Class AbstractPartialFunction.AbstractPartialFunction

abstract class AbstractPartialFunction[-T1, +R] extends T1 => R with PartialFunction[T1, R]

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.

Concrete methods

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def apply(x: T1): R

Apply the body of this function to the argument.

Inherited methods

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def andThen[C](k: PartialFunction[R, C]): PartialFunction[A, C]

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.

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override def andThen[C](k: R => C): PartialFunction[A, C]

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).

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def applyOrElse[A1 <: T1, B1 >: R](x: A1, default: A1 => B1): B1

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.

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def compose[R](k: PartialFunction[R, T1]): PartialFunction[R, B]

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.

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def compose[A](g: A => T1): A => R

Composes two instances of Function1 in a new Function1, with this function applied last.

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def elementWise: ElementWiseExtractor[A, B]

Returns an extractor object with a unapplySeq method, which extracts each element of a sequence data.

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
}

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def isDefinedAt(x: T1): Boolean

Checks if a value is contained in the function's domain.

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def lift: A => Option[B]

Turns this partial function into a plain function returning an Option result.

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def orElse[A1 <: T1, B1 >: R](that: PartialFunction[A1, B1]): PartialFunction[A1, B1]

Composes this partial function with a fallback partial function which gets applied where this partial function is not defined.

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def runWith[U](action: R => U): A => Boolean

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.

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override def toString(): String

Returns a string representation of the object.

The default representation is platform dependent.

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def unapply(a: T1): Option[B]

Tries to extract a B from an A in a pattern matching expression.