AbstractPartialFunction
AbstractPartialFunction
reformulates all operations of its supertrait PartialFunction
in terms of isDefinedAt
and applyOrElse
.
This allows more efficient implementations in many cases: - optimized orElse
method supports chained orElse
in linear time, and with no slow-down if the orElse
part is not needed. - optimized lift
method helps to avoid double evaluation of pattern matchers & guards of partial function literals.
This trait is used as a basis for implementation of all partial function literals.
Attributes
- Source
- AbstractPartialFunction.scala
- Graph
-
- Supertypes
- Self type
-
Members list
Value members
Concrete methods
Apply the body of this function to the argument.
Apply the body of this function to the argument.
Attributes
- Returns
-
the result of function application.
- Source
- AbstractPartialFunction.scala
Inherited methods
Composes this partial function with another partial function that gets applied to results of this partial function.
Composes this partial function with another partial function that gets applied to results of this partial function.
Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. For efficiency, it is recommended to call applyOrElse instead of isDefinedAt or apply.
Type parameters
- C
-
the result type of the transformation function.
Value parameters
- k
-
the transformation function
Attributes
- Returns
-
a partial function with the domain of this partial function narrowed by other partial function, which maps arguments
x
tok(this(x))
. - Inherited from:
- PartialFunction
- Source
- PartialFunction.scala
Composes this partial function with a transformation function that gets applied to results of this partial function.
Composes this partial function with a transformation function that gets applied to results of this partial function.
If the runtime type of the function is a PartialFunction
then the other andThen
method is used (note its cautions).
Type parameters
- C
-
the result type of the transformation function.
Value parameters
- k
-
the transformation function
Attributes
- Returns
-
a partial function with the domain of this partial function, possibly narrowed by the specified function, which maps arguments
x
tok(this(x))
. - Definition Classes
- Inherited from:
- PartialFunction
- Source
- PartialFunction.scala
Applies this partial function to the given argument when it is contained in the function domain.
Applies this partial function to the given argument when it is contained in the function domain. Applies fallback function where this partial function is not defined.
Note that expression pf.applyOrElse(x, default)
is equivalent to
if(pf isDefinedAt x) pf(x) else default(x)
except that applyOrElse
method can be implemented more efficiently. For all partial function literals the compiler generates an applyOrElse
implementation which avoids double evaluation of pattern matchers and guards. This makes applyOrElse
the basis for the efficient implementation for many operations and scenarios, such as:
- combining partial functions into orElse
/andThen
chains does not lead to excessive apply
/isDefinedAt
evaluation - lift
and unlift
do not evaluate source functions twice on each invocation - runWith
allows efficient imperative-style combining of partial functions with conditionally applied actions
For non-literal partial function classes with nontrivial isDefinedAt
method it is recommended to override applyOrElse
with custom implementation that avoids double isDefinedAt
evaluation. This may result in better performance and more predictable behavior w.r.t. side effects.
Value parameters
- default
-
the fallback function
- x
-
the function argument
Attributes
- Returns
-
the result of this function or fallback function application.
- Inherited from:
- PartialFunction
- Source
- PartialFunction.scala
Composes another partial function k
with this partial function so that this partial function gets applied to results of k
.
Composes another partial function k
with this partial function so that this partial function gets applied to results of k
.
Note that calling isDefinedAt on the resulting partial function may apply the first partial function and execute its side effect. For efficiency, it is recommended to call applyOrElse instead of isDefinedAt or apply.
Type parameters
- R
-
the parameter type of the transformation function.
Value parameters
- k
-
the transformation function
Attributes
- Returns
-
a partial function with the domain of other partial function narrowed by this partial function, which maps arguments
x
tothis(k(x))
. - Inherited from:
- PartialFunction
- Source
- PartialFunction.scala
Composes two instances of Function1
in a new Function1
, with this function applied last.
Composes two instances of Function1
in a new Function1
, with this function applied last.
Type parameters
- A
-
the type to which function
g
can be applied
Value parameters
- g
-
a function A => T1
Attributes
- Returns
-
a new function
f
such thatf(x) == apply(g(x))
- Inherited from:
- Function1
- Source
- Function1.scala
Returns an extractor object with a unapplySeq
method, which extracts each element of a sequence data.
Returns an extractor object with a unapplySeq
method, which extracts each element of a sequence data.
Attributes
- Example
-
val firstChar: String => Option[Char] = _.headOption Seq("foo", "bar", "baz") match { case firstChar.unlift.elementWise(c0, c1, c2) => println(s"$c0, $c1, $c2") // Output: f, b, b }
- Inherited from:
- PartialFunction
- Source
- PartialFunction.scala
Turns this partial function into a plain function returning an Option
result.
Turns this partial function into a plain function returning an Option
result.
Attributes
- Returns
-
a function that takes an argument
x
toSome(this(x))
ifthis
is defined forx
, and toNone
otherwise. - See also
-
Function.unlift
- Inherited from:
- PartialFunction
- Source
- PartialFunction.scala
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.
Type parameters
- A1
-
the argument type of the fallback function
- B1
-
the result type of the fallback function
Value parameters
- that
-
the fallback function
Attributes
- Returns
-
a partial function which has as domain the union of the domains of this partial function and
that
. The resulting partial function takesx
tothis(x)
wherethis
is defined, and tothat(x)
where it is not. - Inherited from:
- PartialFunction
- Source
- PartialFunction.scala
Composes this partial function with an action function which gets applied to results of this partial function.
Composes this partial function with an action function which gets applied to results of this partial function. The action function is invoked only for its side effects; its result is ignored.
Note that expression pf.runWith(action)(x)
is equivalent to
if(pf isDefinedAt x) { action(pf(x)); true } else false
except that runWith
is implemented via applyOrElse
and thus potentially more efficient. Using runWith
avoids double evaluation of pattern matchers and guards for partial function literals.
Value parameters
- action
-
the action function
Attributes
- Returns
-
a function which maps arguments
x
toisDefinedAt(x)
. The resulting function runsaction(this(x))
wherethis
is defined. - See also
-
applyOrElse
. - Inherited from:
- PartialFunction
- Source
- PartialFunction.scala
Returns a string representation of the object.
Returns a string representation of the object.
The default representation is platform dependent.
Attributes
- Returns
-
a string representation of the object.
- Definition Classes
- Inherited from:
- Function1
- Source
- Function1.scala
Tries to extract a B
from an A
in a pattern matching expression.
Tries to extract a B
from an A
in a pattern matching expression.
Attributes
- Inherited from:
- PartialFunction
- Source
- PartialFunction.scala
Inherited and Abstract methods
Checks if a value is contained in the function's domain.
Checks if a value is contained in the function's domain.
Value parameters
- x
-
the value to test
Attributes
- Returns
-
true
, iffx
is in the domain of this function,false
otherwise. - Inherited from:
- PartialFunction
- Source
- PartialFunction.scala