PHP version of imul

transcript

# this file is $a, $b, expected answer for imul($a, $b)
$ cat tests/imul.txt 
2,4,8
1,1,1
10,10,100
-1, -2, 2
1, 2, 2
-1, 2, -2
1, -2, -2
-0, 0, 0
0, -0, 0
-1, -0, 0
1, -0, 0
4294967295, 1, -1
4294967295, 4294967295, 1
4294967295, -4294967295, -1
4294967295, 4294967294, 2
4294967295, -4294967294, -2
65536, 65536, 0
 
# this checks that file in PHP and in Deno JS. JS gets them all right.
$ bash tests/run.sh
php failure: imul(4294967295, 4294967295) returned 1, should be 0
php failure: imul(4294967295, -4294967295) returned -1, should be 0
php failure: imul(4294967295, 4294967294) returned 2, should be 0
php failure: imul(4294967295, -4294967294) returned -2, should be 0
php imul successes: 13, failures: 4
js imul successes: 17, failures 0
 
$ cat test/test_maths.php
<?php
 
require(dirname(__FILE__) . "/../maths.php");
 
$imul = file_get_contents(dirname(__FILE__) . "/imul.txt");
$lines = explode("\n", $imul);
$successes = 0; $failures = 0;
foreach ($lines as $line) {
    $parts = explode(",", $line);
    if (count($parts) == 3) {
        $a = intval($parts[0]);
        $b = intval($parts[1]);
        $answer = intval($parts[2]);
        $try = imul($a, $b);
        if ($try == $answer) {
            $successes += 1;
        } else {
            $failures += 1;
            echo "php failure: imul($a, $b) returned $answer, should be $try\n";
        }
    }
}
echo("php imul successes: $successes, failures: $failures\n");
?>
 
$ cat test/maths.php
<?php
function imul($a, $b) {
    $c = ($a * $b) % (2**32);
    if ($c >= 2**31) $c -= 2**32;
    return $c;
}
?>