baethon / union
Union type for PHP
Requires
- php: >=7.1
Requires (Dev)
- friendsofphp/php-cs-fixer: ^2.12
- phpunit/phpunit: ^7.2
- squizlabs/php_codesniffer: ^3.3
This package is auto-updated.
Last update: 2024-11-24 22:38:38 UTC
README
Provides utilities to define tagged unions.
Tagged unions?
I'm not good with words, yet folks from Folktale describe it nicely:
Modelling data is important for a range of reasons. From performance to correctness to safety. Tagged unions give you a way of modelling choices that forces the correct handling of them, unlike predicate-based branching, such as the one used by if statements and other common control flow structures.
Installation
composer require baethon/union
Usage
To create a tag union it's required to create a class which extends Baethon\Union\AbstractUnion
.
class Maybe extends \Baethon\Union\AbstractUnion { }
Also you need to define tags which will represent state of the union.
class Maybe extends \Baethon\Union\AbstractUnion { const SOME = 'Some:x'; const NONE = 'None'; }
Signatures
Each tag has a definition (called signature), which can be defined using following syntax:
{Name}[:[param1[, param2[, ...[, paramN]]]]]
Parameters define whether a tag will hold any value(s) (called arguments). They're optional.
Working with unions
Union can be invoked using static constructor:
$some = Maybe::Some(1);
To work with the state of the union you should use matchWith()
. It will return the value returned by the matching callback:
function addTen(Maybe $maybe) { return $maybe->matchWith([ 'Some' => function ($x) { return $x + 10; }, 'None' => function () { throw new \Exception('Sorry, can\'t add a number to nothing'); } ]); } addTen($some); // 11
matchWith()
will check if all possible branches are mapped:
- if a tag is not covered by map
UnderflowException
will be thrown - if map covers more tags than defined ones it will throw 'OverflowException'.
It's possible to use wildcard map to cover all other cases:
$some->matchWith([ '*' => function () { return 100; } ]); // 100
You can use defined const values in mapping:
$some->matchWith([ Maybe::SOME => function () {}, Maybe::NONE => function () {} ]);
Testing
./vendor/bin/phpunit