scala.Option

sealed abstract class Option[+A] extends 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.

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")
}

• Self Type
  • Option [A]
• Annotations
  • @ SerialVersionUID ()
• Source
  • Option.scala - Blame
  • Option.scala - History
• Version
  • 1.1, 16/01/2007
• 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.

Type Members

class WithFilter extends AnyRef

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.

• Source
  • Option.scala - Blame
  • Option.scala - History

Abstract Value Members From scala.Equals

abstract 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. See Programming in Scala, Chapter 28 for discussion and design.

• that
  • the value being probed for possible equality
• returns
  • true if this instance can possibly equal that , otherwise false
• Definition Classes
  • Equals

(defined at scala.Equals)

Concrete Value Members From scala.Option

abstract def get: A

Returns the option’s value.

• Exceptions thrown
  • java.util.NoSuchElementException if the option is empty.
• Note
  • The option must be nonEmpty.

(defined at scala.Option)

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 None otherwise.

• pf
  • the partial function.
• returns
  • the result of applying pf to this scala.Option ‘s value (if possible), or None .
• Annotations
  • @ inline ()

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}

(defined at scala.Option)

final def contains[A1 >: A](elem: A1): Boolean

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

• 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"

(defined at scala.Option)

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. Otherwise, returns false.

• p
  • the predicate to test
• Annotations
  • @ inline ()

(defined at scala.Option)

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. Otherwise, return None .

• p
  • the predicate used for testing.
• Annotations
  • @ inline ()

(defined at scala.Option)

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. Otherwise, return None .

• p
  • the predicate used for testing.
• Annotations
  • @ inline ()

(defined at scala.Option)

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 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 ).

• f
  • the function to apply
• Annotations
  • @ inline ()
• See also
  • foreach map

(defined at scala.Option)

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

(defined at scala.Option)

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. Otherwise, evaluates expression ifEmpty .

• ifEmpty
  • the expression to evaluate if empty.
• f
  • the function to apply if nonempty.
• Annotations
  • @ inline ()
• Note
  • This is equivalent to scala.Option map f getOrElse ifEmpty .

(defined at scala.Option)

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.

• p
  • the predicate to test
• Annotations
  • @ inline ()

(defined at scala.Option)

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

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

• f
  • the procedure to apply.
• Annotations
  • @ inline ()
• See also
  • flatMap map

(defined at scala.Option)

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 .

• default
  • the default expression.
• Annotations
  • @ inline ()

(defined at scala.Option)

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. Otherwise return None .

• f
  • the function to apply
• Annotations
  • @ inline ()
• Note
  • This is similar to flatMap except here, f does not need to wrap its result in an scala.Option.
• See also
  • foreach flatMap

(defined at scala.Option)

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 .

• alternative
  • the alternative expression.
• Annotations
  • @ inline ()

(defined at scala.Option)

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

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.

• Annotations
  • @ inline ()

Example:

val initialText: Option[String] = getInitialText
val textField = new JComponent(initialText.orNull,20)

(defined at scala.Option)

final def toLeft[X](right: ⇒ X): util.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.

• right
  • the expression to evaluate and return if this is empty
• Annotations
  • @ inline ()
• See also
  • toRight

(defined at scala.Option)

final def toRight[X](left: ⇒ X): util.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.

• left
  • the expression to evaluate and return if this is empty
• Annotations
  • @ inline ()
• See also
  • toLeft

(defined at scala.Option)

final def withFilter(p: (A) ⇒ Boolean): WithFilter

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

• Annotations
  • @ inline ()

(defined at scala.Option)

Abstract Value Members From scala.Product

abstract def productElement(n: Int): Any

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

• n
  • the index of the element to return
• returns
  • the element n elements after the first element
• Definition Classes
  • Product
• Exceptions thrown *

(defined at scala.Product)

Concrete Value Members From Implicit scala.Option.option2Iterable

def ++:[B >: A, That](that: collection.Traversable[B])(implicit bf: CanBuildFrom[collection.Iterable[A], B, That]): That

As with ++ , returns a new collection containing the elements from the left operand followed by the elements from the right operand.

It differs from ++ in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.

Example:

scala> val x = List(1)
x: List[Int] = List(1)

scala> val y = LinkedList(2)
y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

scala> val z = x ++: y
z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)

This overload exists because: for the implementation of ++: we should reuse that of ++ because many collections override it with more efficient versions.

Since TraversableOnce has no ++ method, we have to implement that directly, but Traversable and down can use the overload.

• B
  • the element type of the returned collection.
• That
  • the class of the returned collection. Where possible, That is the same class as the current collection class Repr , but this depends on the element type B being admissible for that class, which means that an implicit instance of type CanBuildFrom[Repr, B, That] is found.
• that
  • the traversable to append.
• bf
  • an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and and the new element type B .
• returns
  • a new collection of type That which contains all elements of this iterable collection followed by all elements of that .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def ++:[B >: A, That](that: collection.TraversableOnce[B])(implicit bf: CanBuildFrom[collection.Iterable[A], B, That]): That

[use case]

As with ++ , returns a new collection containing the elements from the left operand followed by the elements from the right operand.

