Iterator

scala.collection.Iterator

See theIterator companion object

trait Iterator[+A] extends IterableOnce[A], IterableOnceOps[A, Iterator, Iterator[A]]

Iterators are data structures that allow to iterate over a sequence of elements. They have a hasNext method for checking if there is a next element available, and a next method which returns the next element and advances the iterator.

An iterator is mutable: most operations on it change its state. While it is often used to iterate through the elements of a collection, it can also be used without being backed by any collection (see constructors on the companion object).

It is of particular importance to note that, unless stated otherwise, one should never use an iterator after calling a method on it. The two most important exceptions are also the sole abstract methods: next and hasNext.

Both these methods can be called any number of times without having to discard the iterator. Note that even hasNext may cause mutation -- such as when iterating from an input stream, where it will block until the stream is closed or some input becomes available.

Consider this example for safe and unsafe use:

def f[A](it: Iterator[A]) = {
 if (it.hasNext) {            // Safe to reuse "it" after "hasNext"
   it.next()                  // Safe to reuse "it" after "next"
   val remainder = it.drop(2) // it is *not* safe to use "it" again after this line!
   remainder.take(2)          // it is *not* safe to use "remainder" after this line!
 } else it
}

Attributes

Companion: object
Source: Iterator.scala
Graph
Supertypes: trait IterableOnceOps[A, Iterator, Iterator[A]]

trait IterableOnce[A]

class Object

trait Matchable

class Any
Known subtypes: class AbstractIterator[A]

class GroupedIterator[B]

class BufferedLineIterator

class LineIterator

class MatchIterator

trait BufferedIterator[A]

class Source

class BufferedSource
Show all
Self type: Iterator[A]

Members list

Type members

Classlikes

A flexible iterator for transforming an Iterator[A] into an Iterator[Seq[A]], with configurable sequence size, step, and strategy for dealing with remainder elements which don't fit evenly into the last group.

A GroupedIterator is yielded by grouped and by sliding, where the step may differ from the group size.

Attributes

Source: Iterator.scala
Supertypes: class AbstractIterator[Seq[B]]

trait Iterator[Seq[B]]

trait IterableOnceOps[Seq[B], Iterator, Iterator[Seq[B]]]

trait IterableOnce[Seq[B]]

class Object

trait Matchable

class Any
Show all

Value members

Abstract methods

Check if there is a next element available.

Attributes

Returns: true if there is a next element, false otherwise
Note: Reuse: The iterator remains valid for further use whatever result is returned.
Source: Iterator.scala

Return the next element and advance the iterator.

Attributes

Returns: the next element.
Throws: NoSuchElementException if there is no next element.
Note: Reuse: Advances the iterator, which may exhaust the elements. It is valid to make additional calls on the iterator.
Source: Iterator.scala

Concrete methods

Attributes

Source: Iterator.scala

Creates a buffered iterator from this iterator.

Attributes

Returns: a buffered iterator producing the same values as this iterator.
See also: scala.collection.BufferedIterator
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.
Source: Iterator.scala

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

Type parameters

B: the element type of the returned iterator.

Value parameters

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

Attributes

Returns: a new iterator 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.
Source: Iterator.scala

Attributes

Source: Iterator.scala

Tests whether this iterator contains a given value as an element.

Note: may not terminate for infinite iterators.

Value parameters

elem: the element to test.

Attributes

Returns: true if this iterator produces some value that is is equal (as determined by ==) to elem, false otherwise.
Note: Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Source: Iterator.scala

Builds a new iterator from this one without any duplicated elements on it.

Attributes

Returns: iterator with distinct elements
Note: Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Source: Iterator.scala

Builds a new iterator from this one without any duplicated elements as determined by == after applying the transforming function f.

Type parameters

B: the type of the elements after being transformed by f

Value parameters

f: The transforming function whose result is used to determine the uniqueness of each element

Attributes

Returns: iterator with distinct elements
Note: Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Source: Iterator.scala

Selects all elements except first n ones.

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

Value parameters

n: the number of elements to drop from this iterator.

Attributes

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

Drops longest prefix of elements that satisfy a predicate.

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

Value parameters

p: The predicate used to test elements.

