
Converts this $coll of pairs into two collections of the first and second half of each pair.
```
val xs = $Coll(
           (1, "one"),
           (2, "two"),
           (3, "three")).unzip
// xs == ($Coll(1, 2, 3),
//        $Coll(one, two, three))
```
A1
the type of the first half of the element pairs
A2
the type of the second half of the element pairs
asPair
an implicit conversion which asserts that the element type of this $coll is a pair.
returns
a pair of ${coll}s, containing the first, respectively second half of each element pair of this $coll.
def view: View[A]
A view representing the elements of this collection.
def withFilter(p: (A) ⇒ Boolean): collection.WithFilter[A, CC]
Creates a non-strict filter of this $coll.
Creates a non-strict filter of this $coll.
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. $orderDependent
p
the predicate used to test elements.
returns
an object of class WithFilter, which supports map, flatMap, foreach, and withFilter operations. All these operations apply to those elements of this $coll which satisfy the predicate p.
def zip[B](xs: Iterable[B]): CC[(A, B)]
Returns a $coll formed from this $coll and another iterable collection by combining corresponding elements in pairs.
Returns a $coll formed from this $coll 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.
B
the type of the second half of the returned pairs
xs
The iterable providing the second half of each result pair
returns
a new collection of type That containing pairs consisting of corresponding elements of this $coll and that. The length of the returned collection is the minimum of the lengths of this $coll and that.
def zipWithIndex: CC[(A, Int)]
Zips this $coll with its indices.
Zips this $coll with its indices.
returns
A new collection of type That containing pairs consisting of all elements of this $coll paired with their index. Indices start at 0.
Example:
1. List("a", "b", "c").zipWithIndex == List(("a", 0), ("b", 1), ("c", 2))

Packages

IterableOps

trait IterableOps[+A, +CC[X], +C] extends Any

Type Members

Abstract Value Members

Concrete Value Members

def max[B >: A](implicit ord: Ordering[B]): A

def maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

def min[B >: A](implicit ord: Ordering[B]): A

def minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

def product[B >: A](implicit num: Numeric[B]): B

def sum[B >: A](implicit num: Numeric[B]): B

Inherited from Any

Ungrouped

Packages

IterableOps 

trait IterableOps[+A, +CC[X], +C] extends Any

Type Members

Abstract Value Members

Concrete Value Members

def max[B >: A](implicit ord: Ordering[B]): A

def maxBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

def min[B >: A](implicit ord: Ordering[B]): A

def minBy[B](f: (A) ⇒ B)(implicit cmp: Ordering[B]): A

def product[B >: A](implicit num: Numeric[B]): B

def sum[B >: A](implicit num: Numeric[B]): B

Inherited from Any

Ungrouped

IterableOps