It differs from ++ in that the right operand determines the type of the resulting collection rather than the left one. Mnemonic: the COLon is on the side of the new COLlection type.

Example:

scala> val x = List(1)
x: List[Int] = List(1)

scala> val y = LinkedList(2)
y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)

scala> val z = x ++: y
z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)

• B
  • the element type of the returned collection.
• that
  • the traversable to append.
• returns
  • a new option which contains all elements of this option followed by all elements of that .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[collection.Iterable[A], B, That]): That

[use case]

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

Example:

scala> val a = List(1)
a: List[Int] = List(1)

scala> val b = List(2)
b: List[Int] = List(2)

scala> val c = a ++ b
c: List[Int] = List(1, 2)

scala> val d = List('a')
d: List[Char] = List(a)

scala> val e = c ++ d
e: List[AnyVal] = List(1, 2, a)

• B
  • the element type of the returned collection.
• that
  • the traversable to append.
• returns
  • a new option which contains all elements of this option followed by all elements of that .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def /:[B](z: B)(op: (B, A) ⇒ B): B

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

Note: /: is alternate syntax for foldLeft ; z /: xs is the same as xs foldLeft z .

Examples:

Note that the folding function used to compute b is equivalent to that used to compute c.

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

scala> val b = (5 /: a)(_+_)
b: Int = 15

scala> val c = (5 /: a)((x,y) => x + y)
c: Int = 15

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this iterable collection, going left to right with the start value z on the left:

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

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

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def :\[B](z: B)(op: (A, B) ⇒ B): B

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

Note: :\ is alternate syntax for foldRight ; xs :\ z is the same as xs foldRight z .

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.

Examples:

Note that the folding function used to compute b is equivalent to that used to compute c.

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

scala> val b = (a :\ 5)(_+_)
b: Int = 15

scala> val c = (a :\ 5)((x,y) => x + y)
c: Int = 15

• B
  • the result type of the binary operator.
• z
  • the start value
• op
  • the binary operator
• returns
  • the result of inserting op between consecutive elements of this iterable collection, going right to left with the start value z on the right:

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

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

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def addString(b: StringBuilder): StringBuilder

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

Example:

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

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

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

• b
  • the string builder to which elements are appended.
• returns
  • the string builder b to which elements were appended.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def addString(b: StringBuilder, sep: String): StringBuilder

Appends all elements of this iterable 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 iterable collection, separated by the string sep .

Example:

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

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

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

• b
  • the string builder to which elements are appended.
• sep
  • the separator string.
• returns
  • the string builder b to which elements were appended.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

Appends all elements of this iterable 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 iterable collection are separated by the string sep .

Example:

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

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

scala> a.addString(b , "List(" , ", " , ")")
res5: StringBuilder = List(1, 2, 3, 4)

• b
  • the string builder to which elements are appended.
• start
  • the starting string.
• sep
  • the separator string.
• end
  • the ending string.
• returns
  • the string builder b to which elements were appended.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def aggregate[B](z: ⇒ B)(seqop: (B, A) ⇒ B, combop: (B, B) ⇒ B): B

Aggregates the results of applying an operator to subsequent elements.

This is a more general form of fold and reduce . It is similar to foldLeft in that it doesn’t require the result to be a supertype of the element type. In addition, it allows parallel collections to be processed in chunks, and then combines the intermediate results.

aggregate splits the iterable collection into partitions and processes each partition by sequentially applying seqop , starting with z (like foldLeft ). Those intermediate results are then combined by using combop (like fold ). The implementation of this operation may operate on an arbitrary number of collection partitions (even 1), so combop may be invoked an arbitrary number of times (even 0).

As an example, consider summing up the integer values of a list of chars. The initial value for the sum is 0. First, seqop transforms each input character to an Int and adds it to the sum (of the partition). Then, combop just needs to sum up the intermediate results of the partitions:

List('a', 'b', 'c').aggregate(0)({ (sum, ch) => sum + ch.toInt }, { (p1, p2) => p1 + p2 })

• B
  • the type of accumulated results
• z
  • the initial value for the accumulated result of the partition - this will typically be the neutral element for the seqop operator (e.g. Nil for list concatenation or 0 for summation) and may be evaluated more than once
• seqop
  • an operator used to accumulate results within a partition
• combop
  • an associative operator used to combine results from different partitions
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

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

Note: may not terminate for infinite-sized collections.

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

• pf
  • the partial function
• returns
  • an option value containing pf applied to the first value for which it is defined, or None if none exists.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce

Example:

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

(added by implicit convertion: scala.Option.option2Iterable)

def companion: GenericCompanion[collection.Iterable]

The factory companion object that builds instances of class Iterable. (or its Iterable superclass where class Iterable is not a Seq .)

