Option

@SerialVersionUID(-114498752079829388L) sealed abstract class Option[+A] extends IterableOnce[A] with Product with Serializable

Represents optional values. Instances of Option are either an instance of scala.Some or the object None.

The most idiomatic way to use an scala.Option instance is to treat it as a collection or monad and use map,flatMap, filter, or foreach:

val name: Option[String] = request getParameter "name"
val upper = name map { _.trim } filter { _.length != 0 } map { _.toUpperCase }
println(upper getOrElse "")

Note that this is equivalent to

val upper = for {
  name <- request getParameter "name"
  trimmed <- Some(name.trim)
  upper <- Some(trimmed.toUpperCase) if trimmed.length != 0
} yield upper
println(upper getOrElse "")

Because of how for comprehension works, if None is returned from request.getParameter, the entire expression results in None

This allows for sophisticated chaining of scala.Option values without having to check for the existence of a value.

These are useful methods that exist for both scala.Some and None. - isDefined — True if not empty - isEmpty — True if empty - nonEmpty — True if not empty - orElse — Evaluate and return alternate optional value if empty - getOrElse — Evaluate and return alternate value if empty - get — Return value, throw exception if empty - fold — Apply function on optional value, return default if empty - map — Apply a function on the optional value - flatMap — Same as map but function must return an optional value - foreach — Apply a procedure on option value - collect — Apply partial pattern match on optional value - filter — An optional value satisfies predicate - filterNot — An optional value doesn't satisfy predicate - exists — Apply predicate on optional value, or false if empty - forall — Apply predicate on optional value, or true if empty - contains — Checks if value equals optional value, or false if empty - zip — Combine two optional values to make a paired optional value - unzip — Split an optional pair to two optional values - unzip3 — Split an optional triple to three optional values - toList — Unary list of optional value, otherwise the empty list

A less-idiomatic way to use scala.Option values is via pattern matching:

val nameMaybe = request getParameter "name"
nameMaybe match {
  case Some(name) =>
    println(name.trim.toUppercase)
  case None =>
    println("No name value")
}

Interacting with code that can occasionally return null can be safely wrapped in scala.Option to become None and scala.Some otherwise.

val abc = new java.util.HashMap[Int, String]
abc.put(1, "A")
bMaybe = Option(abc.get(2))
bMaybe match {
 case Some(b) =>
   println(s"Found $b")
 case None =>
   println("Not found")
}
Note

Many of the methods in here are duplicative with those in the Traversable hierarchy, but they are duplicated for a reason: the implicit conversion tends to leave one with an Iterable in situations where one could have retained an Option.

Companion
object
trait Product
trait Equals
class Object
trait Matchable
class Any
object None
class Some[A]

Type members

Classlikes

class WithFilter(p: A => Boolean)

We need a whole WithFilter class to honor the "doesn't create a new collection" contract even though it seems unlikely to matter much in a collection with max size 1.

We need a whole WithFilter class to honor the "doesn't create a new collection" contract even though it seems unlikely to matter much in a collection with max size 1.

Value members

Abstract methods

def get: A

Returns the option's value.

Returns the option's value.

This is equivalent to:

option match {
 case Some(x) => x
 case None    => throw new Exception
}
Throws
NoSuchElementException

if the option is empty.

Note

The option must be nonempty.

Concrete methods

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

Returns a scala.Some containing the result of applying pf to this scala.Option's contained value, if this option is nonempty and pf is defined for that value.

Returns a scala.Some containing the result of applying pf to this scala.Option's contained value, if this option is nonempty and pf is defined for that value. Returns None otherwise.

Value Params
pf

the partial function.

Returns

the result of applying pf to this scala.Option's value (if possible), or None.

Example

// Returns Some(HTTP) because the partial function covers the case.
Some("http") collect {case "http" => "HTTP"}
// Returns None because the partial function doesn't cover the case.
Some("ftp") collect {case "http" => "HTTP"}
// Returns None because the option is empty. There is no value to pass to the partial function.
None collect {case value => value}
final def contains[A1 >: A](elem: A1): Boolean

Tests whether the option contains a given value as an element.

Tests whether the option contains a given value as an element.

This is equivalent to:

option match {
 case Some(x) => x == elem
 case None    => false
}
Value Params
elem

the element to test.

Returns

true if the option has an element that is equal (as determined by ==) to elem, false otherwise.

