Empty

@SerialVersionUID(3L) case object Empty extends AbstractView[Nothing]

The empty view

The empty view

trait Singleton
trait Product
trait Mirror
trait Product
trait Equals
class AbstractView[Nothing]
trait View[Nothing]
class AbstractIterable[Nothing]
trait Iterable[Nothing]
trait IterableFactoryDefaults[Nothing, [A] =>> View[A]]
trait IterableOps[Nothing, [A] =>> View[A], View[Nothing]]
trait IterableOnceOps[Nothing, [A] =>> View[A], View[Nothing]]
trait IterableOnce[Nothing]
class Object
trait Matchable
class Any

Type members

Inherited types

The name of the type

The name of the type

Inherited from
Mirror
Inherited from
Singleton
Inherited from
Singleton

Value members

Concrete methods

override def isEmpty: Boolean
Definition Classes
def iterator: Iterator[Nothing]
override def knownSize: Int
Definition Classes

Inherited methods

final def ++[B](suffix: IterableOnce[B]): View[B]

Alias for concat

Alias for concat

Inherited from
IterableOps

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 Params
b

the string builder to which elements are appended.

Returns

the string builder b to which elements were appended.

Inherited from
IterableOnceOps

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 Params
b

the string builder to which elements are appended.

sep

the separator string.

Returns

the string builder b to which elements were appended.

Inherited from
IterableOnceOps

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 Params
b

the string builder to which elements are appended.

end

the ending string.

sep

the separator string.

start

the starting string.

Returns

the string builder b to which elements were appended.

Inherited from
IterableOnceOps
def collect[B](pf: PartialFunction[Nothing, B]): View[B]
Inherited from
IterableOps
def collectFirst[B](pf: PartialFunction[Nothing, 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.

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 Params
pf

the partial function

Returns

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

Example

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

Inherited from
IterableOnceOps
def concat[B](suffix: IterableOnce[B]): View[B]

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

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

Type Params
B

the element type of the returned collection.

Value Params
suffix

the traversable to append.

Returns

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

Inherited from
IterableOps
def copyToArray[B](xs: Array[B], start: Int, len: Int): Int

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

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 Params
B

the type of the elements of the array.

Value Params
len

the maximal number of elements to copy.

start

the starting index of xs.

xs

the array to fill.

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
@deprecatedOverriding("This should always forward to the 3-arg version of this method", since = "2.13.4")
def copyToArray[B](xs: Array[B], start: Int): Int

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

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 Params
B

the type of the elements of the array.

Value Params
start

the starting index of xs.

xs

the array to fill.

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
@deprecatedOverriding("This should always forward to the 3-arg version of this method", since = "2.13.4")
def copyToArray[B](xs: Array[B]): Int

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

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 Params
B

the type of the elements of the array.

Value Params
xs

the array to fill.

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
def corresponds[B](that: IterableOnce[B])(p: (Nothing, 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.

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 Params
B

the type of the elements of that

Value Params
p

the test predicate, which relates elements from both collections

that

the other collection

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
def count(p: Nothing => Boolean): Int

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

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

Note: will not terminate for infinite-sized collections.

Value Params
p

the predicate used to test elements.

Returns

the number of elements satisfying the predicate p.

Inherited from
IterableOnceOps
def drop(n: Int): View[Nothing]
Inherited from
IterableOps
def dropRight(n: Int): View[Nothing]

Selects all elements except last n ones.

Selects all elements except last n ones.

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

Value Params
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.

Inherited from
IterableOps
def dropWhile(p: Nothing => Boolean): View[Nothing]
Inherited from
IterableOps
override def empty: View[Nothing]
Definition Classes
Inherited from
View
def exists(p: Nothing => Boolean): Boolean

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

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

Note: may not terminate for infinite-sized collections.

Value Params
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

Inherited from
IterableOnceOps
def filter(pred: Nothing => Boolean): View[Nothing]
Inherited from
IterableOps
def filterNot(pred: Nothing => Boolean): View[Nothing]
Inherited from
IterableOps
def find(p: Nothing => Boolean): Option[Nothing]

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

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 Params
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.

Inherited from
IterableOnceOps
def flatMap[B](f: Nothing => IterableOnce[B]): View[B]
Inherited from
IterableOps
def flatten[B](asIterable: Nothing => IterableOnce[B]): View[B]
Inherited from
IterableOps
def fold[A1](z: A1)(op: (A1, A1) => A1): A1

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 Params
A1

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

Value Params
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).

