PHP | gmp_hamdist() Function

The gmp_hamdist() is a built-in function in PHP which is used to find the hamming distance between two GMP numbers (GNU Multiple Precision : For large numbers).

Hamming distance between two numbers is defined as number of mis-matching bits in their binary representation.

Syntax:



gmp_hamdist ( $num1, $num2)

Parameters: This function accepts two GMP numbers $num1 and $num2 as shown in the above syntax. Both of these parameters are mandatory to be passed and must be positive. This function finds the hamming distance between the two numbers $num1 and $num2. These parameters can be a GMP object in PHP version 5.6 and later, or we are also allowed to pass a numeric string provided that it is possible to convert that string to a number.

Return Value: This function returns a GMP number which is the calculated hamming distance of the two numbers passed to it as arguments.

Examples:

Input:  $a = "3", $b = "11"
Output: 1
Explanation: Binary representation of 3 is 0011
Binary representation of 11 is 1011. So, they 
differ by only 1 bit.

Input:  $a = "4", $b = "4"
Output: 0

Below programs illustrate the gmp_hamdist() function in PHP :

Program 1: Program to calculate the hamming distance when numeric strings as GMP numbers are passed as arguments.

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<?php
// PHP program to calculate hamming distance
   
// strings as GMP numbers 
$a = "3";
$b = "11";
   
// calculates the hamming distance
$hamDist = gmp_hamdist($a, $b);
echo $hamDist."\n";
   
// calculates the hamming distance
$a = "4"; $b = "4";
$hamDist = gmp_hamdist($a, $b);
echo $hamDist."\n";
   
?>

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Output:

4
12

Program 2: Program to calculate the hamming distance when GMP numbers are passed as arguments.

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<?php
// PHP program to calculate hamming distance
   
// creating GMP numbers using gmp_init() 
$a = gmp_init("11", 2); // 3 in decimal
$b = gmp_init("1011", 2); // 11 in decimal
   
// calculates the hamming distance
$hamDist = gmp_hamdist($a, $b);
echo $hamDist."\n";
   
// calculates the hamming distance
$a = gmp_init("100", 2);
$b = gmp_init("100", 2);
$hamDist = gmp_hamdist($a, $b);
echo $hamDist."\n";
   
?>

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Output:

1
0

Reference:
http://php.net/manual/en/function.gmp-hamdist.php



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