Example

// Returns true because Some instance contains string "something" which equals "something".
Some("something") contains "something"
// Returns false because "something" != "anything".
Some("something") contains "anything"
// Returns false when method called on None.
None contains "anything"
final def exists(p: A => Boolean): Boolean

Returns true if this option is nonempty and the predicate p returns true when applied to this scala.Option's value.

Returns true if this option is nonempty and the predicate p returns true when applied to this scala.Option's value. Otherwise, returns false.

This is equivalent to:

option match {
 case Some(x) => p(x)
 case None    => false
}
Value Params
p

the predicate to test

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

Returns this scala.Option if it is nonempty and applying the predicate p to this scala.Option's value returns true.

Returns this scala.Option if it is nonempty and applying the predicate p to this scala.Option's value returns true. Otherwise, return None.

This is equivalent to:

option match {
 case Some(x) if p(x) => Some(x)
 case _               => None
}
Value Params
p

the predicate used for testing.

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

Returns this scala.Option if it is nonempty and applying the predicate p to this scala.Option's value returns false.

Returns this scala.Option if it is nonempty and applying the predicate p to this scala.Option's value returns false. Otherwise, return None.

This is equivalent to:

option match {
 case Some(x) if !p(x) => Some(x)
 case _                => None
}
Value Params
p

the predicate used for testing.

final def flatMap[B](f: A => Option[B]): Option[B]

Returns the result of applying f to this scala.Option's value if this scala.Option is nonempty.

Returns the result of applying f to this scala.Option's value if this scala.Option is nonempty. Returns None if this scala.Option is empty. Slightly different from map in that f is expected to return an scala.Option (which could be None).

This is equivalent to:

option match {
 case Some(x) => f(x)
 case None    => None
}
Value Params
f

the function to apply

See also

map

foreach

def flatten[B](ev: A <:< Option[B]): Option[B]

Returns the nested scala.Option value if it is nonempty.

Returns the nested scala.Option value if it is nonempty. Otherwise, return None.

This is equivalent to:

option match {
 case Some(Some(b)) => Some(b)
 case _             => None
}
Value Params
ev

an implicit conversion that asserts that the value is also an scala.Option.

See also

flatMap

Example

Some(Some("something")).flatten
final def fold[B](ifEmpty: => B)(f: A => B): B

Returns the result of applying f to this scala.Option's value if the scala.Option is nonempty.

Returns the result of applying f to this scala.Option's value if the scala.Option is nonempty. Otherwise, evaluates expression ifEmpty.

This is equivalent to:

option match {
 case Some(x) => f(x)
 case None    => ifEmpty
}

This is also equivalent to:

option map f getOrElse ifEmpty
Value Params
f

the function to apply if nonempty.

ifEmpty

the expression to evaluate if empty.

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

Returns true if this option is empty or the predicate p returns true when applied to this scala.Option's value.

Returns true if this option is empty or the predicate p returns true when applied to this scala.Option's value.

This is equivalent to:

option match {
 case Some(x) => p(x)
 case None    => true
}
Value Params
p

the predicate to test

final def foreach[U](f: A => U): Unit

Apply the given procedure f to the option's value, if it is nonempty.

Apply the given procedure f to the option's value, if it is nonempty. Otherwise, do nothing.

This is equivalent to:

option match {
 case Some(x) => f(x)
 case None    => ()
}
Value Params
f

the procedure to apply.

See also

map

flatMap

final def getOrElse[B >: A](default: => B): B

Returns the option's value if the option is nonempty, otherwise return the result of evaluating default.

Returns the option's value if the option is nonempty, otherwise return the result of evaluating default.

This is equivalent to:

option match {
 case Some(x) => x
 case None    => default
}
Value Params
default

the default expression.

final def isDefined: Boolean

Returns true if the option is an instance of scala.Some, false otherwise.

Returns true if the option is an instance of scala.Some, false otherwise.

This is equivalent to:

option match {
 case Some(_) => true
 case None    => false
}
final def isEmpty: Boolean

Returns true if the option is None, false otherwise.

Returns true if the option is None, false otherwise.

This is equivalent to:

option match {
 case Some(_) => false
 case None    => true
}
Implicitly added by option2Iterable

Returns a singleton iterator returning the scala.Option's value if it is nonempty, or an empty iterator if the option is empty.

