Trait scala.collection.IterableOps

trait IterableOps[+A, +CC[_], +C] extends IterableOnce[A] with IterableOnceOps[A, CC, C]

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.

Source
Iterable.scala
Linear Supertypes
IterableOnceOps[A, CC, C], IterableOnce[A], Any
Known Subclasses
ValueSet, AbstractIndexedSeqView, AbstractIterable, AbstractMap, AbstractMapView, AbstractSeq, AbstractSeqView, AbstractSet, AbstractView, BitSet, BitSetOps, EvidenceIterableFactoryDefaults, IndexedSeq, IndexedSeqOps, IndexedSeqView, Appended, Concat, Drop, DropRight, Id, Map, Prepended, Reverse, Slice, Take, TakeRight, Iterable, IterableFactoryDefaults, LinearSeq, LinearSeqOps, Map, MapFactoryDefaults, MapOps, KeySet, MapView, Filter, FilterKeys, Id, MapValues, TapEach, Seq, SeqMap, SeqOps, SeqView, Appended, Concat, Drop, DropRight, Id, Map, Prepended, Reverse, Sorted, Take, TakeRight, Set, SetOps, SortedMap, SortedMapFactoryDefaults, SortedMapOps, KeySortedSet, SortedSet, SortedSetFactoryDefaults, SortedSetOps, StrictOptimizedIterableOps, StrictOptimizedLinearSeqOps, StrictOptimizedMapOps, StrictOptimizedSeqOps, StrictOptimizedSetOps, StrictOptimizedSortedMapOps, StrictOptimizedSortedSetOps, StringView, View, Appended, Collect, Concat, DistinctBy, Drop, DropRight, DropWhile, Elems, Empty, Fill, Filter, FlatMap, Iterate, LeftPartitionMapped, Map, PadTo, Prepended, RightPartitionMapped, ScanLeft, Single, Tabulate, Take, TakeRight, TakeWhile, Unfold, Updated, Zip, ZipAll, ZipWithIndex, Map, TrieMap, ::, AbstractMap, AbstractSeq, AbstractSet, ArraySeq, ofBoolean, ofByte, ofChar, ofDouble, ofFloat, ofInt, ofLong, ofRef, ofShort, ofUnit, BitSet, HashMap, HashSet, IndexedSeq, IndexedSeqOps, IntMap, Iterable, LazyList, LinearSeq, LinearSeqOps, List, ListMap, ListSet, Node, LongMap, Map, Map1, Map2, Map3, Map4, WithDefault, MapOps, ImmutableKeySet, Nil, NumericRange, Exclusive, Inclusive, Queue, Range, Exclusive, Inclusive, Seq, SeqMap, SeqOps, Set, Set1, Set2, Set3, Set4, SetOps, SortedMap, WithDefault, SortedMapOps, ImmutableKeySortedSet, SortedSet, SortedSetOps, Cons, Empty, StrictOptimizedMapOps, StrictOptimizedSeqOps, StrictOptimizedSetOps, StrictOptimizedSortedMapOps, StrictOptimizedSortedSetOps, TreeMap, TreeSeqMap, TreeSet, Vector, VectorMap, WrappedString, AbstractBuffer, AbstractIterable, AbstractMap, AbstractSeq, AbstractSet, AnyRefMap, ArrayBuffer, ArrayBufferView, ArrayDeque, ArrayDequeOps, ArraySeq, ofBoolean, ofByte, ofChar, ofDouble, ofFloat, ofInt, ofLong, ofRef, ofShort, ofUnit, BitSet, Buffer, CollisionProofHashMap, HashMap, HashSet, IndexedBuffer, IndexedSeq, IndexedSeqOps, Iterable, LinkedHashMap, LinkedKeySet, LinkedHashSet, ListBuffer, LongMap, Map, WithDefault, MapOps, MultiMap, PriorityQueue, Queue, Seq, SeqMap, SeqOps, Set, SetOps, SortedMap, WithDefault, SortedMapOps, SortedSet, SortedSetOps, Stack, StringBuilder, TreeMap, TreeSet, UnrolledBuffer, WeakHashMap, Accumulator, AnyAccumulator, DoubleAccumulator, IntAccumulator, LongAccumulator, SystemProperties, DefaultMap, BitSet1, BitSet2, BitSetN, Stream, ListMap, OpenHashMap

Abstract Value Members

abstract def coll: C

returns

This collection as a C.