Attributes

Returns: the longest suffix of this iterator whose first element does not satisfy the predicate p.
Source: Iterator.scala

Creates two new iterators that both iterate over the same elements as this iterator (in the same order).

Creates two new iterators that both iterate over the same elements as this iterator (in the same order). The duplicate iterators are considered equal if they are positioned at the same element.

Given that most methods on iterators will make the original iterator unfit for further use, this methods provides a reliable way of calling multiple such methods on an iterator.

Attributes

Returns: a pair of iterators
Note: The implementation may allocate temporary storage for elements iterated by one iterator but not yet by the other.

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.
Source: Iterator.scala

Selects all elements of this iterator which satisfy a predicate.

Value parameters

p: the predicate used to test elements.

Attributes

Returns: a new iterator consisting of all elements of this iterator that satisfy the given predicate p. The order of the elements is preserved.
Source: Iterator.scala

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

Value parameters

pred: the predicate used to test elements.

Attributes

Returns: a new iterator consisting of all elements of this iterator that do not satisfy the given predicate pred. Their order may not be preserved.
Source: Iterator.scala

Builds a new iterator by applying a function to all elements of this iterator 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 iterator. This might cause unexpected results sometimes. For example:

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

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

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

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

Type parameters

B: the element type of the returned collection.

Value parameters

f: the function to apply to each element.

Attributes

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

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

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

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

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

Type parameters

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

Value parameters

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

Attributes

Returns: a new iterator resulting from concatenating all element iterators.
Source: Iterator.scala

Returns an iterator which groups this iterator into fixed size blocks.

Returns an iterator which groups this iterator into fixed size blocks. Example usages:

// Returns List(List(1, 2, 3), List(4, 5, 6), List(7)))
(1 to 7).iterator.grouped(3).toList
// Returns List(List(1, 2, 3), List(4, 5, 6))
(1 to 7).iterator.grouped(3).withPartial(false).toList
// Returns List(List(1, 2, 3), List(4, 5, 6), List(7, 20, 25)
// Illustrating that withPadding's argument is by-name.
val it2 = Iterator.iterate(20)(_ + 5)
(1 to 7).iterator.grouped(3).withPadding(it2.next).toList

Attributes

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.
Source: Iterator.scala

Returns the index of the first occurrence of the specified object in this iterable object.

Note: may not terminate for infinite iterators.

Value parameters

elem: element to search for.

Attributes

Returns: the index of the first occurrence of elem in the values produced by this iterator, or -1 if such an element does not exist until the end of the iterator is reached.
Note: Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Source: Iterator.scala

Returns the index of the first occurrence of the specified object in this iterable object after or at some start index.

Note: may not terminate for infinite iterators.

Value parameters

elem: element to search for.
from: the start index

Attributes

Returns: the index >= from of the first occurrence of elem in the values produced by this iterator, or -1 if such an element does not exist until the end of the iterator is reached.
Note: Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change.
Source: Iterator.scala

Attributes

Source: Iterator.scala

Tests whether the iterator is empty.

Note: The default implementation creates and discards an iterator.

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

Attributes

Returns: true if the iterator contains no elements, false otherwise.
Definition Classes: IterableOnceOps
Source: Iterator.scala

Iterator can be used only once

Attributes

Source: Iterator.scala

Attributes

Source: Iterator.scala

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

Type parameters

B: the element type of the returned iterator.

Value parameters

f: the function to apply to each element.

Attributes

Returns: a new iterator resulting from applying the given function f to each element of this iterator and collecting the results.
Source: Iterator.scala

Wraps the value of next() in an option.

Attributes

Returns: Some(next) if a next element exists, None otherwise.
Source: Iterator.scala

A copy of this iterator with an element value appended until a given target length is reached.

Type parameters

B: the element type of the returned iterator.

Value parameters

elem: the padding value
len: the target length

Attributes

Returns: a new iterator consisting of all elements of this iterator followed by the minimal number of occurrences of elem so that the resulting collection has a length of at least len.
Source: Iterator.scala

Partitions this iterator in two iterators according to a predicate.

Value parameters

p: the predicate on which to partition

Attributes

Returns: a pair of iterators: the iterator that satisfies the predicate p and the iterator that does not. The relative order of the elements in the resulting iterators is the same as in the original iterator.
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.
Source: Iterator.scala

Returns this iterator with patched values.