Returns a singleton iterator returning the scala.Option's value if it is nonempty, or an empty iterator if the option is empty.

final override def knownSize: Int
Definition Classes
def lazyZip[B](that: Iterable[B]): LazyZip2[A, B, Iterable[A]]
Implicitly added by option2Iterable

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.

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

Returns a scala.Some containing the result of applying f to this scala.Option's value if this scala.Option is nonempty.

Returns a scala.Some containing the result of applying f to this scala.Option's value if this scala.Option is nonempty. Otherwise return None.

This is equivalent to:

option match {
 case Some(x) => Some(f(x))
 case None    => None
}
Value Params
f

the function to apply

See also

flatMap

foreach

Note

This is similar to flatMap except here, f does not need to wrap its result in an scala.Option.

final def nonEmpty: Boolean

Returns false if the option is None, true otherwise.

Returns false if the option is None, true otherwise.

This is equivalent to:

option match {
 case Some(_) => true
 case None    => false
}
Note

Implemented here to avoid the implicit conversion to Iterable.

final def orElse[B >: A](alternative: => Option[B]): Option[B]

Returns this scala.Option if it is nonempty, otherwise return the result of evaluating alternative.

Returns this scala.Option if it is nonempty, otherwise return the result of evaluating alternative.

This is equivalent to:

option match {
 case Some(x) => Some(x)
 case None    => alternative
}
Value Params
alternative

the alternative expression.

final def orNull[A1 >: A](ev: Null <:< A1): A1

Returns the option's value if it is nonempty, or null if it is empty.

Returns the option's value if it is nonempty, or null if it is empty.

Although the use of null is discouraged, code written to use scala.Option must often interface with code that expects and returns nulls.

This is equivalent to:

option match {
 case Some(x) => x
 case None    => null
}
Example

val initialText: Option[String] = getInitialText
val textField = new JComponent(initialText.orNull,20)
final def toIterable: Iterable[A]
Implicitly added by option2Iterable
final def toLeft[X](right: => X): Either[A, X]

Returns a scala.util.Right containing the given argument right if this is empty, or a scala.util.Left containing this scala.Option's value if this scala.Option is nonempty.

Returns a scala.util.Right containing the given argument right if this is empty, or a scala.util.Left containing this scala.Option's value if this scala.Option is nonempty.

This is equivalent to:

option match {
 case Some(x) => Left(x)
 case None    => Right(right)
}
Value Params
right

the expression to evaluate and return if this is empty

See also

toRight

def toList: List[A]

Returns a singleton list containing the scala.Option's value if it is nonempty, or the empty list if the scala.Option is empty.

Returns a singleton list containing the scala.Option's value if it is nonempty, or the empty list if the scala.Option is empty.

This is equivalent to:

option match {
 case Some(x) => List(x)
 case None    => Nil
}
final def toRight[X](left: => X): Either[X, A]

Returns a scala.util.Left containing the given argument left if this scala.Option is empty, or a scala.util.Right containing this scala.Option's value if this is nonempty.

Returns a scala.util.Left containing the given argument left if this scala.Option is empty, or a scala.util.Right containing this scala.Option's value if this is nonempty.

This is equivalent to:

option match {
 case Some(x) => Right(x)
 case None    => Left(left)
}
Value Params
left

the expression to evaluate and return if this is empty

See also

toLeft

final def unzip[A1, A2](asPair: A <:< (A1, A2)): (Option[A1], Option[A2])

Converts an Option of a pair into an Option of the first element and an Option of the second element.

Converts an Option of a pair into an Option of the first element and an Option of the second element.

This is equivalent to:

option match {
  case Some((x, y)) => (Some(x), Some(y))
  case _            => (None,    None)
}
Type Params
A1

the type of the first half of the element pair

A2

the type of the second half of the element pair

Value Params
asPair

an implicit conversion which asserts that the element type of this Option is a pair.

Returns

a pair of Options, containing, respectively, the first and second half of the element pair of this Option.

final def unzip3[A1, A2, A3](asTriple: A <:< (A1, A2, A3)): (Option[A1], Option[A2], Option[A3])

Converts an Option of a triple into three Options, one containing the element from each position of the triple.

Converts an Option of a triple into three Options, one containing the element from each position of the triple.

