PartialFunction
Related Docs:
object PartialFunction
| package scala
Apply the body of this function to the argument.
Apply the body of this function to the argument.
the result of function application.
Checks if a value is contained in the function's domain.
Checks if a value is contained in the function's domain.
the value to test
true, iff x is in the domain of this function, false otherwise.
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.
the result type of the transformation function.
the transformation function
a partial function with the same domain as this partial function, which maps
arguments x to k(this(x)).
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:
orElse/andThen chains does not lead to
excessive apply/isDefinedAt evaluationlift and unlift do not evaluate source functions twice on each invocationrunWith 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.
the function argument
the fallback function
the result of this function or fallback function application.
2.10
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.
the type to which function g can be applied
a function A => T1
a new function f such that f(x) == apply(g(x))
Turns this partial function into a plain function returning an Option result.
Turns this partial function into a plain function returning an Option result.
a function that takes an argument x to Some(this(x)) if this
is defined for x, and to None otherwise.
Function.unlift
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.
the argument type of the fallback function
the result type of the fallback function
the fallback function
a partial function which has as domain the union of the domains
of this partial function and that. The resulting partial function
takes x to this(x) where this is defined, and to that(x) where it is not.
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.
the action function
a function which maps arguments x to isDefinedAt(x). The resulting function
runs action(this(x)) where this is defined.
2.10
applyOrElse.
A partial function of type
PartialFunction[A, B]is a unary function where the domain does not necessarily include all values of typeA. The functionisDefinedAtallows to test dynamically if a value is in the domain of the function.Even if
isDefinedAtreturns true for ana: A, callingapply(a)may still throw an exception, so the following code is legal:It is the responsibility of the caller to call
isDefinedAtbefore callingapply, because ifisDefinedAtis false, it is not guaranteedapplywill throw an exception to indicate an error condition. If an exception is not thrown, evaluation may result in an arbitrary value.The main distinction between
PartialFunctionand scala.Function1 is that the user of aPartialFunctionmay choose to do something different with input that is declared to be outside its domain. For example:1.0, 16/07/2003