Attributes
protected

abstract def fromSpecific(coll: IterableOnce[A]): C

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
protected
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 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.

abstract def getClass(): Class[_ <: AnyRef]

Returns the runtime class representation of the object.

returns

a class object corresponding to the runtime type of the receiver.

Definition Classes
Any

abstract def iterableFactory: IterableFactory[CC]

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

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).

abstract def iterator: Iterator[A]

Iterator can be used only once

Definition Classes
IterableOnce

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 with fromSpecific instead of this method.

Attributes
protected
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 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.

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

Test two objects for inequality.

returns

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

Definition Classes
Any

final def ##(): Int

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

returns

a hash value consistent with ==

Definition Classes
Any

def +(other: String): String

Implicit
This member is added by an implicit conversion from IterableOps[A, CC, C] toany2stringadd[IterableOps[A, CC, C]] performed by method any2stringadd in scala.Predef.
Definition Classes
any2stringadd

final def ++[B >: A](suffix: IterableOnce[B]): CC[B]

Alias for concat

Annotations
@inline()

def ->[B](y: B): (IterableOps[A, CC, C], B)

Implicit
This member is added by an implicit conversion from IterableOps[A, CC, C] toArrowAssoc[IterableOps[A, CC, C]] performed by method ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc
Annotations
@inline()

final def ==(arg0: Any): Boolean

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

returns

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

Definition Classes
Any

final def addString(b: mutable.StringBuilder): mutable.StringBuilder

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
b

the string builder to which elements are appended.

returns

the string builder b to which elements were appended.

Definition Classes
IterableOnceOps
Annotations
@inline()

final def addString(b: mutable.StringBuilder, sep: String): mutable.StringBuilder

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
b

the string builder to which elements are appended.

sep

the separator string.

returns

the string builder b to which elements were appended.

Definition Classes
IterableOnceOps
Annotations
@inline()

def addString(b: mutable.StringBuilder, start: String, sep: String, end: String): mutable.StringBuilder

Appends all elements of this collection 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 collection 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)
b

the string builder to which elements are appended.

start

the starting string.

sep

the separator string.

end

the ending string.

returns

the string builder b to which elements were appended.

Definition Classes
IterableOnceOps

final def asInstanceOf[T0]: T0

Cast the receiver object to be of type T0.

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

returns

the receiver object.

Definition Classes
Any
Exceptions thrown

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

def collect[B](pf: PartialFunction[A, B]): CC[B]

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

B

the element type of the returned iterable collection.

pf

the partial function which filters and maps the iterable collection.

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.

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

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

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.

pf

the partial function

returns

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

Definition Classes
IterableOnceOps
Example:

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

def concat[B >: A](suffix: IterableOnce[B]): CC[B]

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.

B

the element type of the returned collection.

suffix

the traversable to append.

returns

a new iterable collection which contains all elements of this iterable collection followed by all elements of suffix.

def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Int

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.

B

the type of the elements of the array.

xs

the array to fill.

start

the starting index of xs.

len

the maximal number of elements to copy.

returns

the number of elements written to the array

Definition Classes
IterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change. Note: will not terminate for infinite-sized collections.

def copyToArray[B >: A](xs: Array[B], start: Int): Int

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.

B

the type of the elements of the array.

xs

the array to fill.

start

the starting index of xs.

returns

the number of elements written to the array Note: will not terminate for infinite-sized collections.

Definition Classes
IterableOnceOps

def copyToArray[B >: A](xs: Array[B]): Int

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.

B

the type of the elements of the array.

xs

the array to fill.

returns

the number of elements written to the array Note: will not terminate for infinite-sized collections.

Definition Classes
IterableOnceOps

def corresponds[B](that: IterableOnce[B])(p: (A, B) => Boolean): Boolean

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

B

the type of the elements of that

that

the other collection

p

the test predicate, which relates elements from both collections

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

Definition Classes
IterableOnceOps

def count(p: (A) => Boolean): Int

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

p

the predicate used to test elements.

returns

the number of elements satisfying the predicate p.

Definition Classes
IterableOnceOps

def drop(n: Int): C

Selects all elements except first n ones.

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

n

the number of elements to drop from this iterable collection.