This is equivalent to:

option match {
  case Some((x, y, z)) => (Some(x), Some(y), Some(z))
  case _               => (None,    None,    None)
}
Type Params
A1

the type of the first of three elements in the triple

A2

the type of the second of three elements in the triple

A3

the type of the third of three elements in the triple

Value Params
asTriple

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

Returns

a triple of Options, containing, respectively, the first, second, and third elements from the element triple of this Option.

final def withFilter(p: A => Boolean): WithFilter

Necessary to keep scala.Option from being implicitly converted to scala.collection.Iterable in for comprehensions.

Necessary to keep scala.Option from being implicitly converted to scala.collection.Iterable in for comprehensions.

final def zip[A1 >: A, B](that: Option[B]): Option[(A1, B)]

Returns a scala.Some formed from this option and another option by combining the corresponding elements in a pair.

Returns a scala.Some formed from this option and another option by combining the corresponding elements in a pair. If either of the two options is empty, None is returned.

This is equivalent to:

(option1, option2) match {
  case (Some(x), Some(y)) => Some((x, y))
  case _                  => None
}
Value Params
that

the options which is going to be zipped

Example

// Returns Some(("foo", "bar")) because both options are nonempty.
Some("foo") zip Some("bar")
// Returns None because `that` option is empty.
Some("foo") zip None
// Returns None because `this` option is empty.
None zip Some("bar")

Deprecated methods

@deprecated("Iterable.seq always returns the iterable itself", "2.13.0")
def seq: Iterable[A]
Implicitly added by option2Iterable
Deprecated

Inherited methods

final def ++[B >: A](suffix: IterableOnce[B]): Iterable[B]
Implicitly added by option2Iterable

Alias for concat

Alias for concat

Inherited from
IterableOps
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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 canEqual(that: Any): Boolean

A method that should be called from every well-designed equals method that is open to be overridden in a subclass.

A method that should be called from every well-designed equals method that is open to be overridden in a subclass. See Programming in Scala, Chapter 28 for discussion and design.

Value Params
that

the value being probed for possible equality

Returns

true if this instance can possibly equal that, otherwise false

Inherited from
Equals
def collect[B](pf: PartialFunction[A, B]): Iterable[B]
Implicitly added by option2Iterable
Inherited from
IterableOps
def collectFirst[B](pf: PartialFunction[A, B]): Option[B]
Implicitly added by option2Iterable

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 >: A](suffix: IterableOnce[B]): Iterable[B]
Implicitly added by option2Iterable

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 >: A](xs: Array[B], start: Int, len: Int): Int
Implicitly added by option2Iterable

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 >: A](xs: Array[B], start: Int): Int
Implicitly added by option2Iterable

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 >: A](xs: Array[B]): Int
Implicitly added by option2Iterable

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: (A, B) => Boolean): Boolean
Implicitly added by option2Iterable

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: A => Boolean): Int
Implicitly added by option2Iterable

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): Iterable[A]
Implicitly added by option2Iterable
Inherited from
IterableOps
def dropRight(n: Int): Iterable[A]
Implicitly added by option2Iterable

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: A => Boolean): Iterable[A]
Implicitly added by option2Iterable
Inherited from
IterableOps
def exists(p: A => Boolean): Boolean
Implicitly added by option2Iterable

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: A => Boolean): Iterable[A]
Implicitly added by option2Iterable
Inherited from
IterableOps
def filterNot(pred: A => Boolean): Iterable[A]
Implicitly added by option2Iterable
Inherited from
IterableOps
def find(p: A => Boolean): Option[A]
Implicitly added by option2Iterable

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: A => IterableOnce[B]): Iterable[B]
Implicitly added by option2Iterable
Inherited from
IterableOps
def flatten[B](asIterable: A => IterableOnce[B]): Iterable[B]
Implicitly added by option2Iterable
Inherited from
IterableOps
def fold[A1 >: A](z: A1)(op: (A1, A1) => A1): A1
Implicitly added by option2Iterable

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, A) => B): B
Implicitly added by option2Iterable

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: (A, B) => B): B
Implicitly added by option2Iterable

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: A => Boolean): Boolean
Implicitly added by option2Iterable

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: A => U): Unit
Implicitly added by option2Iterable

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[A]): Iterable[A]
Implicitly added by option2Iterable
def groupBy[K](f: A => K): Map[K, Iterable[A]]
Implicitly added by option2Iterable

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: A => K)(f: A => B): Map[K, Iterable[B]]
Implicitly added by option2Iterable

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: A => K)(f: A => B)(reduce: (B, B) => B): Map[K, B]
Implicitly added by option2Iterable

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[Iterable[A]]
Implicitly added by option2Iterable

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: A
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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: Iterable[A]
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

Tests whether the collection is empty.

