Added splitUnit function

lib/type/unit/Unit.js

@@ -11,6 +11,7 @@ function factory (type, config, load, typed, math) {
   var divide    = load(require('../../function/arithmetic/divideScalar'));
   var pow       = load(require('../../function/arithmetic/pow'));
   var abs       = load(require('../../function/arithmetic/abs'));
+  var fix       = load(require('../../function/arithmetic/fix'));
   var equal     = load(require('../../function/relational/equal'));
   var isNumeric = load(require('../../function/utils/isNumeric'));
   var format    = load(require('../../function/string/format'));
@@ -856,7 +857,12 @@ function factory (type, config, load, typed, math) {
    * @return {number | BigNumber | Fraction} Returns the unit value
    */
   Unit.prototype.toNumeric = function (valuelessUnit) {
-    var other = this.to(valuelessUnit);
+    var other = this;
+    if(valuelessUnit) {
+      // Allow getting the numeric value without converting to a different unit
+      other = this.to(valuelessUnit);
+    }
+
     if(other._isDerived()) {
       return other._denormalize(other.value);
     }
@@ -1165,6 +1171,37 @@ function factory (type, config, load, typed, math) {
     return bestPrefix;
   };
 
+  /**
+   * Returns an array of units whose sum is equal to this unit
+   * @memberof Unit
+   * @param {Array} [parts] An array of strings or valueless units. 
+   *
+   *   Example:
+   *
+   *   var u = new Unit(1, 'm');
+   *   u.splitUnit(['feet', 'inch']);
+   *     [ 3 feet, 3.3700787401575 inch ]
+   *
+   * @return {Array} An array of units.
+   */
+  Unit.prototype.splitUnit = function(parts) {
+
+    var x = this.clone();
+    var ret = [];
+    for(var i=0; i<parts.length; i++) {
+      x = x.to(parts[i]);
+      if(i==parts.length-1) break;
+      // fix rounds a number towards 0
+      var fixedVal = fix(x.toNumeric());
+      var y = new Unit(fixedVal, parts[i].toString());
+      ret.push(y);
+      x = subtract(x, y);
+    }
+    ret.push(x);
+
+    return ret;
+  };
+
   var PREFIXES = {
     NONE: {
       '': {name: '', value: 1, scientific: true}

lib/type/unit/index.js

@@ -8,6 +8,9 @@ module.exports = [
   // create new units
   require('./function/createUnit'),
 
+  // split units
+  require('./function/splitUnit'),
+
   // physical constants
   require('./physicalConstants')
 ];