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • Iterable → GenIterable → Traversable → GenTraversable → GenericTraversableTemplate

(added by implicit convertion: scala.Option.option2Iterable)

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

[use case]

Copies the elements of this option to an array. Fills the given array xs with values of this option. Copying will stop once either the end of the current option is reached, or the end of the target array is reached.

• xs
  • the array to fill.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

[use case]

Copies the elements of this option to an array. Fills the given array xs with values of this option, beginning at index start . Copying will stop once either the end of the current option is reached, or the end of the target array is reached.

• xs
  • the array to fill.
• start
  • the starting index.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

[use case]

Copies the elements of this option to an array. Fills the given array xs with at most len elements of this option, starting at position start . Copying will stop once either the end of the current option is reached, or the end of the target array is reached, or len elements have been copied.

• xs
  • the array to fill.
• start
  • the starting index.
• len
  • the maximal number of elements to copy.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def copyToBuffer[B >: A](dest: Buffer[B]): Unit

Copies all elements of this iterable collection to a buffer.

Note: will not terminate for infinite-sized collections.

• dest
  • The buffer to which elements are copied.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def count(p: (A) ⇒ Boolean): Int

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

• p
  • the predicate used to test elements.
• returns
  • the number of elements satisfying the predicate p .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def drop(n: Int): collection.Iterable[A]

Selects all elements except first n ones.

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

• n
  • the number of elements to drop from this iterable collection.
• returns
  • a iterable collection consisting of all elements of this iterable collection except the first n ones, or else the empty iterable collection, if this iterable collection has less than n elements.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def dropRight(n: Int): collection.Iterable[A]

Selects all elements except last n ones.

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

• n
  • The number of elements to take
• 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.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike

(added by implicit convertion: scala.Option.option2Iterable)

def dropWhile(p: (A) ⇒ Boolean): collection.Iterable[A]

Drops longest prefix of elements that satisfy a predicate.

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

• returns
  • the longest suffix of this iterable collection whose first element does not satisfy the predicate p .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def find(p: (A) ⇒ Boolean): Option[A]

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

Note: may not terminate for infinite-sized collections.

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

• p
  • the predicate used to test elements.
• returns
  • an option value containing the first element in the iterable collection that satisfies p , or None if none exists.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike → TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this iterable collection, going left to right with the start value z on the left:

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

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

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this iterable collection, going right to left with the start value z on the right:

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

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

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def genericBuilder[B]: Builder[B, collection.Iterable[B]]

The generic builder that builds instances of Iterable at arbitrary element types.

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • GenericTraversableTemplate

(added by implicit convertion: scala.Option.option2Iterable)

def groupBy[K](f: (A) ⇒ K): Map[K, collection.Iterable[A]]

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

Note: this method is not re-implemented by views. This means when applied to a view it will always force the view and return a new iterable collection.

• K
  • the type of keys returned by the discriminator function.
• f
  • the discriminator function.
• returns
  • A map from keys to iterable collections such that the following invariant holds:

    (xs groupBy f)(k) = xs filter (x => f(x) == k)
    

That is, every key `k` is bound to a iterable collection of those elements
 `x` for which `f(x)` equals `k` .

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def grouped(size: Int): collection.Iterator[collection.Iterable[A]]

Partitions elements in fixed size iterable collections.

• size
  • the number of elements per group
• returns
  • An iterator producing iterable collections of size size , except the last will be less than size size if the elements don’t divide evenly.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike
• See also
  • scala.collection.Iterator, method grouped

(added by implicit convertion: scala.Option.option2Iterable)

def init: collection.Iterable[A]

Selects all elements except the last.

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

• returns
  • a iterable collection consisting of all elements of this iterable collection except the last one.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike
• Exceptions thrown
  • UnsupportedOperationException if the iterable collection is empty.

(added by implicit convertion: scala.Option.option2Iterable)

def inits: collection.Iterator[collection.Iterable[A]]

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 .

• returns
  • an iterator over all the inits of this iterable collection
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike

Example:

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

(added by implicit convertion: scala.Option.option2Iterable)

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

[use case]

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

• B
  • The result type of the function f.
• f
  • The measuring function.
• returns
  • the first element of this option with the largest value measured by function f.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

[use case]

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

• B
  • The result type of the function f.
• f
  • The measuring function.
• returns
  • the first element of this option with the smallest value measured by function f.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def mkString(sep: String): String

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

• sep
  • the separator string.
• returns
  • a string representation of this iterable collection. In the resulting string the string representations (w.r.t. the method toString ) of all elements of this iterable collection are separated by the string sep .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

Example:

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

(added by implicit convertion: scala.Option.option2Iterable)

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

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

• start
  • the starting string.
• sep
  • the separator string.
• end
  • the ending string.
• returns
  • a string representation of this iterable 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 iterable collection are separated by the string sep .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

Example:

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

(added by implicit convertion: scala.Option.option2Iterable)

def par: ParIterable[A]

Returns a parallel implementation of this collection.

