Merge pull request #230 from fawcilize/master

Adding a sum function to add variable-length arrays

src/functions.js

@@ -342,3 +342,13 @@ export function log1p(x) {
 export function log2(x) {
   return Math.log(x) / Math.LN2;
 }
+
+export function sum(array) {
+  if (!Array.isArray(array)) {
+    throw new Error('Sum argument is not an array');
+  }
+
+  return array.reduce(function (total, value) {
+    return total + Number(value);
+  }, 0);
+}

src/parser.js

@@ -48,7 +48,8 @@ import {
   cbrt,
   expm1,
   log1p,
-  log2
+  log2,
+  sum
 } from './functions';
 
 export function Parser(options) {
@@ -130,7 +131,8 @@ export function Parser(options) {
     fold: arrayFold,
     filter: arrayFilter,
     indexOf: stringOrArrayIndexOf,
-    join: arrayJoin
+    join: arrayJoin,
+    sum: sum
   };
 
   this.consts = {

test/functions.js

@@ -463,4 +463,26 @@ describe('Functions', function () {
       assert.strictEqual(parser.evaluate('join("", [1, 2, 3])'), '123');
     });
   });
+
+  describe('sum(array)', function () {
+    it('should fail if the argument is not an array', function () {
+      var parser = new Parser();
+      assert.throws(function () { parser.evaluate('sum(1)'); }, /not an array/);
+    });
+
+    it('should return zero with an empty array', function () {
+      var parser = new Parser();
+      assert.strictEqual(parser.evaluate('sum([])'), 0);
+    });
+
+    it('should work on a single-element array', function () {
+      var parser = new Parser();
+      assert.strictEqual(parser.evaluate('sum([1])'), 1);
+    });
+
+    it('should work on a multi-element array', function () {
+      var parser = new Parser();
+      assert.strictEqual(parser.evaluate('sum([1, 2])'), 3);
+    });
+  });
 });