Fixed in mod for negative numerators. Added more input validation. Added tests

HISTORY.md

@@ -14,7 +14,8 @@ https://github.com/josdejong/mathjs
 - Moved the parse code from prototype math.expr.Parser to function math.parse,
   simplified Parser a little bit.
 - Strongly simplified the code of Scope and Workspace.
-- Minor bug fixes.
+- Fixed function mod for negative numerators, and added error messages in case
+  of wrong input.
 
 
 ## 2013-05-18, version 0.8.2

README.md

@@ -723,6 +723,7 @@ Version 2.0:
 - A basic set of functions covering all common mathematical areas.
 - Functions and data types for numeral systems: Bin, Oct, Hex, Dec.
 - Arbitrary precision calculations with a BigNumber data type.
+- Support for derived units (like km/h, kg*m/s2, etc).
 
 
 ## License

math.js

@@ -7,7 +7,7 @@
  * mathematical functions, and a flexible expression parser.
  *
  * @version 0.8.3-SNAPSHOT
- * @date    2013-05-27
+ * @date    2013-05-29
  *
  * @license
  * Copyright (C) 2013 Jos de Jong <wjosdejong@gmail.com>
@@ -5409,28 +5409,14 @@ math.mod = function mod(x, y) {
         throw newArgumentsError('mod', arguments.length, 2);
     }
 
-    // TODO: only handle integer values in mod?
-    if (isNumber(x)) {
-        if (isNumber(y)) {
-            // number % number
-            return x % y;
-        }
-        else if (y instanceof Complex && y.im == 0) {
-            // number % complex
-            return x % y.re;
-        }
-    }
-    else if (x instanceof Complex && x.im == 0) {
-        if (isNumber(y)) {
-            // complex * number
-            return x.re % y;
-        }
-        else if (y instanceof Complex && y.im == 0) {
-            // complex * complex
-            return x.re % y.re;
-        }
+    // see http://functions.wolfram.com/IntegerFunctions/Mod/
+
+    if (isNumber(x) && isNumber(y)) {
+        // number % number
+        return _mod(x, y);
     }
 
+    // TODO: implement mod for complex values
 
     if (x instanceof Array || x instanceof Matrix ||
         y instanceof Array || y instanceof Matrix) {
@@ -5445,6 +5431,33 @@ math.mod = function mod(x, y) {
     throw newUnsupportedTypeError('mod', x, y);
 };
 
+/**
+ * Calculate the modulus of two numbers
+ * @param {Number} x
+ * @param {Number} y
+ * @returns {number} res
+ * @private
+ */
+function _mod(x, y) {
+    if (y > 0) {
+        if (x > 0) {
+            return x % y;
+        }
+        else if (x == 0) {
+            return 0;
+        }
+        else { // x < 0
+            return x - y * Math.floor(x / y);
+        }
+    }
+    else if (y == 0) {
+        return x;
+    }
+    else { // y < 0
+        // TODO: implement mod for a negative divisor
+        throw new Error('Cannot calculate mod for a negative divisor');
+    }
+}
 /**
  * Multiply two values.
  *

src/function/arithmetic/mod.js

@@ -15,28 +15,14 @@ math.mod = function mod(x, y) {
         throw newArgumentsError('mod', arguments.length, 2);
     }
 
-    // TODO: only handle integer values in mod?
-    if (isNumber(x)) {
-        if (isNumber(y)) {
-            // number % number
-            return x % y;
-        }
-        else if (y instanceof Complex && y.im == 0) {
-            // number % complex
-            return x % y.re;
-        }
-    }
-    else if (x instanceof Complex && x.im == 0) {
-        if (isNumber(y)) {
-            // complex * number
-            return x.re % y;
-        }
-        else if (y instanceof Complex && y.im == 0) {
-            // complex * complex
-            return x.re % y.re;
-        }
+    // see http://functions.wolfram.com/IntegerFunctions/Mod/
+
+    if (isNumber(x) && isNumber(y)) {
+        // number % number
+        return _mod(x, y);
     }
 