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
def foldLeft[B](z: B)(op: (B, Nothing) => B): B

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

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 Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

z

the start value.

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
def foldRight[B](z: B)(op: (Nothing, B) => B): B

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

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 Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

z

the start value.

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
def forall(p: Nothing => Boolean): Boolean

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

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

Note: may not terminate for infinite-sized collections.

Value Params
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.

Inherited from
IterableOnceOps
def foreach[U](f: Nothing => U): Unit

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

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

Inherited from
IterableOnceOps
protected def fromSpecific(coll: IterableOnce[Nothing]): View[Nothing]
def groupBy[K](f: Nothing => K): Map[K, View[Nothing]]

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

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

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

Type Params
K

the type of keys returned by the discriminator function.

Value Params
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.

Inherited from
IterableOps
def groupMap[K, B](key: Nothing => K)(f: Nothing => B): Map[K, View[B]]

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

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

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

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

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

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

Type Params
B

the type of values returned by the transformation function

K

the type of keys returned by the discriminator function

Value Params
f

the element transformation function

key

the discriminator function

Inherited from
IterableOps
def groupMapReduce[K, B](key: Nothing => K)(f: Nothing => B)(reduce: (B, B) => B): Map[K, B]

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

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

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

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

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

Inherited from
IterableOps
def grouped(size: Int): Iterator[View[Nothing]]

Partitions elements in fixed size iterable collections.

Partitions elements in fixed size iterable collections.

Value Params
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
Inherited from
IterableOps
def head: Nothing

Selects the first element of this iterable collection.

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.

Throws
NoSuchElementException

if the iterable collection is empty.

Inherited from
IterableOps
def headOption: Option[Nothing]

Optionally selects the first element.

Optionally selects the first element.

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

Returns

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

Inherited from
IterableOps
def init: View[Nothing]

The initial part of the collection without its last element.

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.

Inherited from
IterableOps
def inits: Iterator[View[Nothing]]

Iterates over the inits of this iterable collection.

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

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

Returns

an iterator over all the inits of this iterable collection

Example

List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)

Inherited from
IterableOps
Definition Classes
Inherited from
IterableOps
override def iterableFactory: IterableFactory[[A] =>> View[A]]
Definition Classes
Inherited from
View
def last: Nothing

Selects the last element.

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.

Throws
NoSuchElementException

If the iterable collection is empty.

Inherited from
IterableOps
def lastOption: Option[Nothing]

Optionally selects the last element.

Optionally selects the last element.

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

Returns

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

Inherited from
IterableOps
def lazyZip[B](that: Iterable[B]): LazyZip2[Nothing, B, Empty]

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

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

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

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

the type of the second element in each eventual pair

Value Params
that

the iterable providing the second element of each eventual pair

Returns

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

Inherited from
Iterable
def map[B](f: Nothing => B): View[B]
Inherited from
IterableOps
def max[B](ord: Ordering[B]): Nothing

Finds the largest element.

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type Params
B

The type over which the ordering is defined.

Value Params
ord

An ordering to be used for comparing elements.

Returns

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

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def maxBy[B](f: Nothing => B)(cmp: Ordering[B]): Nothing

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

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

Note: will not terminate for infinite-sized collections.

Type Params
B

The result type of the function f.

Value Params
cmp

An ordering to be used for comparing elements.

f

The measuring function.

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
def maxByOption[B](f: Nothing => B)(cmp: Ordering[B]): Option[Nothing]

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

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

Note: will not terminate for infinite-sized collections.

Type Params
B

The result type of the function f.

Value Params
cmp

An ordering to be used for comparing elements.

f

The measuring function.

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
def maxOption[B](ord: Ordering[B]): Option[Nothing]

Finds the largest element.

Finds the largest element.

Note: will not terminate for infinite-sized collections.

Type Params
B

The type over which the ordering is defined.

Value Params
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.

Inherited from
IterableOnceOps
def min[B](ord: Ordering[B]): Nothing

Finds the smallest element.

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type Params
B

The type over which the ordering is defined.

Value Params
ord

An ordering to be used for comparing elements.

Returns

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

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def minBy[B](f: Nothing => B)(cmp: Ordering[B]): Nothing

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

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

Note: will not terminate for infinite-sized collections.

Type Params
B

The result type of the function f.

Value Params
cmp

An ordering to be used for comparing elements.

f

The measuring function.

