Day: November 26, 2011

/**
*@function gcd (aka Euclid's algorithm)
*@purpose returns the greatest common factor between two numbers;
*/
function gcd(a, b) {
    return (b) ? gcd(b, a % b) : a;
}
/**
*@function dec2Frac
*@purpose returns a decimal as a fraction.
*/
var dec2Frac = function ( num ) {
	var top = num.toString().replace(/\d+[.]/, '');
	var bot = Math.pow(10, top.length);
	if (num > 1) {
		top = +top + Math.floor(num) * bot;
	}
	var x = gcd(top, bot);
	return (top / x) + "/" + (bot / x);
};

dec2Frac( 1.24325 ) // returns "4973/4000"
dec2Frac( 2.45 ) // returns "49/20"

//@requires Firebug or Chrome Developer Tools
//The following code test the speed difference between the Version 1 and 2 of dec2Frac.
function gcd(a, b) {
    return (b) ? gcd(b, a % b) : a;
}
var dec2FracV2 = function (d) {
	var top = d.toString().replace(/\d+[.]/, '');
	var bot = Math.pow(10, top.length);
	if (d > 1) {
		top = +top + Math.floor(d) * bot;
	}
	var x = gcd(top, bot);
	return (top / x) + "/" + (bot / x);
};
function dec2FracV1(d) {
    var df = 1, top = 1, bot = 1;
    var limit = 1e5; //Increase the limit to get more precision.
 
    while (df != d && limit-- > 0) {
        if (df < d) {
            top += 1;
        }
        else {
            bot += 1;
            top = parseInt(d * bot, 10);
        }
        df = top / bot;
    }
    return top + '/' + bot;
}
var getRandomNum = function (i, decLen) {
	return (Math.random() * (i || 1)).toFixed(decLen);
};
 
var runTest = function ( funcName ) {
	var func = { "V1": dec2FracV1, "V2": dec2FracV2 }[ funcName ];
	var i = 1000;
	while (i--) {
		num = getRandomNum(10, 4);
		var x = func(num);
		if (num != eval(x)) {
			console.warn("ERROR: Function %s, The fraction %s != %s", funcName, num, x);
		}
	}
};
console.time( 'V1' );
runTest( "V1" );
console.timeEnd( 'V1' );
 
console.time( 'V2' );
runTest( "V2" );
console.timeEnd( 'V2' );