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<?php declare(strict_types=1);
namespace Dryist;
/**
* Create a modifier that always returns the same value.
*
* Also known as the Kestrel or "K" combinator.
* @see https://en.wikipedia.org/wiki/SKI_combinator_calculus
* @param mixed $x
* @return callable () => x
*/
function always($x): callable
{
return function () use ($x) {
return $x;
};
}
* Create a composition of two modifiers.
* Also known as the Substition or "S" combinator.
* @return callable (z) => x(y(z))
function compose(callable $x, callable $y): callable
return function ($z) use ($x, $y) {
return $x($y($z));
* @alias identity()
function id($x)
return identity($x);
* Return any given variable.
* Also known as the Identity or "I" combinator.
* @return mixed The value of $x
function identity($x)
* Create a negated predicate.
* @return callable (y) => ! x(y)
function invert(callable $x): callable
return function ($y) use ($x): bool {
return ! $x($y);
dryist /
functions