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.

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

def dropRight(n: Int): C

Selects all elements except last n ones.

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

n

the number of elements to drop from this iterable collection.

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.

def dropWhile(p: (A) => Boolean): C

Drops longest prefix of elements that satisfy a predicate.

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

p

The predicate used to test elements.

returns

the longest suffix of this iterable collection whose first element does not satisfy the predicate p.

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

def empty: C

The empty iterable of the same type as this iterable

returns

an empty iterable of type C.

def ensuring(cond: (IterableOps[A, CC, C]) => Boolean, msg: => Any): IterableOps[A, CC, C]

Implicit
This member is added by an implicit conversion from IterableOps[A, CC, C] toEnsuring[IterableOps[A, CC, C]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def ensuring(cond: (IterableOps[A, CC, C]) => Boolean): IterableOps[A, CC, C]

Implicit
This member is added by an implicit conversion from IterableOps[A, CC, C] toEnsuring[IterableOps[A, CC, C]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def ensuring(cond: Boolean, msg: => Any): IterableOps[A, CC, C]

Implicit
This member is added by an implicit conversion from IterableOps[A, CC, C] toEnsuring[IterableOps[A, CC, C]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def ensuring(cond: Boolean): IterableOps[A, CC, C]

Implicit
This member is added by an implicit conversion from IterableOps[A, CC, C] toEnsuring[IterableOps[A, CC, C]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def equals(arg0: Any): Boolean

Compares the receiver object (this) with the argument object (that) for equivalence.

Any implementation of this method should be an equivalence relation:

    It is reflexive: for any instance x of type Any, x.equals(x) should return true.It is symmetric: for any instances x and y of type Any, x.equals(y) should return true if and only if y.equals(x) returns true.It is transitive: for any instances x, y, and z of type Any if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.

If you override this method, you should verify that your implementation remains an equivalence relation. Additionally, when overriding this method it is usually necessary to override hashCode to ensure that objects which are "equal" (o1.equals(o2) returns true) hash to the same scala.Int. (o1.hashCode.equals(o2.hashCode)).

returns

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

Definition Classes
Any

def exists(p: (A) => Boolean): Boolean

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

Note: may not terminate for infinite-sized collections.

p

the predicate used to test elements.

returns

true if the given predicate p is satisfied by at least one element of this collection, otherwise false

Definition Classes
IterableOnceOps

def filter(pred: (A) => Boolean): C

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

returns

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

Definition Classes
IterableOpsIterableOnceOps

def filterNot(pred: (A) => Boolean): C

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

pred

the predicate used to test elements.

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.

Definition Classes
IterableOpsIterableOnceOps

def find(p: (A) => Boolean): Option[A]

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.

p

the predicate used to test elements.

returns

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

Definition Classes
IterableOnceOps

def flatMap[B](f: (A) => IterableOnce[B]): CC[B]

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)
B

the element type of the returned collection.

f

the function to apply to each element.

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.

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

def flatten[B](implicit asIterable: (A) => IterableOnce[B]): CC[B]

Converts this iterable collection of traversable collections into a iterable collection formed by the elements of these traversable 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)
B

the type of the elements of each traversable collection.

asIterable

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

returns

a new iterable collection resulting from concatenating all element iterable collections.

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

def fold[A1 >: A](z: A1)(op: (A1, A1) => A1): A1

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.

A1

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

z

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

op

a binary operator that must be associative.

returns

the result of applying the fold operator op between all the elements and z, or z if this collection is empty.

Definition Classes
IterableOnceOps

def foldLeft[B](z: B)(op: (B, A) => B): B

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.

B

the result type of the binary operator.

z

the start value.

op

the binary operator.

returns

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

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

where x1, ..., xn are the elements of this collection. Returns z if this collection is empty.

Definition Classes
IterableOnceOps

def foldRight[B](z: B)(op: (A, B) => B): B

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.

B

the result type of the binary operator.

z

the start value.

op

the binary operator.

returns

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

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

where x1, ..., xn are the elements of this collection. Returns z if this collection is empty.

Definition Classes
IterableOnceOps

def forall(p: (A) => Boolean): Boolean

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

Note: may not terminate for infinite-sized collections.

p

the predicate used to test elements.

returns

true if this collection is empty or the given predicate p holds for all elements of this collection, otherwise false.