For most collection types, this method creates a new parallel collection by copying all the elements. For these collection, par takes linear time. Mutable collections in this category do not produce a mutable parallel collection that has the same underlying dataset, so changes in one collection will not be reflected in the other one.

Specific collections (e.g. ParArray or mutable.ParHashMap ) override this default behaviour by creating a parallel collection which shares the same underlying dataset. For these collections, par takes constant or sublinear time.

All parallel collections return a reference to themselves.

• returns
  • a parallel implementation of this collection
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • Parallelizable

(added by implicit convertion: scala.Option.option2Iterable)

def partition(p: (A) ⇒ Boolean): (collection.Iterable[A], collection.Iterable[A])

Partitions this iterable collection in two iterable collections according to a predicate.

• p
  • the predicate on which to partition.
• returns
  • a pair of iterable collections: the first iterable collection consists of all elements that satisfy the predicate p and the second iterable collection consists of all elements that don’t. The relative order of the elements in the resulting iterable collections is the same as in the original iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

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

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • an option value containing the result of reduceLeft(op) if this iterable collection is nonempty, None otherwise.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this iterable collection, going left to right:

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

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

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this iterable collection is empty.

(added by implicit convertion: scala.Option.option2Iterable)

def reduceOption[A1 >: A](op: (A1, A1) ⇒ A1): Option[A1]

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

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

• A1
  • A type parameter for the binary operator, a supertype of A .
• op
  • A binary operator that must be associative.
• returns
  • An option value containing result of applying reduce operator op between all the elements if the collection is nonempty, and None otherwise.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • an option value containing the result of reduceRight(op) if this iterable collection is nonempty, None otherwise.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

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

Note: will not terminate for infinite-sized collections.

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

• B
  • the result type of the binary operator.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this iterable collection, going right to left:

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

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

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableOnce → GenTraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this iterable collection is empty.

(added by implicit convertion: scala.Option.option2Iterable)

def reduce[A1 >: A](op: (A1, A1) ⇒ A1): A1

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

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

• A1
  • A type parameter for the binary operator, a supertype of A .
• op
  • A binary operator that must be associative.
• returns
  • The result of applying reduce operator op between all the elements if the iterable collection is nonempty.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this iterable collection is empty.

(added by implicit convertion: scala.Option.option2Iterable)

def repr: collection.Iterable[A]

The collection of type iterable collection underlying this TraversableLike object. By default this is implemented as the TraversableLike object itself, but this can be overridden.

• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def sameElements[B >: A](that: GenIterable[B]): Boolean

[use case]

Checks if the other iterable collection contains the same elements in the same order as this option.

• that
  • the collection to compare with.
• returns
  • true , if both collections contain the same elements in the same order, false otherwise.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → GenIterableLike

(added by implicit convertion: scala.Option.option2Iterable)

def scanLeft[B, That](z: B)(op: (B, A) ⇒ B)(implicit bf: CanBuildFrom[collection.Iterable[A], B, That]): That

Produces a collection containing cumulative results of applying the operator 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.

• B
  • the type of the elements in the resulting collection
• That
  • the actual type of the resulting collection
• z
  • the initial value
• op
  • the binary operator applied to the intermediate result and the element
• bf
  • an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and and the new element type B .
• returns
  • collection with intermediate results
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def scanRight[B, That](z: B)(op: (A, B) ⇒ B)(implicit bf: CanBuildFrom[collection.Iterable[A], B, That]): That

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.

Example:

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

• B
  • the type of the elements in the resulting collection
• That
  • the actual type of the resulting collection
• z
  • the initial value
• op
  • the binary operator applied to the intermediate result and the element
• bf
  • an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and and the new element type B .
• returns
  • collection with intermediate results
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike
• Annotations
  • @migration
• Migration
  • (Changed in version 2.9.0) The behavior of scanRight has changed. The previous behavior can be reproduced with scanRight.reverse.

(added by implicit convertion: scala.Option.option2Iterable)

def scan[B >: A, That](z: B)(op: (B, B) ⇒ B)(implicit cbf: CanBuildFrom[collection.Iterable[A], B, That]): That

Computes a prefix scan of the elements of the collection.

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

• B
  • element type of the resulting collection
• That
  • type of the resulting collection
• z
  • neutral element for the operator op
• op
  • the associative operator for the scan
• cbf
  • combiner factory which provides a combiner
• returns
  • a new iterable collection containing the prefix scan of the elements in this iterable collection
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def seq: collection.Iterable[A]

A version of this collection with all of the operations implemented sequentially (i.e., in a single-threaded manner).

This method returns a reference to this collection. In parallel collections, it is redefined to return a sequential implementation of this collection. In both cases, it has O(1) complexity.