Tests whether the collection is empty.

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

Returns

true if the collection contains no elements, false otherwise.

Inherited from
IterableOnceOps
Implicitly added by option2Iterable

Iterator can be used only once

Iterator can be used only once

Inherited from
IterableOnce
Implicitly added by option2Iterable
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
def last: A
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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 map[B](f: A => B): Iterable[B]
Implicitly added by option2Iterable
Inherited from
IterableOps
def max[B >: A](ord: Ordering[B]): A
Implicitly added by option2Iterable

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: A => B)(cmp: Ordering[B]): A
Implicitly added by option2Iterable

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: A => B)(cmp: Ordering[B]): Option[A]
Implicitly added by option2Iterable

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 >: A](ord: Ordering[B]): Option[A]
Implicitly added by option2Iterable

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 >: A](ord: Ordering[B]): A
Implicitly added by option2Iterable

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: A => B)(cmp: Ordering[B]): A
Implicitly added by option2Iterable

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: A => B)(cmp: Ordering[B]): Option[A]
Implicitly added by option2Iterable

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 >: A](ord: Ordering[B]): Option[A]
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable
@deprecatedOverriding("nonEmpty is defined as !isEmpty; override isEmpty instead", "2.13.0")
Implicitly added by option2Iterable

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: A => Boolean): (Iterable[A], Iterable[A])
Implicitly added by option2Iterable

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: A => Either[A1, A2]): (Iterable[A1], Iterable[A2])
Implicitly added by option2Iterable

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 >: A](num: Numeric[B]): B
Implicitly added by option2Iterable

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

The size of this product.

The size of this product.

Returns

for a product A(x1, ..., xk), returns k

Inherited from
Product
def productElement(n: Int): Any

The nth element of this product, 0-based.

The nth element of this product, 0-based. In other words, for a product A(x1, ..., xk), returns x(n+1) where 0 <= n < k.

Value Params
n

the index of the element to return

Returns

the element n elements after the first element

Throws
IndexOutOfBoundsException

if the n is out of range(n < 0 || n >= productArity).

Inherited from
Product

The name of the nth element of this product, 0-based.

The name of the nth element of this product, 0-based. In the default implementation, an empty string.

Value Params
n

the index of the element name to return

Returns

the name of the specified element

Throws
IndexOutOfBoundsException

if the n is out of range(n < 0 || n >= productArity).

Inherited from
Product

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

A string used in the toString methods of derived classes.

A string used in the toString methods of derived classes. Implementations may override this method to prepend a string prefix to the result of toString methods.

Returns

in the default implementation, the empty string

Inherited from
Product
def reduce[B >: A](op: (B, B) => B): B
Implicitly added by option2Iterable

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 >: A](op: (B, A) => B): B
Implicitly added by option2Iterable

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 >: A](op: (B, A) => B): Option[B]
Implicitly added by option2Iterable

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 >: A](op: (B, B) => B): Option[B]
Implicitly added by option2Iterable

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 >: A](op: (A, B) => B): B
Implicitly added by option2Iterable

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 >: A](op: (A, B) => B): Option[B]
Implicitly added by option2Iterable

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[A]
Implicitly added by option2Iterable
Inherited from
IterableOnceOps
def scan[B >: A](z: B)(op: (B, B) => B): Iterable[B]
Implicitly added by option2Iterable

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, A) => B): Iterable[B]
Implicitly added by option2Iterable
Inherited from
IterableOps
def scanRight[B](z: B)(op: (A, B) => B): Iterable[B]
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable

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): Iterable[A]
Implicitly added by option2Iterable
Inherited from
IterableOps
def sliding(size: Int, step: Int): Iterator[Iterable[A]]
Implicitly added by option2Iterable

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[Iterable[A]]
Implicitly added by option2Iterable

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: A => Boolean): (Iterable[A], Iterable[A])
Implicitly added by option2Iterable
Inherited from
IterableOps
def stepper[S <: Stepper[_]](shape: StepperShape[A, S]): S
Implicitly added by option2Iterable

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 stepper[S <: Stepper[_]](shape: StepperShape[A, 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 >: A](num: Numeric[B]): B
Implicitly added by option2Iterable

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: Iterable[A]
Implicitly added by option2Iterable

The rest of the collection without its first element.

