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Identity.md

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Identity

The identity data structure is quite a trivial one, working just as a wrapper around a given type.

Constructors

The only constructor of Identity is wrap, which just wraps a value

/**
 * @template A
 */
final class Identity
{
    /**
     * @template B
     * @param B $b
     * @return IO<B>
     */
    public static function wrap($b): self
}

Synthetically, its type is

wrap :: B -> Identity<B>

Eliminators

The only eliminator for Identity is unwrap which just removes the Identity layer

    /**
     * @return A
     */
    public function unwrap()

Its simplified type is

unwrap :: Identity A -> A

Interpretation as an effect

The Identity datatype actually describes the absence of effects.

Typeclass instances

  • IdentityApplicative
  • IdentityApply
  • IdentityFoldable
  • IdentityFunctor
  • IdentityMonad
  • IdentityTraversable