• returns
  • a sequential view of the collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • Iterable → GenIterable → Traversable → GenTraversable → Parallelizable → TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def slice(from: Int, until: Int): collection.Iterable[A]

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

from <= indexOf(x) < until

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

• returns
  • a iterable collection containing the elements greater than or equal to index from extending up to (but not including) index until of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def sliding(size: Int): collection.Iterator[collection.Iterable[A]]

Groups elements in fixed size blocks by passing a “sliding window” over them (as opposed to partitioning them, as is done in grouped.) “Sliding window” step is 1 by default.

• size
  • the number of elements per group
• returns
  • An iterator producing iterable collections of size size , except the last and the only element will be truncated if there are fewer elements than size.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike
• See also
  • scala.collection.Iterator, method sliding

(added by implicit convertion: scala.Option.option2Iterable)

def sliding(size: Int, step: Int): collection.Iterator[collection.Iterable[A]]

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

• size
  • the number of elements per group
• step
  • the distance between the first elements of successive groups
• returns
  • An iterator producing iterable collections of size size , except the last and the only element will be truncated if there are fewer elements than size.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike
• See also
  • scala.collection.Iterator, method sliding

(added by implicit convertion: scala.Option.option2Iterable)

def span(p: (A) ⇒ Boolean): (collection.Iterable[A], collection.Iterable[A])

Splits this iterable collection into a prefix/suffix pair according to a predicate.

Note: c span p is equivalent to (but possibly more efficient than) (c takeWhile p, c dropWhile p) , provided the evaluation of the predicate p does not cause any side-effects.

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

• returns
  • a pair consisting of the longest prefix of this iterable collection whose elements all satisfy p , and the rest of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def splitAt(n: Int): (collection.Iterable[A], collection.Iterable[A])

Splits this iterable collection into two at a given position. Note: c splitAt n is equivalent to (but possibly more efficient than) (c take n, c drop n) .

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

• n
  • the position at which to split.
• returns
  • a pair of iterable collections consisting of the first n elements of this iterable collection, and the other elements.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def tail: collection.Iterable[A]

Selects all elements except the first.

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

• returns
  • a iterable collection consisting of all elements of this iterable collection except the first one.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → GenTraversableLike
• Exceptions thrown
  • UnsupportedOperationException if the iterable collection is empty.

(added by implicit convertion: scala.Option.option2Iterable)

def tails: collection.Iterator[collection.Iterable[A]]

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
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike

Example:

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

(added by implicit convertion: scala.Option.option2Iterable)

def take(n: Int): collection.Iterable[A]

Selects first n elements.

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

• n
  • the number of elements to take from this iterable collection.
• returns
  • a iterable collection consisting only of the first n elements of this iterable collection, or else the whole iterable collection, if it has less than n elements.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def takeRight(n: Int): collection.Iterable[A]

Selects last n elements.

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

• n
  • the number of elements to take
• 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.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike

(added by implicit convertion: scala.Option.option2Iterable)

def takeWhile(p: (A) ⇒ Boolean): collection.Iterable[A]

Takes longest prefix of elements that satisfy a predicate.

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

• returns
  • the longest prefix of this iterable collection whose elements all satisfy the predicate p .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

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

Uses the contents of this iterable collection to create a new mutable buffer.

Note: will not terminate for infinite-sized collections.

• returns
  • a buffer containing all elements of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def toIndexedSeq: collection.immutable.IndexedSeq[A]

Converts this iterable collection to an indexed sequence.

Note: will not terminate for infinite-sized collections.

• returns
  • an indexed sequence containing all elements of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def toIterable: collection.Iterable[A]

Returns this iterable collection as an iterable collection.

A new collection will not be built; lazy collections will stay lazy.

Note: will not terminate for infinite-sized collections.

• returns
  • an Iterable containing all elements of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def toIterator: collection.Iterator[A]

Returns an Iterator over the elements in this iterable collection. Produces the same result as iterator .

Note: will not terminate for infinite-sized collections.

• returns
  • an Iterator containing all elements of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableOnce
• Annotations
  • @ deprecatedOverriding (message =…, since = “2.11.0”)

(added by implicit convertion: scala.Option.option2Iterable)

def toMap[T, U](implicit ev: <:<[A, (T, U)]): Map[T, U]

[use case]

Converts this option to a map. This method is unavailable unless the elements are members of Tuple2, each ((T, U)) becoming a key-value pair in the map. Duplicate keys will be overwritten by later keys: if this is an unordered collection, which key is in the resulting map is undefined.

• returns
  • a map of type immutable.Map[T, U] containing all key/value pairs of type (T, U) of this option.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def toSeq: collection.Seq[A]

Converts this iterable collection to a sequence. As with toIterable , it’s lazy in this default implementation, as this TraversableOnce may be lazy and unevaluated.

Note: will not terminate for infinite-sized collections.

