Fractions

/**

 * Wrapped an open source fractional library for Servoy use.

 * Note: this is an early version of ratio.js. (https://github.com/LarryBattle/Ratio.js)

 * @author Data Mosaic <http://www.data-mosaic.com/>

 * 

 * @author Larry Battle <http://bateru.com/news/contact-me>

 * @license MIT

 * @version 1.0

 * @date May 08, 2012

 * @purpose To provide a function that converts a decimal to a simplified fraction.

 * @info <http://bateru.com/news/2012/05/code-of-the-day-javascript-convert-decimal-to-a-simplified-fraction/>

 */

/**

 * Highest denominator to attempt to match on

 * @type {Number}

 * @private 

 *

 * @properties={typeid:35,uuid:"D2D263FE-7078-410E-A130-5DC6427D39D2",variableType:4}

 */

var _fractionPrecision = 64;

/**

 * Highest number of decimals

 * @type {Number}

 * @private 

 *

 * @properties={typeid:35,uuid:"B3D8AC4E-18C4-42EF-A643-26B531D7F733",variableType:4}

 */

var _decimalPrecision = 6;

/**

 * Only calculate the fraction array once

 * @type {Object}

 * @private

 *

 * @properties={typeid:35,uuid:"DFCD9BB3-AFAF-4299-80F1-30A89B6EF19C",variableType:-4}

 */

var _fractionObject = getFractionObject();

/**

 * Get object with all possible fractions

 * @private  

 *

 * @properties={typeid:24,uuid:"74B39990-D0A6-44A6-A209-5E2823AF2380"}

 */

function getFractionObject() {

	function getKeys(obj) {

	 	var props = [];

		for (var prop in obj) {

			if (obj.hasOwnProperty(prop)) {

				props.push(prop);

			}

		}

		return props;

	};

	var obj = {

		0 : '0',

		1 : '1'

	},

	num = _fractionPrecision,

	den = _fractionPrecision + 1,

	value;

	while (--num) {

		while (--den > 1) {

			value = (num / den).toFixed(_decimalPrecision);

			if (value < 1) {

				obj[value] = num + "/" + den;

			}

		}

		den = _fractionPrecision + 1;

	}

	obj.keys = getKeys(obj);

	return obj;

};

/**

 * Get the closest number

 * 

 * @param {Number[]} arr

 * @param {Number} val

 * @return {Number|Boolean}

 * @private 

 *

 * @properties={typeid:24,uuid:"F76DF876-15E8-4AD3-949B-22E3C16602E4"}

 */

function getClosestNum(arr, val) {

	if (typeof arr !== "object" || !(arr.hasOwnProperty('length')) || isNaN(val)) {

		return false;

	}

	var i = arr.length,

	j = i - 1,

	minDiff = Math.abs(+val - arr[j]),

	diff;

	while (i--) {

		diff = Math.abs(+val - arr[i]);

		if (diff < minDiff) {

			minDiff = diff;

			j = i;

		}

	}

	return arr[j];

};

/**

 * Get a fraction representation from a decimal

 * 

 * @param {Number} dec

 * @return {String|Boolean}

 *

 * @properties={typeid:24,uuid:"9654BA30-4AA4-4C93-BCEF-108F4730E4E0"}

 */

function getFractionFromDecimal(dec) {

	if (isNaN(dec) || !isFinite(dec)) {

		return false;

	}

	if (!/\./.test(dec)) {

		return dec;

	}

	var fracs = _fractionObject,

	matches = dec.toString().match(/(\d+)(\.\d+)/),

	fraction = fracs[getClosestNum(fracs.keys, Math.abs(+matches[2]))],

	sign = ( 0 < dec || (fraction == "0" && Math.abs(dec) < 1) ) ? '' : '-';

	if (1 < Math.abs(dec)) {

		if (isNaN(fraction)) {

			fraction = +matches[1] + " " + fraction;

		} else {

			fraction = +matches[1] + (+fraction);

		}

	}

	return sign + fraction;

};

/**

 * Get a decimal representation from a fraction

 * 

 * @param {String} fraction

 * @return {Number|Boolean}

 *

 * @properties={typeid:24,uuid:"41703256-520A-42B4-84EC-D8813CE6DA77"}

 */

function getDecimalFromFraction(fraction) {

	var parts = [],

	j,

	arr = [];

	/**

	 * @param {Array} parts

	 * @param {Array} arr

	 * @return {Number}

	 */

	function frac(parts,arr) {

		function getNumeratorWithSign(top, bottom) {

			var sign = (+top * (+bottom || 1)) < 0 ? -1 : 1;

			return Math.abs(+top) * sign;

		}

		parts = parts.split(/\//);

		arr[0] = getNumeratorWithSign(parts[0], parts[1]);

		arr[1] = Math.abs(+parts[1]);

		return arr

	}

	//nothing

	if (!fraction) {

		return 0

	}

	//whole number

	else if (fraction == parseInt(fraction)) {

		return parseInt(fraction)

	}

	else if (/\d\s*\//.test(fraction)) {

		//mixed number

		if (/\d\s+[+\-]?\d/.test(fraction)) {

			parts = fraction.match(/(\S+)\s+(\S.*)/);

			arr = frac(parts[2],[]);

			j = 0 < (parseFloat(parts[1]) * arr[0]) ? 1 : -1;

			arr[0] = j * (Math.abs(arr[0]) + Math.abs(parts[1] * arr[1]));

		}

		//fraction

		else {

			arr = frac(fraction,arr)

		}

		return arr[0] / arr[1]

	}

}

/**

 * Called for performing a conversion between a displayed value and a database value.

 *

 * @param {String|Number} displayedValue The displayed value.

 *

 * @return {Number} the database value.

 *

 * @properties={typeid:24,uuid:"861CC360-A31D-48FC-991E-416A5A7C3941"}

 */

function convertFraction2DB(displayedValue) {

	if (typeof displayedValue == 'string') {

		return getDecimalFromFraction(displayedValue)

	}	

}

/**

 * Called for performing a conversion between a database value and a displayed value.

 *

 * @param {Number} databaseValue The database value.

 *

 * @return {String} the displayed value.

 *

 * @properties={typeid:24,uuid:"6F37C385-32FF-4B62-A54B-B4E82BF9A5FB"}

 */

function convertDB2Fraction(databaseValue) {

	//don't show .0 for whole numbers

	if (typeof databaseValue == 'number' && parseInt(databaseValue) == databaseValue) {

		return utils.numberFormat(databaseValue,'#')

	}

	//format the fraction

	else if (typeof databaseValue == 'number') {

		return getFractionFromDecimal(databaseValue)

	}

	//shouldn't need this return; needed to break out of loop when called with display instead of database value as input

	else {

		return databaseValue

	}

}