PHP code example of php-fp / php-fp-either

    
        
<?php
require_once('vendor/autoload.php');

/* Start to develop here. Best regards https://php-download.com/ */

    

php-fp / php-fp-either example snippets

use PhpFp\Either\Constructor\{Left, Right};

$login = function ($username, $password)
{
    if ($username != 'foo') {
        return new Left(
            'Invalid username'
        );
    }

    if ($password != 'bar') {
        return new Left(
            'Incorrect password'
        );
    }

    return new Right(['hello' => 'world']);
}

$prop = function ($k)
{
    return function ($xs) use ($k)
    {
        return isset ($xs[$k])
            ? new Right($xs[$k])
            : new Left('No such key.');
    };
};

$id = function ($x)
{
    return $x;
};

// Some examples...
$badUsername = $login('fur', 'bar')->chain($prop('id'));
$badPassword = $login('foo', 'bear')->chain($prop('id'));
$badKey = $login('foo', 'bar')->chain($prop('brian'));
$good = $login('foo', 'bar')->chain($prop('id'));

assert($badUsername->either($id, $id) === 'Invalid username');
assert($badPassword->either($id, $id) === 'Incorrect password');
assert($badKey->either($id, $id) === 'No such key.');
assert($good->either($id, $id) === 'world');

use PhpFp\Either\Either;

$id = function ($x) { return $x; };

assert(Either::of('test')->either($id, $id) == 'test');

use PhpFp\Either\Either;
use PhpFp\Either\Constructor\Left;

$either = Either::left('test');

assert($either instanceof Either);
assert($either instanceof Left);

use PhpFp\Either\Either;
use PhpFp\Either\Constructor\Right;

$either = Either::right('test');

assert($either instanceof Either);
assert($either instanceof Right);

use PhpFp\Either\Either;

$id = function ($x) { return $x; };

$f = function () { throw new \Exception; };
$g = function () { return 'hello'; };

assert(Either::tryCatch($f)->either($id, $id) instanceof \Exception);
assert(Either::tryCatch($g)->either($id, $id) === 'hello');

use PhpFp\Either\Constructor\{Left, Right};

$id = function ($x) { return $x; };

$addTwo = Either::of(
    function ($x)
    {
        return $x + 2;
    }
);

$a = new Right(5);
$b = new Left(4);

assert($addTwo->ap($a)->either($id , $id) === 7);
assert($addTwo->ap($b)->either($id, $id) === 4);

use PhpFp\Either\Constructor\{Left, Right};

$addOne = function ($x) { return $x + 1; };
$subOne = function ($x) { return $x - 1; };
$id = function ($x) { return $x; };

assert (Either::right(2)->bimap($addOne, $subOne)->either($id, $id) === 1);
assert (Either::left(2)->bimap($addOne, $subOne)->either($id, $id) === 3);

use PhpFp\Either\Constructor\{Left, Right};

$f = function ($x)
{
    return Either::of($x * 2);
}

$id = function ($x) { return $x; };

assert(Either::right(8)->chain($f)->either($id, $id) === 16);
assert(Either::left(8)->chain($f)->either($id, $id) === 8);

use PhpFp\Either\Constructor\{Left, Right};

$f = function ($x) { return $x - 5; };
$id = function ($x) { return $x; };

assert(Either::right(8)->map($f)->either($id, $id) === 3);
assert(Either::left(8)->map($f)->either($id, $id) === 8);

use PhpFp\Either\Constructor\{Left, Right};

$left = function ($x) { return (int) $x; };
$right = function ($x) { $x; };

assert(Either::left('7')->either($left, $right) === 7);
assert(Either::right(2)->either($left, $right) === 2);