+    // TODO: implement mod for complex values
 
     if (x instanceof Array || x instanceof Matrix ||
         y instanceof Array || y instanceof Matrix) {
@@ -50,3 +36,31 @@ math.mod = function mod(x, y) {
 
     throw newUnsupportedTypeError('mod', x, y);
 };
+
+/**
+ * Calculate the modulus of two numbers
+ * @param {Number} x
+ * @param {Number} y
+ * @returns {number} res
+ * @private
+ */
+function _mod(x, y) {
+    if (y > 0) {
+        if (x > 0) {
+            return x % y;
+        }
+        else if (x == 0) {
+            return 0;
+        }
+        else { // x < 0
+            return x - y * Math.floor(x / y);
+        }
+    }
+    else if (y == 0) {
+        return x;
+    }
+    else { // y < 0
+        // TODO: implement mod for a negative divisor
+        throw new Error('Cannot calculate mod for a negative divisor');
+    }
+}

test/function/arithmetic/mod.js

@@ -1,2 +1,39 @@
+// test mod
+var assert = require('assert'),
+    approx = require('../../../tools/approx.js'),
+    math = require('../../../math.js'),
+    matrix = math.matrix,
+    range = math.range,
+    mod = math.mod;
 
-// TODO: test mod
+// test parser
+approx.equal(math.eval('8 % 3'), 2);
+approx.equal(math.eval('mod(8, 3)'), 2);
+
+// test number
+approx.equal(mod(7, 2), 1);
+approx.equal(mod(9, 3), 0);
+approx.equal(mod(10, 4), 2);
+assert.throws(function () {mod(10, -4)});
+approx.equal(mod(-10, 4), 2);
+assert.throws(function () {mod(-10, -4)});
+approx.equal(mod(8.2, 3), 2.2);
+approx.equal(mod(4, 1.5), 1);
+approx.equal(mod(0, 3), 0);
+
+// test wrong number of arguments
+assert.throws(function () {mod(1)}, SyntaxError);
+assert.throws(function () {mod(1,2,3)}, SyntaxError);
+
+// test complex
+assert.throws(function () {mod(math.complex(1,2), 3)}, TypeError);
+assert.throws(function () {mod(3, math.complex(1,2))}, TypeError);
+
+// test string
+assert.throws(function () {mod('string', 3)}, TypeError);
+assert.throws(function () {mod(5, 'string')}, TypeError);
+
+// test array, matrix, range
+approx.deepEqual(mod([-4,-3,-2,-1,0,1,2,3,4], 3), [2,0,1,2,0,1,2,0,1]);
+approx.deepEqual(mod(matrix([-4,-3,-2,-1,0,1,2,3,4]), 3), matrix([2,0,1,2,0,1,2,0,1]));
+approx.deepEqual(mod(range(-4,4), 3), [2,0,1,2,0,1,2,0,1]);

test/function/utils/subset.js

@@ -1,4 +1,4 @@
-// TODO: test subset
+// test subset
 var assert = require('assert'),
     math = require('../../../math.js'),
     subset = math.subset,
@@ -128,7 +128,7 @@ assert.deepEqual(parser.eval('a(:,2)'), matrix([[2],[4]]));
 assert.deepEqual(parser.eval('a(:,2) = [-2;-4]'), matrix([[1,-2],[3,-4]]));
 assert.deepEqual(parser.eval('b=123'), 123);
 assert.deepEqual(parser.eval('b(1)'), 123);
-// assert.deepEqual(parser.eval('b(1,1)'), 123); // TODO: should be supported
+// assert.deepEqual(parser.eval('b(1,1)'), 123); // TODO: should be supported?
 assert.deepEqual(parser.eval('b(1)=456'), 456);
 assert.deepEqual(parser.eval('b'), 456);
 assert.deepEqual(parser.eval('c="hello"'), "hello");