Returns this iterator with patched values. Patching at negative indices is the same as patching starting at 0. Patching at indices at or larger than the length of the original iterator appends the patch to the end. If more values are replaced than actually exist, the excess is ignored.

Value parameters

from: The start index from which to patch
patchElems: The iterator of patch values
replaced: The number of values in the original iterator that are replaced by the patch.

Attributes

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

Checks whether corresponding elements of the given iterable collection compare equal (with respect to ==) to elements of this iterator.

Type parameters

B: the type of the elements of collection that.

Value parameters

that: the collection to compare

Attributes

Returns: true if both collections contain equal elements in the same order, false otherwise. <invalid inheritdoc annotation>
Source: Iterator.scala

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the type of the elements in the resulting collection

Value parameters

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

Attributes

Returns: collection with intermediate results
Source: Iterator.scala

Selects an interval of elements.

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

from <= indexOf(x) < until

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

Value parameters

from: the lowest index to include from this iterator.
until: the lowest index to EXCLUDE from this iterator.

Attributes

Returns: a iterator containing the elements greater than or equal to index from extending up to (but not including) index until of this iterator.
Source: Iterator.scala

Returns an iterator which presents a "sliding window" view of this iterator.

Returns an iterator which presents a "sliding window" view of this iterator. The first argument is the window size, and the second argument step is how far to advance the window on each iteration. The step defaults to 1.

The returned GroupedIterator can be configured to either pad a partial result to size size or suppress the partial result entirely.

Example usages:

// Returns List(ArraySeq(1, 2, 3), ArraySeq(2, 3, 4), ArraySeq(3, 4, 5))
(1 to 5).iterator.sliding(3).toList
// Returns List(ArraySeq(1, 2, 3, 4), ArraySeq(4, 5))
(1 to 5).iterator.sliding(4, 3).toList
// Returns List(ArraySeq(1, 2, 3, 4))
(1 to 5).iterator.sliding(4, 3).withPartial(false).toList
// Returns List(ArraySeq(1, 2, 3, 4), ArraySeq(4, 5, 20, 25))
// Illustrating that withPadding's argument is by-name.
val it2 = Iterator.iterate(20)(_ + 5)
(1 to 5).iterator.sliding(4, 3).withPadding(it2.next).toList

Value parameters

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

Attributes

Returns: A GroupedIterator producing Seq[B]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. This behavior can be configured.
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.
Source: Iterator.scala

Splits this iterator 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.

Attributes

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.
Source: Iterator.scala

Selects the first n elements.

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

Value parameters

n: the number of elements to take from this iterator.

Attributes

Returns: a iterator consisting only of the first n elements of this iterator, or else the whole iterator, if it has less than n elements. If n is negative, returns an empty iterator.
Source: Iterator.scala

Takes longest prefix of elements that satisfy a predicate.

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

Value parameters

p: The predicate used to test elements.

Attributes

Returns: the longest prefix of this iterator whose elements all satisfy the predicate p.
Source: Iterator.scala

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

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

Type parameters

U: the return type of f

Value parameters

f: a function to apply to each element in this iterator

Attributes

Returns: The same logical collection as this
Definition Classes: IterableOnceOps
Source: Iterator.scala

Converts this iterator to a string.

Attributes

Returns: "<iterator>"
Note: Reuse: The iterator remains valid for further use whatever result is returned.
Definition Classes: Any
Source: Iterator.scala

Creates an iterator over all the elements of this iterator that satisfy the predicate p.

Creates an iterator over all the elements of this iterator that satisfy the predicate p. The order of the elements is preserved.

Note: withFilter is the same as filter on iterators. It exists so that for-expressions with filters work over iterators.

Value parameters

p: the predicate used to test values.

Attributes

Returns: an iterator which produces those values of this iterator which satisfy the predicate p.
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.
Source: Iterator.scala

Attributes

Source: Iterator.scala

Attributes

Source: Iterator.scala

Zips this iterator with its indices.

Attributes

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

Deprecated methods

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

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

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

Attributes

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

Attributes

Deprecated: true
Source: Iterator.scala

Attributes

Deprecated: true
Source: Iterator.scala

Inherited methods

Appends all elements of this collection to a string builder.

