Scala Library
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scala/Option.scala
]
sealed abstract
class
Option[+A]
extends
ProductOption
are either instances of case class Some
or it is case
object None
.Method Summary | |
def
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exists
(p : (A) => Boolean) : Boolean
If the option is nonempty, p(value), otherwise false.
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def
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filter
(p : (A) => Boolean) : Option[A]
If the option is nonempty and the given predicate
p
yields false on its value, return None .
Otherwise return the option value itself. |
def
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flatMap
[B](f : (A) => Option[B]) : Option[B]
If the option is nonempty, return a function applied to its value.
Otherwise return None.
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def
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foreach
[U](f : (A) => U) : Unit
Apply the given procedure
f to the option's value,
if it is nonempty. Do nothing if it is empty. |
abstract def
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get
: A
get the value of this option.
@requires that the option is nonEmpty.
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def
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getOrElse
[B >: A](default : => B) : B
If the option is nonempty return its value,
otherwise return the result of evaluating a default expression.
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def
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isDefined
: Boolean
True if the option is a
Some (...) false otherwise. |
abstract def
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isEmpty
: Boolean
True if the option is the
None value, false otherwise. |
def
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iterator
: Iterator[A]
An singleton iterator returning the option's value if it is nonempty
or the empty iterator if the option is empty.
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def
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map
[B](f : (A) => B) : Option[B]
If the option is nonempty, return a function applied to its value,
wrapped in a Some i.e.
Some(f(this.get)) .
Otherwise return None . |
def
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orElse
[B >: A](alternative : => Option[B]) : Option[B]
If the option is nonempty return it,
otherwise return the result of evaluating an alternative expression.
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def
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orNull
[A1 >: A](implicit ev : <:<[Null, A1]) : A1
The option's value if it is nonempty, or
null if it is empty.
The use of null of course is discouraged, but code written to use Options
often must interface with code which expects and returns nulls. |
def
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partialMap
[B](pf : PartialFunction[Any, B]) : Option[B]
If the given partial function
pf is defined for the
option's value, apply it to the value. Otherwise, None. |
def
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toLeft
[X](right : => X) : Product with Either[A, X]
An
Either that is a Right with the given argument
right if this is empty, or a Left if this is nonempty with the
option's value. |
def
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toList
: List[A]
A singleton list containing the option's value if it is nonempty
or the empty list if the option is empty.
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def
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toRight
[X](left : => X) : Product with Either[X, A]
An
Either that is a Left with the given argument
left if this is empty, or a Right if this is nonempty with the
option's value. |
Methods inherited from Product | |
productElement (abstract), productArity (abstract), productIterator, productElements, productPrefix |
Methods inherited from AnyRef | |
getClass, hashCode, equals, clone, toString, notify, notifyAll, wait, wait, wait, finalize, ==, !=, eq, ne, synchronized |
Methods inherited from Any | |
==, !=, isInstanceOf, asInstanceOf |
Methods inherited from Equals | |
canEqual (abstract) |
Method Details |
abstract
def
isEmpty : Boolean
None
value, false otherwise.
def
isDefined : Boolean
Some
(...) false otherwise.abstract
def
get : A
default -
the default expression.null
if it is empty.
The use of null of course is discouraged, but code written to use Options
often must interface with code which expects and returns nulls.Some(f(this.get))
.
Otherwise return None
.f -
the function to applyf -
the function to applyp
yields false
on its value, return None
.
Otherwise return the option value itself.p -
the predicate used for testing.p -
the predicate to testf
to the option's value,
if it is nonempty. Do nothing if it is empty.f -
the procedure to apply.
def
partialMap[B](pf : PartialFunction[Any, B]) : Option[B]
pf
is defined for the
option's value, apply it to the value. Otherwise, None.pf -
the partial function.alternative -
the alternative expression.Either
that is a Left
with the given argument
left
if this is empty, or a Right
if this is nonempty with the
option's value.Either
that is a Right
with the given argument
right
if this is empty, or a Left
if this is nonempty with the
option's value.
Scala Library
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