Definition Classes
IterableOnceOps

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.

Definition Classes
IterableOnceOps

def formatted(fmtstr: String): String

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

Implicit
This member is added by an implicit conversion from IterableOps[A, CC, C] toStringFormat[IterableOps[A, CC, C]] performed by method StringFormat in scala.Predef.
Definition Classes
StringFormat
Annotations
@inline()

def groupBy[K](f: (A) => K): immutable.Map[K, C]

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.

K

the type of keys returned by the discriminator function.

f

the discriminator function.

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.

def groupMap[K, B](key: (A) => K)(f: (A) => B): immutable.Map[K, CC[B]]

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.

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 iterable collection 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)(_ + _)

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

def grouped(size: Int): Iterator[C]

Partitions elements in fixed size iterable collections.

size

the number of elements per group

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

def hashCode(): Int

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.

returns

the hash code value for this object.

Definition Classes
Any

Selects the first element of this iterable collection.

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

returns

the first element of this iterable collection.

Exceptions thrown

NoSuchElementException if the iterable collection is empty.

def headOption: Option[A]

Optionally selects the first element.

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

returns

the first element of this iterable collection if it is nonempty, None if it is empty.

def init: C

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.

def inits: Iterator[C]

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.

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)

def isEmpty: Boolean

Tests whether the collection is empty.

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

returns

true if the collection contains no elements, false otherwise.

Definition Classes
IterableOnceOps

final def isInstanceOf[T0]: Boolean

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

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

returns

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

Definition Classes
Any

def isTraversableAgain: Boolean

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

returns

true if it is repeatedly traversable, false otherwise.

Definition Classes
IterableOpsIterableOnceOps

def knownSize: Int

returns

The number of elements in this collection, if it can be cheaply computed, -1 otherwise. Cheaply usually means: Not requiring a collection traversal.

Definition Classes
IterableOnce

def last: A

Selects the last element.

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

returns

The last element of this iterable collection.

Exceptions thrown

NoSuchElementException If the iterable collection is empty.

def lastOption: Option[A]

Optionally selects the last element.

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

returns

the last element of this iterable collection$ if it is nonempty, None if it is empty.

def map[B](f: (A) => B): CC[B]

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

B

the element type of the returned iterable collection.

f

the function to apply to each element.

returns

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

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

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

Finds the largest element.

B

The type over which the ordering is defined.

ord

An ordering to be used for comparing elements.

returns

the largest element of this collection with respect to the ordering ord.

Definition Classes
IterableOnceOps
Exceptions thrown

UnsupportedOperationException if this collection is empty.

def maxBy[B](f: (A) => B)(implicit cmp: math.Ordering[B]): A

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.

cmp

An ordering to be used for comparing elements.

returns

the first element of this collection with the largest value measured by function f with respect to the ordering cmp.

Definition Classes
IterableOnceOps
Exceptions thrown

UnsupportedOperationException if this collection is empty.

def maxByOption[B](f: (A) => B)(implicit cmp: math.Ordering[B]): Option[A]

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.

cmp

An ordering to be used for comparing elements.

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.

Definition Classes
IterableOnceOps

def maxOption[B >: A](implicit ord: math.Ordering[B]): Option[A]

Finds the largest element.

B

The type over which the ordering is defined.

ord

An ordering to be used for comparing elements.

returns

an option value containing the largest element of this collection with respect to the ordering ord.

Definition Classes
IterableOnceOps

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

Finds the smallest element.

B

The type over which the ordering is defined.

ord

An ordering to be used for comparing elements.

returns

the smallest element of this collection with respect to the ordering ord.

Definition Classes
IterableOnceOps
Exceptions thrown

UnsupportedOperationException if this collection is empty.

def minBy[B](f: (A) => B)(implicit cmp: math.Ordering[B]): A

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.

cmp

An ordering to be used for comparing elements.

returns

the first element of this collection with the smallest value measured by function f with respect to the ordering cmp.

Definition Classes
IterableOnceOps
Exceptions thrown

UnsupportedOperationException if this collection is empty.

def minByOption[B](f: (A) => B)(implicit cmp: math.Ordering[B]): Option[A]

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.

cmp

An ordering to be used for comparing elements.

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.

