From d2f605de23f950d0c5aef07f540bf686b1ebf4ee Mon Sep 17 00:00:00 2001
From: josdejong <wjosdejong@gmail.com>
Date: Sat, 16 Mar 2013 12:54:05 +0100
Subject: [PATCH] Fixed determining correct prefix for negative units

---
 src/type/Unit.js  |  7 +++----
 test/type/unit.js | 11 ++++++++++-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/type/Unit.js b/src/type/Unit.js
index 0b02c9f89..47d8d8e62 100644
--- a/src/type/Unit.js
+++ b/src/type/Unit.js
@@ -372,10 +372,10 @@ Unit.prototype.toString = function() {
         // the absolute value of the log10 is closest to zero,
         // though with a little offset of 1.2 for nicer values: you get a
         // sequence 1mm 100mm 500mm 0.6m 1m 10m 100m 500m 0.6km 1km ...
+        var absValue = Math.abs(this.value / this.unit.value);
         var bestPrefix = Unit.PREFIX_NONE;
         var bestDiff = Math.abs(
-            Math.log(this.value / this.unit.value / bestPrefix.value) /
-                Math.LN10 - 1.2);
+            Math.log(absValue / bestPrefix.value) / Math.LN10 - 1.2);
 
         var prefixes = this.unit.prefixes;
         for (var p in prefixes) {
@@ -383,8 +383,7 @@ Unit.prototype.toString = function() {
                 var prefix = prefixes[p];
                 if (prefix.scientific) {
                     var diff = Math.abs(
-                        Math.log(this.value / this.unit.value / prefix.value) /
-                            Math.LN10 - 1.2);
+                        Math.log(absValue / prefix.value) / Math.LN10 - 1.2);
 
                     if (diff < bestDiff) {
                         bestPrefix = prefix;
diff --git a/test/type/unit.js b/test/type/unit.js
index d70bca5f0..2ad99e981 100644
--- a/test/type/unit.js
+++ b/test/type/unit.js
@@ -7,7 +7,16 @@ var math = require('../../math.js'),
 
 
 var unit1 = new Unit(5000, 'cm');
-assert.equal(unit1, '50 m');
+assert.equal(unit1.toString(), '50 m');
+assert.equal(new Unit(5, 'kg').toString(), '5 kg');
+assert.equal(new Unit('5kg').toString(), '5 kg');
+assert.equal(new Unit('5 kg').toString(), '5 kg');
+assert.equal(new Unit(' 5 kg ').toString(), '5 kg');
+assert.equal(new Unit('5e-3kg').toString(), '5 g');
+assert.equal(new Unit('5e+3kg').toString(), '5 Mg');
+assert.equal(new Unit('-5kg').toString(), '-5 kg');
+assert.equal(new Unit('-5mg').toString(), '-5 mg');
+assert.equal(new Unit(null, 'kg').toString(), '1 kg');
 
 assert.throws(function () {
     Unit(2, 'inch');