// wink-distance
// Distance functions for Bag of Words, Strings,
// Vectors and more.
//
// Copyright (C) GRAYPE Systems Private Limited
//
// This file is part of “wink-distance”.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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// DEALINGS IN THE SOFTWARE.
// ## string
// ### hammingNormalized
/**
*
* Computes the normalized hamming distance between two strings. These strings
* may be of different lengths. Normalized distance is always between 0 and 1.
*
* @method string.hammingNormalized
* @param {string} str1 first string.
* @param {string} str2 second string.
* @return {number} normalized hamming distance between `str1` and `str2`.
* @example
* hammingNormalized( 'john', 'johny' );
* // -> 0.2
* hammingNormalized( 'sam', 'sam' );
* // -> 0
* hammingNormalized( 'sam', 'samuel' );
* // -> 0.5
* hammingNormalized( 'saturn', 'urn' );
* // -> 1
*/
var hammingNormalized = function ( str1, str2 ) {
// As we may need to swap values!
var s1 = str1,
s2 = str2;
// String lengths.
var s1Length = s1.length,
s2Length = s2.length;
// Absolute distance between `s1` & `s2`.
var distance;
// Helper variables.
var i, imax;
var dividend;
// Initialize stuff and may have to swap `s1`/`s2`.
if ( s1Length < s2Length ) {
// Swap `s1` and `s2` values.
s1 = [ s2, s2 = s1 ][ 0 ];
// Initialize distance as the difference in lengths of `s1` & `s2`.
distance = s2Length - s1Length;
imax = s1Length;
// Initialize dividend by the larger string length.
dividend = s2Length;
} else {
// No need to swap, but do initialize stuff.
distance = s1Length - s2Length;
imax = s2Length;
dividend = s1Length;
}
// Compute distance.
for ( i = 0; i < imax; i += 1 ) {
if ( s1[ i ] !== s2[ i ] ) distance += 1;
}
// Normalize the distance & return.
return ( dividend ) ? ( distance / dividend ) : 0;
}; // hammingNormalized()
module.exports = hammingNormalized;