Type PartialFunction

[pawaclawczyk]

Type partial function represents a function which is undefined for some elements of the domain.

Example

f(x) = 42 / x is not defined at x equal 0

Minimal interface

interface PartialFunction
{
    public function isDefinedAt($x): bool;
    public function __invoke($x);
}

Maybe some additional logic and encapsulation in trait could be a good idea.
TDB