Definition Classes
IterableOnceOps

def minOption[B >: A](implicit ord: math.Ordering[B]): Option[A]

Finds the smallest element.

B

The type over which the ordering is defined.

ord

An ordering to be used for comparing elements.

returns

an option value containing the smallest element of this collection with respect to the ordering ord.

Definition Classes
IterableOnceOps

final def mkString: String

Displays all elements of this collection in a string.

Delegates to addString, which can be overridden.

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.

Definition Classes
IterableOnceOps
Annotations
@inline()

final def mkString(sep: String): String

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

Delegates to addString, which can be overridden.

sep

the separator string.

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.

Definition Classes
IterableOnceOps
Annotations
@inline()
Example:

    List(1, 2, 3).mkString("|") = "1|2|3"

final def mkString(start: String, sep: String, end: String): String

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

Delegates to addString, which can be overridden.

start

the starting string.

sep

the separator string.

end

the ending string.

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.

Definition Classes
IterableOnceOps
Example:

    List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"

def nonEmpty: Boolean

Tests whether the collection is not empty.

returns

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

Definition Classes
IterableOnceOps
Annotations
@deprecatedOverriding("nonEmpty is defined as !isEmpty; override isEmpty instead", "2.13.0")

def partition(p: (A) => Boolean): (C, C)

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.

def partitionMap[A1, A2](f: (A) => Either[A1, A2]): (CC[A1], CC[A2])

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))
A1

the element type of the first resulting collection

A2

the element type of the second resulting collection

f

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

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.

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

Multiplies up the elements of this collection.

B

the result type of the * operator.

num

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

returns

the product of all elements of this collection with respect to the * operator in num.

Definition Classes
IterableOnceOps

def reduce[B >: A](op: (B, B) => B): B

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.

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 collection is nonempty.

Definition Classes
IterableOnceOps
Exceptions thrown

UnsupportedOperationException if this collection is empty.

def reduceLeft[B >: A](op: (B, A) => B): B

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.

B

the result type of the binary operator.

op

the binary operator.

returns

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

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

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

Definition Classes
IterableOnceOps
Exceptions thrown

UnsupportedOperationException if this collection is empty.

def reduceLeftOption[B >: A](op: (B, A) => B): Option[B]

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.

B

the result type of the binary operator.

op

the binary operator.

returns

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

Definition Classes
IterableOnceOps

def reduceOption[B >: A](op: (B, B) => B): Option[B]

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.

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.

Definition Classes
IterableOnceOps

def reduceRight[B >: A](op: (A, B) => B): B

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.

B

the result type of the binary operator.

op

the binary operator.

returns

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

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

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

Definition Classes
IterableOnceOps
Exceptions thrown

UnsupportedOperationException if this collection is empty.

def reduceRightOption[B >: A](op: (A, B) => B): Option[B]

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.

B

the result type of the binary operator.

op

the binary operator.

returns

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

Definition Classes
IterableOnceOps

def reversed: Iterable[A]

Attributes
protected
Definition Classes
IterableOnceOps

def scan[B >: A](z: B)(op: (B, B) => B): CC[B]

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 iterable collection containing the prefix scan of the elements in this iterable collection

def scanLeft[B](z: B)(op: (B, A) => B): CC[B]

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.

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

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

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. 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)
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 size of this collection.

Note: will not terminate for infinite-sized collections.

returns

the number of elements in this collection.

Definition Classes
IterableOnceOps

def sizeCompare(that: Iterable[_]): Int

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

that

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

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.

def sizeCompare(otherSize: Int): Int

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

otherSize

the test value that gets compared with the size.

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

final def sizeIs: SizeCompareOps

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
Annotations
@inline()

def slice(from: Int, until: Int): C

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.

from

the lowest index to include from this iterable collection.

until

the lowest index to EXCLUDE from this iterable collection.

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.

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

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.)

size

the number of elements per group

step

the distance between the first elements of successive groups

returns

An iterator producing iterable collections 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.

size

the number of elements per group

returns

An iterator producing iterable collections 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 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.

p

the test predicate

returns

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

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterators that were returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterators as well.

def splitAt(n: Int): (C, C)

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.

n

the position at which to split.

returns

a pair of iterable collections consisting of the first n elements of this iterable collection, and the other elements.