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

Example:

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

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

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

Value parameters

b: the string builder to which elements are appended.

Attributes

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

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

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

Example:

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

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

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

Value parameters

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

Attributes

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

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

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)

Value parameters

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

Attributes

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

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

Note: may not terminate for infinite-sized collections.

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

Value parameters

pf: the partial function

Attributes

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

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

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

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

Type parameters

B: the type of the elements of the array.

Value parameters

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

Attributes

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

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

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

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

Type parameters

B: the type of the elements of the array.

Value parameters

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

Attributes

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

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

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

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

Type parameters

B: the type of the elements of the array.

Value parameters

xs: the array to fill.

Attributes

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: the type of the elements of that

Value parameters

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

Attributes

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

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

Note: will not terminate for infinite-sized collections.

Value parameters

p: the predicate used to test elements.

Attributes

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

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

Note: may not terminate for infinite-sized collections.

Value parameters

p: the predicate used to test elements.

Attributes

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

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

Note: may not terminate for infinite-sized collections.

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

Value parameters

p: the predicate used to test elements.

Attributes

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

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

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

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

Value parameters

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

Attributes

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

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

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

Attributes

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

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

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

Attributes

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

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

Note: may not terminate for infinite-sized collections.

Value parameters

p: the predicate used to test elements.

Attributes

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

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

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Tests whether this collection can be repeatedly traversed.

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

Attributes

Returns: true if it is repeatedly traversable, false otherwise.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

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

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B: The type over which the ordering is defined.

Value parameters

ord: An ordering to be used for comparing elements.

Attributes

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: The result type of the function f.

Value parameters

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

Attributes

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: The result type of the function f.

Value parameters

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

Attributes

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

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B: The type over which the ordering is defined.

Value parameters

ord: An ordering to be used for comparing elements.

Attributes

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

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B: The type over which the ordering is defined.

Value parameters

ord: An ordering to be used for comparing elements.

Attributes

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: The result type of the function f.

Value parameters

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

Attributes

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

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

Note: will not terminate for infinite-sized collections.

Type parameters

B: The result type of the function f.

Value parameters

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

Attributes

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

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type parameters

B: The type over which the ordering is defined.

Value parameters

ord: An ordering to be used for comparing elements.

Attributes

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

Displays all elements of this collection in a string.

Delegates to addString, which can be overridden.

Attributes

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

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

Delegates to addString, which can be overridden.

Value parameters

sep: the separator string.

Attributes

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

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

Delegates to addString, which can be overridden.

Value parameters

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

Attributes

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

Tests whether the collection is not empty.

Attributes

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

Multiplies together the elements of this collection.

The default implementation uses reduce for a known non-empty collection, foldLeft otherwise.

Note: will not terminate for infinite-sized collections.

Type parameters

B: the result type of the * operator.

Value parameters

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

Attributes

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

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

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

Type parameters

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

Value parameters

op: A binary operator that must be associative.

Attributes

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

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.

Attributes

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

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.

Attributes

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

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

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

Type parameters

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

Value parameters

op: A binary operator that must be associative.

Attributes

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

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.

Attributes

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

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

Note: will not terminate for infinite-sized collections.

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

Type parameters

B: the result type of the binary operator.

Value parameters

op: the binary operator.

Attributes

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

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

The size of this collection.

Note: will not terminate for infinite-sized collections.

Attributes

Returns: the number of elements in this collection.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

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

Value parameters

n: the position at which to split.

Attributes

Returns: a pair of collections consisting of the first n elements of this collection, and the other elements.
Inherited from:: IterableOnceOps
Source: IterableOnce.scala

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

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

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

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

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

Attributes

Inherited from:: IterableOnce
Source: IterableOnce.scala

Sums the elements of this collection.

The default implementation uses reduce for a known non-empty collection, foldLeft otherwise.

Note: will not terminate for infinite-sized collections.

Type parameters

B: the result type of the + operator.

Value parameters

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

Attributes

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

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

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

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

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Convert collection to array.

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

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

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

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Attributes

Inherited from:: IterableOnceOps
Source: IterableOnce.scala

Deprecated and Inherited methods

Attributes

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

Attributes

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

Attributes

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

Attributes

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

Attributes

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

Attributes

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

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