Implement Symbol.toPrimitive

decimal.js

@@ -2467,6 +2467,14 @@
     return x.isNeg() ? '-' + str : str;
   };
 
+  /*
+   * The toPrimitive method is used when attempting to perform comparison operations.
+   * This implementation provides a sensible and user-expected implementation of how
+   * a Decimal should be transformed into a comparable number
+   */
+  P[Symbol.toPrimitive] = function () {
+    return Number(this.toString());
+  };
 
   // Helper functions for Decimal.prototype (P) and/or Decimal methods, and their callers.
 

test/modules/toPrimitive.js

@@ -0,0 +1,23 @@
+if (typeof T === 'undefined') require('../setup');
+
+T('Symbol.toPrimitive', function () {
+
+  function D(v) { return new Decimal(v); }
+
+  Decimal.config({
+    precision: 20,
+    rounding: 4,
+    toExpNeg: -9e15,
+    toExpPos: 9e15,
+    minE: -9e15,
+    maxE: 9e15
+  });
+
+  T.assert(D('1') < D('2'));
+  T.assert(D('100') > D('2'));
+  T.assert(D('-435435.232') < D('2.09802'));
+  T.assert(D('-1.987234') > D('-2.5473421'));
+  T.assert(D('10.3') >= D('10.3'));
+  T.assert(D('10.3') <= D('10.3'));
+});
+

test/test.js

@@ -64,7 +64,8 @@ console.log('\n Testing decimal.js\n');
   'toSD',
   'toString',
   'trunc',
-  'valueOf'
+  'valueOf',
+  'toPrimitive',
 ]
 .forEach(function (module) {
   require('./modules/' + module);