• returns
  • a sequence containing all elements of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

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

Converts this iterable collection to a set.

Note: will not terminate for infinite-sized collections.

• returns
  • a set containing all elements of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableOnce → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def toStream: collection.immutable.Stream[A]

Converts this iterable collection to a stream.

• returns
  • a stream containing all elements of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike → GenTraversableOnce

(added by implicit convertion: scala.Option.option2Iterable)

def toTraversable: collection.Traversable[A]

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

Note: will not terminate for infinite-sized collections.

• returns
  • a Traversable containing all elements of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • TraversableLike → TraversableOnce → GenTraversableOnce
• Annotations
  • @ deprecatedOverriding (message =…, since = “2.11.0”)

(added by implicit convertion: scala.Option.option2Iterable)

def transpose[B](implicit asTraversable: (A) ⇒ GenTraversableOnce[B]): collection.Iterable[collection.Iterable[B]]

Transposes this iterable collection of traversable 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))

• B
  • the type of the elements of each traversable collection.
• asTraversable
  • an implicit conversion which asserts that the element type of this iterable collection is a Traversable .
• returns
  • a two-dimensional iterable collection of iterable collections which has as _ n_ th row the n th column of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • GenericTraversableTemplate
• Annotations
  • @migration
• Migration
  • (Changed in version 2.9.0) transpose throws an IllegalArgumentException if collections are not uniformly sized.
• Exceptions thrown
  • IllegalArgumentException if all collections in this iterable collection are not of the same size.

(added by implicit convertion: scala.Option.option2Iterable)

def unzip3[A1, A2, A3](implicit asTriple: (A) ⇒ (A1, A2, A3)): (collection.Iterable[A1], collection.Iterable[A2], collection.Iterable[A3])

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

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

• A1
  • the type of the first member of the element triples
• A2
  • the type of the second member of the element triples
• A3
  • the type of the third member of the element triples
• asTriple
  • an implicit conversion which asserts that the element type of this iterable collection is a triple.
• returns
  • a triple of iterable collections, containing the first, second, respectively third member of each element triple of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • GenericTraversableTemplate

(added by implicit convertion: scala.Option.option2Iterable)

def unzip[A1, A2](implicit asPair: (A) ⇒ (A1, A2)): (collection.Iterable[A1], collection.Iterable[A2])

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

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

• A1
  • the type of the first half of the element pairs
• A2
  • the type of the second half of the element pairs
• asPair
  • an implicit conversion which asserts that the element type of this iterable collection is a pair.
• returns
  • a pair of iterable collections, containing the first, respectively second half of each element pair of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • GenericTraversableTemplate

(added by implicit convertion: scala.Option.option2Iterable)

def view(from: Int, until: Int): IterableView[A, collection.Iterable[A]]

Creates a non-strict view of a slice of this iterable collection.

Note: the difference between view and slice is that view produces a view of the current iterable collection, whereas slice produces a new iterable collection.

Note: view(from, to) is equivalent to view.slice(from, to)

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

• from
  • the index of the first element of the view
• until
  • the index of the element following the view
• returns
  • a non-strict view of a slice of this iterable collection, starting at index from and extending up to (but not including) index until .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def view: IterableView[A, collection.Iterable[A]]

Creates a non-strict view of this iterable collection.

• returns
  • a non-strict view of this iterable collection.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → TraversableLike

(added by implicit convertion: scala.Option.option2Iterable)

def zipAll[B, A1 >: A, That](that: GenIterable[B], thisElem: A1, thatElem: B)(implicit bf: CanBuildFrom[collection.Iterable[A], (A1, B), That]): That

[use case]

Returns a option formed from this option 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.

• B
  • the type of the second half of the returned pairs
• that
  • The iterable providing the second half of each result pair
• thisElem
  • the element to be used to fill up the result if this option is shorter than that .
• thatElem
  • the element to be used to fill up the result if that is shorter than this option.
• returns
  • a new option containing pairs consisting of corresponding elements of this option and that . The length of the returned collection is the maximum of the lengths of this option and that . If this option is shorter than that , thisElem values are used to pad the result. If that is shorter than this option, thatElem values are used to pad the result.
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → GenIterableLike

(added by implicit convertion: scala.Option.option2Iterable)

def zip[A1 >: A, B, That](that: GenIterable[B])(implicit bf: CanBuildFrom[collection.Iterable[A], (A1, B), That]): That

[use case]

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

• B
  • the type of the second half of the returned pairs
• that
  • The iterable providing the second half of each result pair
• returns
  • a new option containing pairs consisting of corresponding elements of this option and that . The length of the returned collection is the minimum of the lengths of this option and that .
• Implicit information
  • This member is added by an implicit conversion from Option [A] to Iterable [ A] performed by method option2Iterable in scala.Option.
• Definition Classes
  • IterableLike → GenIterableLike (added by implicit convertion: scala.Option.option2Iterable)