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterators that were returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterators as well.

def stepper[S <: Stepper[_]](implicit shape: StepperShape[A, S]): S

Returns a 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 StepperShape parameter defines the resulting Stepper type according to the element type of this collection.

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

Note that this method is overridden in subclasses and the return type is refined to S with EfficientSplit, for example 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.

Definition Classes
IterableOnce

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

Sums up the elements of this collection.

B

the result type of the + operator.

num

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

returns

the sum of all elements of this collection with respect to the + operator in num.

Definition Classes
IterableOnceOps

def tail: C

def tails: Iterator[C]

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.

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)

def take(n: Int): C

Selects the first n elements.

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

n

the number of elements to take from this iterable collection.

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.

Definition Classes
IterableOpsIterableOnceOps
Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

def takeRight(n: Int): C

Selects the last n elements.

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

n

the number of elements to take from this iterable collection.

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.

def takeWhile(p: (A) => Boolean): C

Takes longest prefix of elements that satisfy a predicate.

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

p

The predicate used to test elements.

returns

the longest prefix of this iterable collection whose elements all satisfy the predicate p.

Definition Classes
IterableOpsIterableOnceOps

def tapEach[U](f: (A) => U): C

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.

U

the return type of f

f

a function to apply to each element in this iterable collection

returns

The same logical collection as this

Definition Classes
IterableOpsIterableOnceOps

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. Example uses:

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

Definition Classes
IterableOnceOps

def toArray[B >: A](implicit arg0: ClassTag[B]): Array[B]

Convert collection to array.

Definition Classes
IterableOnceOps

final def toBuffer[B >: A]: Buffer[B]

Definition Classes
IterableOnceOps
Annotations
@inline()

def toIndexedSeq: immutable.IndexedSeq[A]

Definition Classes
IterableOnceOps

def toList: immutable.List[A]

Definition Classes
IterableOnceOps

def toMap[K, V](implicit ev: <:<[A, (K, V)]): immutable.Map[K, V]

Definition Classes
IterableOnceOps

def toSeq: immutable.Seq[A]

returns

This collection as a Seq[A]. This is equivalent to to(Seq) but might be faster.

Definition Classes
IterableOnceOps

def toSet[B >: A]: immutable.Set[B]

Definition Classes
IterableOnceOps

def toString(): String

Returns a string representation of the object.

The default representation is platform dependent.

returns

a string representation of the object.

Definition Classes
Any

def toVector: immutable.Vector[A]

Definition Classes
IterableOnceOps

def transpose[B](implicit asIterable: (A) => Iterable[B]): CC[CC[B]]

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.

B

the type of the elements of each iterable collection.

asIterable

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

returns

a two-dimensional iterable collection of iterable collections which has as nth row the nth column of this iterable collection.

Exceptions thrown

IllegalArgumentException if all collections in this iterable collection are not of the same size.

def unzip[A1, A2](implicit asPair: (A) => (A1, A2)): (CC[A1], CC[A2])

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))
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 iterable collection is a pair.

returns

a pair of iterable collections, containing the first, respectively second half of each element pair of this iterable collection.

def unzip3[A1, A2, A3](implicit asTriple: (A) => (A1, A2, A3)): (CC[A1], CC[A2], CC[A3])

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))
A1

the type of the first member of the element triples

A2

the type of the second member of the element triples

A3

the type of the third member of the element triples

asTriple

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

returns

a triple of iterable collections, containing the first, second, respectively third member of each element triple of this iterable collection.

def view: View[A]

def withFilter(p: (A) => Boolean): WithFilter[A, CC]

Creates a non-strict filter of this iterable collection.

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

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

p

the predicate used to test elements.

returns

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

def zip[B](that: IterableOnce[B]): CC[(A, B)]

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.

B

the type of the second half of the returned pairs

that

The iterable providing the second half of each result pair

returns

a new 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.

def zipAll[A1 >: A, B](that: Iterable[B], thisElem: A1, thatElem: B): CC[(A1, B)]

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.

that

the iterable providing the second half of each result pair

thisElem

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

thatElem

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

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.

def zipWithIndex: CC[(A, Int)]

Zips this iterable collection with its indices.

returns

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

Definition Classes
IterableOpsIterableOnceOps
Example:

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

Note

Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.

© 2002-2019 EPFL, with contributions from Lightbend.
Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.13.0/scala/collection/IterableOps.html