gmp_hamdist

(PHP 4 >= 4.0.4, PHP 5)

gmp_hamdist — Hamming distance

Beskrivelse

int gmp_hamdist ( resource $a , resource $b )

Returns the hamming distance between a and b. Both operands should be non-negative.

Parametre

a

It can be either a GMP number resource, or a numeric string given that it is possible to convert the latter to a number.

It should be positive.

b

It can be either a GMP number resource, or a numeric string given that it is possible to convert the latter to a number.

It should be positive.

Returnerings Værdier

A GMP number resource.

Eksempler

Eksempel #1 gmp_hamdist() example


<?php
$ham1 = gmp_init("1001010011", 2);
$ham2 = gmp_init("1011111100", 2);
echo gmp_hamdist($ham1, $ham2) . "\n";

/* hamdist is equivilent to: */
echo gmp_popcount(gmp_xor($ham1, $ham2)) . "\n";
?>

The above example will output:

6
6

Se også

gmp_popcount() - Population count
gmp_xor() - Bitwise XOR

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User Contributed Notes 2 notes

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Bas Vijfwinkel ¶

6 years ago


For those without gmp support :

$hamming_distance = count(array_diff_assoc(str_split($string1), str_split($string2)));

And if you are not sure if your strings have equal length :

$hamming_distance = count(array_diff_assoc(str_split(str_pad($string1,strlen($string2)-strlen($string1),' ')), str_split(str_pad($string2,strlen($string1)-strlen($string2),' '))));

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grabzila at gmail dot com ¶

3 years ago


<?php
$hamdist = gmp_hamdist(-100, -10); // 4
$hamdist = gmp_hamdist(100, 10);  // 5
?>

The function works great with negative numbers.

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