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
def minByOption[B](f: Nothing => B)(cmp: Ordering[B]): Option[Nothing]

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

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

Note: will not terminate for infinite-sized collections.

Type Params
B

The result type of the function f.

Value Params
cmp

An ordering to be used for comparing elements.

f

The measuring function.

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
def minOption[B](ord: Ordering[B]): Option[Nothing]

Finds the smallest element.

Finds the smallest element.

Note: will not terminate for infinite-sized collections.

Type Params
B

The type over which the ordering is defined.

Value Params
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.

Inherited from
IterableOnceOps
final def mkString: String

Displays all elements of this collection in a 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.

Inherited from
IterableOnceOps
final def mkString(sep: String): String

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

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

Delegates to addString, which can be overridden.

Value Params
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.

Example

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

Inherited from
IterableOnceOps
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.

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

Delegates to addString, which can be overridden.

Value Params
end

the ending string.

sep

the separator string.

start

the starting 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.

Example

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

Inherited from
IterableOnceOps
protected def newSpecificBuilder: Builder[Nothing, View[Nothing]]
@deprecatedOverriding("nonEmpty is defined as !isEmpty; override isEmpty instead", "2.13.0")

Tests whether the collection is not empty.

Tests whether the collection is not empty.

Returns

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

Inherited from
IterableOnceOps
def partition(p: Nothing => Boolean): (View[Nothing], View[Nothing])

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

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

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

Inherited from
IterableOps
def partitionMap[A1, A2](f: Nothing => Either[A1, A2]): (View[A1], View[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.

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

Example:

val xs = Iterable(1, "one", 2, "two", 3, "three") partitionMap {
 case i: Int => Left(i)
 case s: String => Right(s)
}
// xs == (Iterable(1, 2, 3),
//        Iterable(one, two, three))
Type Params
A1

the element type of the first resulting collection

A2

the element type of the second resulting collection

Value Params
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.

Inherited from
IterableOps
def product[B](num: Numeric[B]): B

Multiplies up the elements of this collection.

Multiplies up the elements of this collection.

Note: will not terminate for infinite-sized collections.

Type Params
B

the result type of the * operator.

Value Params
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.

Inherited from
IterableOnceOps

An iterator over the names of all the elements of this product.

An iterator over the names of all the elements of this product.

Inherited from
Product

An iterator over all the elements of this product.

An iterator over all the elements of this product.

Returns

in the default implementation, an Iterator[Any]

Inherited from
Product
def reduce[B](op: (B, B) => B): B

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

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 Params
B

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

Value Params
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.

Throws
UnsupportedOperationException

if this collection is empty.

Inherited from
IterableOnceOps
def reduceLeft[B](op: (B, Nothing) => B): B

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

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 Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

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
def reduceLeftOption[B](op: (B, Nothing) => B): Option[B]

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

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 Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

Returns

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

Inherited from
IterableOnceOps
def reduceOption[B](op: (B, B) => B): Option[B]

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

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 Params
B

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

Value Params
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.

Inherited from
IterableOnceOps
def reduceRight[B](op: (Nothing, B) => B): B

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

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 Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

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
def reduceRightOption[B](op: (Nothing, B) => B): Option[B]

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

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 Params
B

the result type of the binary operator.

Value Params
op

the binary operator.

Returns

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

Inherited from
IterableOnceOps
protected def reversed: Iterable[Nothing]
Inherited from
IterableOnceOps
def scan[B](z: B)(op: (B, B) => B): View[B]

Computes a prefix scan of the elements of the collection.

Computes a prefix scan of the elements of the collection.

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

Type Params
B

element type of the resulting collection

Value Params
op

the associative operator for the scan

z

neutral element for the operator op

Returns

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

Inherited from
IterableOps
def scanLeft[B](z: B)(op: (B, Nothing) => B): View[B]
Inherited from
IterableOps
def scanRight[B](z: B)(op: (Nothing, B) => B): View[B]

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

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

Note: will not terminate for infinite-sized collections.

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

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

Example:

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

the type of the elements in the resulting collection

Value Params
op

the binary operator applied to the intermediate result and the element

z

the initial value

Returns

collection with intermediate results

Inherited from
IterableOps
def size: Int

The size of this collection.

The size of this collection.

Note: will not terminate for infinite-sized collections.

Returns

the number of elements in this collection.

Inherited from
IterableOnceOps
def sizeCompare(that: Iterable[_]): Int

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

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

Value Params
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.