Full Source:

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala

object Option {

  import scala.language.implicitConversions

  /** An implicit conversion that converts an option to an iterable value
   */
  implicit def option2Iterable[A](xo: Option[A]): Iterable[A] = xo.toList

  /** An Option factory which creates Some(x) if the argument is not null,
   *  and None if it is null.
   *
   *  @param  x the value
   *  @return   Some(value) if value != null, None if value == null
   */
  def apply[A](x: A): Option[A] = if (x == null) None else Some(x)

  /** An Option factory which returns `None` in a manner consistent with
   *  the collections hierarchy.
   */
  def empty[A] : Option[A] = None
}

/** Represents optional values. Instances of `Option`
 *  are either an instance of $some or the object $none.
 *
 *  The most idiomatic way to use an $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 $option values without
 *  having to check for the existence of a value.
 *
 *  A less-idiomatic way to use $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")
 *  }
 *  }}}
 *
 *  @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.
 *
 *  @author  Martin Odersky
 *  @author  Matthias Zenger
 *  @version 1.1, 16/01/2007
 *  @define none `None`
 *  @define some [[scala.Some]]
 *  @define option [[scala.Option]]
 *  @define p `p`
 *  @define f `f`
 *  @define coll option
 *  @define Coll `Option`
 *  @define orderDependent
 *  @define orderDependentFold
 *  @define mayNotTerminateInf
 *  @define willNotTerminateInf
 *  @define collectExample
 *  @define undefinedorder
 *  @define thatinfo the class of the returned collection. In the standard library configuration, `That` is `Iterable[B]`
 *  @define bfinfo an implicit value of class `CanBuildFrom` which determines the result class `That` from the current
 *    representation type `Repr` and the new element type `B`.
 */
@SerialVersionUID(-114498752079829388L) // value computed by serialver for 2.11.2, annotation added in 2.11.4
sealed abstract class Option[+A] extends Product with Serializable {
  self =>

  /** Returns true if the option is $none, false otherwise.
   */
  def isEmpty: Boolean

  /** Returns true if the option is an instance of $some, false otherwise.
   */
  def isDefined: Boolean = !isEmpty

  /** Returns the option's value.
   *  @note The option must be nonEmpty.
   *  @throws java.util.NoSuchElementException if the option is empty.
   */
  def get: A

  /** Returns the option's value if the option is nonempty, otherwise
   * return the result of evaluating `default`.
   *
   *  @param default  the default expression.
   */
  @inline final def getOrElse[B >: A](default: => B): B =
    if (isEmpty) default else this.get

  /** 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
   * $option must often interface with code that expects and returns nulls.
   * @example {{{
   * val initialText: Option[String] = getInitialText
   * val textField = new JComponent(initialText.orNull,20)
   * }}}
   */
  @inline final def orNull[A1 >: A](implicit ev: Null <:< A1): A1 = this getOrElse ev(null)

  /** Returns a $some containing the result of applying $f to this $option's
   * value if this $option is nonempty.
   * Otherwise return $none.
   *
   *  @note This is similar to `flatMap` except here,
   *  $f does not need to wrap its result in an $option.
   *
   *  @param  f   the function to apply
   *  @see flatMap
   *  @see foreach
   */
  @inline final def map[B](f: A => B): Option[B] =
    if (isEmpty) None else Some(f(this.get))

  /** Returns the result of applying $f to this $option's
   *  value if the $option is nonempty.  Otherwise, evaluates
   *  expression `ifEmpty`.
   *
   *  @note This is equivalent to `$option map f getOrElse ifEmpty`.
   *
   *  @param  ifEmpty the expression to evaluate if empty.
   *  @param  f       the function to apply if nonempty.
   */
  @inline final def fold[B](ifEmpty: => B)(f: A => B): B =
    if (isEmpty) ifEmpty else f(this.get)

  /** Returns the result of applying $f to this $option's value if
   * this $option is nonempty.
   * Returns $none if this $option is empty.
   * Slightly different from `map` in that $f is expected to
   * return an $option (which could be $none).
   *
   *  @param  f   the function to apply
   *  @see map
   *  @see foreach
   */
  @inline final def flatMap[B](f: A => Option[B]): Option[B] =
    if (isEmpty) None else f(this.get)

  def flatten[B](implicit ev: A <:< Option[B]): Option[B] =
    if (isEmpty) None else ev(this.get)

  /** Returns this $option if it is nonempty '''and''' applying the predicate $p to
   * this $option's value returns true. Otherwise, return $none.
   *
   *  @param  p   the predicate used for testing.
   */
  @inline final def filter(p: A => Boolean): Option[A] =
    if (isEmpty || p(this.get)) this else None

  /** Returns this $option if it is nonempty '''and''' applying the predicate $p to
   * this $option's value returns false. Otherwise, return $none.
   *
   *  @param  p   the predicate used for testing.
   */
  @inline final def filterNot(p: A => Boolean): Option[A] =
    if (isEmpty || !p(this.get)) this else None

