Algorithm W in PHP

Introduction

Yet another fascinating concept to explore - type interference.

Algorithm W was implemented in PHP, and is based on Martin Grabmüller work [1].

Project uses the php-functional library [2] to simplify implementation, and make it closer to Haskell.

Next step is to use gathered experience it the typed-config project [3], with is aiming to make configuration type safe, self-documenting, easy to extend and dead-simple to use.

Sneak peek of one of many test cases can be interpreted

'let id = (x -> let y = x in y) in id id ' => [
    'expression' => new ELet(
        'id',
        new EAbs(
            'x',
            new ELet(
                'y',
                new EVar('x'),
                new EVar('y')
            )
        ),
        new EApp(
            new EVar('id'),
            new EVar('id')
        )
    ),
    'expected' => '(a5 -> a5)',
],

References

• [1] Algorithm W Step by Step
• [2] php-functional
• [3] typed-config