The rest of the collection without its first element.

Inherited from
IterableOps
Implicitly added by option2Iterable

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): Iterable[A]
Implicitly added by option2Iterable
Inherited from
IterableOps
def takeRight(n: Int): Iterable[A]
Implicitly added by option2Iterable

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: A => Boolean): Iterable[A]
Implicitly added by option2Iterable

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
def to[C1](factory: Factory[A, C1]): C1
Implicitly added by option2Iterable

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 >: A](`evidence$1`: ClassTag[B]): Array[B]
Implicitly added by option2Iterable

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 >: A]: Buffer[B]
Implicitly added by option2Iterable
Inherited from
IterableOnceOps
Implicitly added by option2Iterable
Inherited from
IterableOnceOps
def toList: List[A]
Implicitly added by option2Iterable
Inherited from
IterableOnceOps
def toMap[K, V](ev: A <:< (K, V)): Map[K, V]
Implicitly added by option2Iterable
Inherited from
IterableOnceOps
def toSeq: Seq[A]
Implicitly added by option2Iterable
Returns

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

Inherited from
IterableOnceOps
def toSet[B >: A]: Set[B]
Implicitly added by option2Iterable
Inherited from
IterableOnceOps
Implicitly added by option2Iterable
Inherited from
IterableOnceOps
def transpose[B](asIterable: A => Iterable[B]): Iterable[Iterable[B]]
Implicitly added by option2Iterable

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: A => (A1, A2)): (Iterable[A1], Iterable[A2])
Implicitly added by option2Iterable

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: A => (A1, A2, A3)): (Iterable[A1], Iterable[A2], Iterable[A3])
Implicitly added by option2Iterable

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
def view: View[A]
Implicitly added by option2Iterable

A view over the elements of this collection.

A view over the elements of this collection.

Inherited from
IterableOps
def withFilter(p: A => Boolean): WithFilter[A, [A] =>> Iterable[A]]
Implicitly added by option2Iterable

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]): Iterable[(A, B)]
Implicitly added by option2Iterable

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 >: A, B](that: Iterable[B], thisElem: A1, thatElem: B): Iterable[(A1, B)]
Implicitly added by option2Iterable

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
Implicitly added by option2Iterable
Inherited from
IterableOps

Deprecated and Inherited methods

@deprecated("Use ++ instead of ++: for collections of type Iterable", "2.13.0")
def ++:[B >: A](that: IterableOnce[B]): Iterable[B]
Implicitly added by option2Iterable
Deprecated
Inherited from
IterableOps
@deprecated("Use foldLeft instead of /:", "2.13.0") @inline
final def /:[B](z: B)(op: (B, A) => B): B
Implicitly added by option2Iterable
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use foldRight instead of :\\", "2.13.0") @inline
final def :\[B](z: B)(op: (A, B) => B): B
Implicitly added by option2Iterable
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, A) => B, combop: (B, B) => B): B
Implicitly added by option2Iterable
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use iterableFactory instead", "2.13.0") @deprecatedOverriding("Use iterableFactory instead", "2.13.0") @inline
Implicitly added by option2Iterable
Deprecated
Inherited from
IterableOps
@deprecated("Use `dest ++= coll` instead", "2.13.0") @inline
final def copyToBuffer[B >: A](dest: Buffer[B]): Unit
Implicitly added by option2Iterable
Deprecated
Inherited from
IterableOnceOps
@deprecated("Check .knownSize instead of .hasDefiniteSize for more actionable information (see scaladoc for details)", "2.13.0")
Implicitly added by option2Iterable

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: Iterable[A]
Implicitly added by option2Iterable
Deprecated
Inherited from
IterableOps
@deprecated("Use .iterator instead of .toIterator", "2.13.0") @inline
final def toIterator: Iterator[A]
Implicitly added by option2Iterable
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use .to(LazyList) instead of .toStream", "2.13.0") @inline
final def toStream: Stream[A]
Implicitly added by option2Iterable
Deprecated
Inherited from
IterableOnceOps
@deprecated("Use toIterable instead", "2.13.0")
Implicitly added by option2Iterable

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[A]
Implicitly added by option2Iterable

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