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.
Value members
Concrete methods
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. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.
- Type Params
- C
the result type of the transformation function.
- Value Params
- k
the transformation function
- Returns
a partial function with the domain of this partial function narrowed by other partial function, which maps arguments
xtok(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 Params
- C
the result type of the transformation function.
- Value Params
- k
the transformation function
- Returns
a partial function with the domain of this partial function, possibly narrowed by the specified function, which maps arguments
xtok(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 Params
- default
the fallback function
- x
the function argument
- 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. It is highly recommended to call applyOrElse instead of isDefinedAt / apply for efficiency.
- Type Params
- R
the parameter type of the transformation function.
- Value Params
- k
the transformation function
- Returns
a partial function with the domain of other partial function narrowed by this partial function, which maps arguments
xtothis(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 Params
- A
the type to which function
gcan be applied
- Value Params
- g
a function A => T1
- Returns
a new function
fsuch 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.
- 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
Checks if a value is contained in the function's domain.
Checks if a value is contained in the function's domain.
- Value Params
- x
the value to test
- Returns
true, iffxis in the domain of this function,falseotherwise.- 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.
- Returns
a function that takes an argument
xtoSome(this(x))ifthisis defined forx, and toNoneotherwise.- 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 Params
- A1
the argument type of the fallback function
- B1
the result type of the fallback function
- Value Params
- that
the fallback function
- Returns
a partial function which has as domain the union of the domains of this partial function and
that. The resulting partial function takesxtothis(x)wherethisis 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 falseexcept 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 Params
- action
the action function
- Returns
a function which maps arguments
xtoisDefinedAt(x). The resulting function runsaction(this(x))wherethisis defined.- See also
applyOrElse.- Inherited from
- PartialFunction
- Source
- PartialFunction.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.
- Inherited from
- PartialFunction
- Source
- PartialFunction.scala