PHP 7.0.6 Released

    gmp_com

    (PHP 4 >= 4.0.4, PHP 5, PHP 7)

    gmp_com — Calculates one's complement

    Description

    GMP gmp_com ( GMP $a )

    Returns the one's complement of a.

    Parameters

    a

    Either a GMP number resource in PHP 5.5 and earlier, a GMP object in PHP 5.6 and later, or a numeric string provided that it is possible to convert the latter to a number.

    Return Values

    Returns the one's complement of a, as a GMP number.

    Examples

    Example #1 gmp_com() example

    <?php
    $com     = gmp_com("1234");
    echo     gmp_strval($com) . "\n";
    ?>

    The above example will output:

    -1235

    User Contributed Notes

    xo at jdbartlett dot com
    6 years ago
    If you're using one's compliment (bitwise NOT) to flip all $a's bits, don't forget that you need to use a mask to specify how many bits you expect in your result:

    <?php gmp_and(gmp_com('1234'), '2047') ?>
    >> 813 // 01100101101 in binary

    I chose 2047 because 1234 is an 11-bit binary number and 2047 is the maximum an 11-bit register can hold:

    11111111111  (2047)
    10011010010  (1234)
    01100101101  (813)
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