Inherited from
IterableOps
def sizeCompare(otherSize: Int): Int

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

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

Value Params
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
Inherited from
IterableOps

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

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
Inherited from
IterableOps
def slice(from: Int, until: Int): View[Nothing]
Inherited from
IterableOps
def sliding(size: Int, step: Int): Iterator[View[Nothing]]

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

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

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

Value Params
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 smaller if there are fewer than size elements remaining to be grouped.

See also
Example

List(1, 2, 3, 4, 5).sliding(2, 2) = Iterator(List(1, 2), List(3, 4), List(5))

List(1, 2, 3, 4, 5, 6).sliding(2, 3) = Iterator(List(1, 2), List(4, 5))

Inherited from
IterableOps
def sliding(size: Int): Iterator[View[Nothing]]

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

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

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

Value Params
size

the number of elements per group

Returns

An iterator producing iterable collections of size size, except for a non-empty collection with less than size elements, which returns an iterator that produces the source collection itself as its only element.

See also
Example

List().sliding(2) = empty iterator

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

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

List(1, 2, 3).sliding(2) = Iterator(List(1, 2), List(2, 3))

Inherited from
IterableOps
def span(p: Nothing => Boolean): (View[Nothing], View[Nothing])
Inherited from
IterableOps
override def splitAt(n: Int): (View[Nothing], View[Nothing])
Definition Classes
Inherited from
IterableOps
def stepper[S <: Stepper[_]](shape: StepperShape[Nothing, S]): S

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

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.

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.

Inherited from
IterableOnce
def sum[B](num: Numeric[B]): B

Sums up the elements of this collection.

Sums up the elements of this collection.

Note: will not terminate for infinite-sized collections.

Type Params
B

the result type of the + operator.

Value Params
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.

Inherited from
IterableOnceOps
def tail: View[Nothing]

The rest of the collection without its first element.

The rest of the collection without its first element.

Inherited from
IterableOps
def tails: Iterator[View[Nothing]]

Iterates over the tails of this iterable collection.

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

Returns

an iterator over all the tails of this iterable collection

Example

List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)

Inherited from
IterableOps
def take(n: Int): View[Nothing]
Inherited from
IterableOps
def takeRight(n: Int): View[Nothing]

Selects the last n elements.

Selects the last n elements.

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

Value Params
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.

Inherited from
IterableOps
def takeWhile(p: Nothing => Boolean): View[Nothing]

Takes longest prefix of elements that satisfy a predicate.

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 Params
p

The predicate used to test elements.

Returns

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

Inherited from
IterableOps
override def tapEach[U](f: Nothing => U): View[Nothing]
Definition Classes
Inherited from
IterableOps
def to[C1](factory: Factory[Nothing, C1]): C1

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

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

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

Inherited from
IterableOnceOps
def toArray[B](`evidence$1`: ClassTag[B]): Array[B]

Convert collection to array.

Convert collection to array.

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

Inherited from
IterableOnceOps
final def toBuffer[B]: Buffer[B]
Inherited from
IterableOnceOps
def toIndexedSeq: IndexedSeq[Nothing]
Inherited from
IterableOnceOps
final def toIterable: Empty
Inherited from
Iterable
def toList: List[Nothing]
Inherited from
IterableOnceOps
def toMap[K, V](ev: Nothing <:< (K, V)): Map[K, V]
Inherited from
IterableOnceOps
def toSeq: Seq[Nothing]
Returns

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

Inherited from
IterableOnceOps
def toSet[B]: Set[B]
Inherited from
IterableOnceOps
override def toString: String
Definition Classes
View -> Iterable -> Any
Inherited from
View
def toVector: Vector[Nothing]
Inherited from
IterableOnceOps
def transpose[B](asIterable: Nothing => Iterable[B]): View[View[B]]

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

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

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

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

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

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

Type Params
B

the type of the elements of each iterable collection.

Value Params
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.

Throws
IllegalArgumentException

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

Inherited from
IterableOps
def unzip[A1, A2](asPair: Nothing => (A1, A2)): (View[A1], View[A2])

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

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

val xs = Iterable(
           (1, "one"),
           (2, "two"),
           (3, "three")).unzip
// xs == (Iterable(1, 2, 3),
//        Iterable(one, two, three))
Type Params
A1

the type of the first half of the element pairs

A2

the type of the second half of the element pairs

Value Params
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.