  /** Returns false if the option is $none, true otherwise.
   *  @note   Implemented here to avoid the implicit conversion to Iterable.
   */
  final def nonEmpty = isDefined

  /** Necessary to keep $option from being implicitly converted to
   *  [[scala.collection.Iterable]] in `for` comprehensions.
   */
  @inline final def withFilter(p: A => Boolean): WithFilter = new WithFilter(p)

  /** 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.
   */
  class WithFilter(p: A => Boolean) {
    def map[B](f: A => B): Option[B] = self filter p map f
    def flatMap[B](f: A => Option[B]): Option[B] = self filter p flatMap f
    def foreach[U](f: A => U): Unit = self filter p foreach f
    def withFilter(q: A => Boolean): WithFilter = new WithFilter(x => p(x) && q(x))
  }

  /** Tests whether the option contains a given value as an element.
   *
   *  @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"
   *  }}}
   *
   *  @param elem the element to test.
   *  @return `true` if the option has an element that is equal (as
   *  determined by `==`) to `elem`, `false` otherwise.
   */
  final def contains[A1 >: A](elem: A1): Boolean =
    !isEmpty && this.get == elem

  /** Returns true if this option is nonempty '''and''' the predicate
   * $p returns true when applied to this $option's value.
   * Otherwise, returns false.
   *
   *  @param  p   the predicate to test
   */
  @inline final def exists(p: A => Boolean): Boolean =
    !isEmpty && p(this.get)

  /** Returns true if this option is empty '''or''' the predicate
   * $p returns true when applied to this $option's value.
   *
   *  @param  p   the predicate to test
   */
  @inline final def forall(p: A => Boolean): Boolean = isEmpty || p(this.get)

  /** Apply the given procedure $f to the option's value,
   *  if it is nonempty. Otherwise, do nothing.
   *
   *  @param  f   the procedure to apply.
   *  @see map
   *  @see flatMap
   */
  @inline final def foreach[U](f: A => U) {
    if (!isEmpty) f(this.get)
  }

  /** Returns a $some containing the result of
   * applying `pf` to this $option's contained
   * value, '''if''' this option is
   * nonempty '''and''' `pf` is defined for that value.
   * Returns $none otherwise.
   *
   *  @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}
   *  }}}
   *
   *  @param  pf   the partial function.
   *  @return the result of applying `pf` to this $option's
   *  value (if possible), or $none.
   */
  @inline final def collect[B](pf: PartialFunction[A, B]): Option[B] =
    if (!isEmpty) pf.lift(this.get) else None

  /** Returns this $option if it is nonempty,
   *  otherwise return the result of evaluating `alternative`.
   *  @param alternative the alternative expression.
   */
  @inline final def orElse[B >: A](alternative: => Option[B]): Option[B] =
    if (isEmpty) alternative else this

  /** Returns a singleton iterator returning the $option's value
   * if it is nonempty, or an empty iterator if the option is empty.
   */
  def iterator: Iterator[A] =
    if (isEmpty) collection.Iterator.empty else collection.Iterator.single(this.get)

  /** Returns a singleton list containing the $option's value
   * if it is nonempty, or the empty list if the $option is empty.
   */
  def toList: List[A] =
    if (isEmpty) List() else new ::(this.get, Nil)

  /** Returns a [[scala.util.Left]] containing the given
   * argument `left` if this $option is empty, or
   * a [[scala.util.Right]] containing this $option's value if
   * this is nonempty.
   *
   * @param left the expression to evaluate and return if this is empty
   * @see toLeft
   */
  @inline final def toRight[X](left: => X) =
    if (isEmpty) Left(left) else Right(this.get)

  /** Returns a [[scala.util.Right]] containing the given
   * argument `right` if this is empty, or
   * a [[scala.util.Left]] containing this $option's value
   * if this $option is nonempty.
   *
   * @param right the expression to evaluate and return if this is empty
   * @see toRight
   */
  @inline final def toLeft[X](right: => X) =
    if (isEmpty) Right(right) else Left(this.get)
}

/** Class `Some[A]` represents existing values of type
 *  `A`.
 *
 *  @author  Martin Odersky
 *  @version 1.0, 16/07/2003
 */
@SerialVersionUID(1234815782226070388L) // value computed by serialver for 2.11.2, annotation added in 2.11.4
final case class Some[+A](x: A) extends Option[A] {
  def isEmpty = false
  def get = x
}


/** This case object represents non-existent values.
 *
 *  @author  Martin Odersky
 *  @version 1.0, 16/07/2003
 */
@SerialVersionUID(5066590221178148012L) // value computed by serialver for 2.11.2, annotation added in 2.11.4
case object None extends Option[Nothing] {
  def isEmpty = true
  def get = throw new NoSuchElementException("None.get")
}