Inherited from
IterableOps
def unzip3[A1, A2, A3](asTriple: Nothing => (A1, A2, A3)): (View[A1], View[A2], View[A3])

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

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

val xs = Iterable(
           (1, "one", '1'),
           (2, "two", '2'),
           (3, "three", '3')).unzip3
// xs == (Iterable(1, 2, 3),
//        Iterable(one, two, three),
//        Iterable(1, 2, 3))
Type Params
A1

the type of the first member of the element triples

A2

the type of the second member of the element triples

A3

the type of the third member of the element triples

Value Params
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.

Inherited from
IterableOps
override def view: View[Nothing]
Definition Classes
Inherited from
View
def withFilter(p: Nothing => Boolean): WithFilter[Nothing, [A] =>> View[A]]

Creates a non-strict filter of this iterable collection.

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.

Value Params
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.

Inherited from
IterableOps
def zip[B](that: IterableOnce[B]): View[(Nothing, B)]

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

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

Type Params
B

the type of the second half of the returned pairs

Value Params
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.

Inherited from
IterableOps
def zipAll[A1, B](that: Iterable[B], thisElem: A1, thatElem: B): View[(A1, B)]

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

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

Value Params
that

the iterable providing the second half of each result pair

thatElem

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

thisElem

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

Returns

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

Inherited from
IterableOps
def zipWithIndex: View[(Nothing, Int)]
Inherited from
IterableOps

Deprecated and Inherited methods

@deprecated("Use ++ instead of ++: for collections of type Iterable", "2.13.0")
def ++:[B](that: IterableOnce[B]): View[B]
Deprecated
Inherited from
IterableOps
@deprecated("Use foldLeft instead of /:", "2.13.0") @inline
final def /:[B](z: B)(op: (B, Nothing) => B): B
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use foldRight instead of :\\", "2.13.0") @inline
final def :\[B](z: B)(op: (Nothing, B) => B): B
Deprecated
Inherited from
IterableOnceOps
@deprecated("`aggregate` is not relevant for sequential collections. Use `foldLeft(z)(seqop)` instead.", "2.13.0")
def aggregate[B](z: => B)(seqop: (B, Nothing) => B, combop: (B, B) => B): B
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use iterableFactory instead", "2.13.0") @deprecatedOverriding("Use iterableFactory instead", "2.13.0") @inline
def companion: IterableFactory[[A] =>> View[A]]
Deprecated
Inherited from
IterableOps
@deprecated("Use `dest ++= coll` instead", "2.13.0") @inline
final def copyToBuffer[B](dest: Buffer[B]): Unit
Deprecated
Inherited from
IterableOnceOps
@deprecated("Views no longer know about their underlying collection type; .force always returns an IndexedSeq", "2.13.0") @inline
def force: IndexedSeq[Nothing]
Deprecated
Inherited from
View
@deprecated("Check .knownSize instead of .hasDefiniteSize for more actionable information (see scaladoc for details)", "2.13.0")

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

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

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

Returns

true if this collection is known to have finite size, false otherwise.

See also

method knownSize for a more useful alternative

Deprecated

This method is deprecated in 2.13 because it does not provide any actionable information. As noted above, even the collection library itself does not use it. When there is no guarantee that a collection is finite, it is generally best to attempt a computation anyway and document that it will not terminate for infinite collections rather than backing out because this would prevent performing the computation on collections that are in fact finite even though hasDefiniteSize returns false.

Inherited from
IterableOnceOps
@deprecated("Use coll instead of repr in a collection implementation, use the collection value itself from the outside", "2.13.0")
final def repr: View[Nothing]
Deprecated
Inherited from
IterableOps
@deprecated("Iterable.seq always returns the iterable itself", "2.13.0")
def seq: Empty
Deprecated
Inherited from
Iterable
@deprecated("Use .iterator instead of .toIterator", "2.13.0") @inline
final def toIterator: Iterator[Nothing]
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use .to(LazyList) instead of .toStream", "2.13.0") @inline
final def toStream: Stream[Nothing]
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use toIterable instead", "2.13.0")
final def toTraversable: Iterable[Nothing]

Converts this iterable collection to an unspecified Iterable.

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

Returns

An Iterable containing all elements of this iterable collection.

Deprecated
Inherited from
IterableOps
@deprecated("Use .view.slice(from, until) instead of .view(from, until)", "2.13.0")
def view(from: Int, until: Int): View[Nothing]

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

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

Deprecated
Inherited from
IterableOps