Allow 0 to be passed without unit

This commit finish fixing issue #552. It makes it unnecessary to specify a
unit with 0 when interacting with another SVG.Number that has a unit.

This was accomplished by modifying the operation methods of SVG.Number to
allow them to use the unit of the passed number when this number as no unit.

1 files changed, 8 insertions, 4 deletions

diff --git a/src/number.js b/src/number.js
index d0ccf4e..8198e7c 100644
--- a/src/number.js
+++ b/src/number.js
@@ -57,19 +57,23 @@ SVG.Number = SVG.invent({
     }
     // Add number
   , plus: function(number) {
-      return new SVG.Number(this + new SVG.Number(number), this.unit)
+      number = new SVG.Number(number)
+      return new SVG.Number(this + number, this.unit || number.unit)
     }
     // Subtract number
   , minus: function(number) {
-      return this.plus(-new SVG.Number(number))
+      number = new SVG.Number(number)
+      return new SVG.Number(this - number, this.unit || number.unit)
     }
     // Multiply number
   , times: function(number) {
-      return new SVG.Number(this * new SVG.Number(number), this.unit)
+      number = new SVG.Number(number)
+      return new SVG.Number(this * number, this.unit || number.unit)
     }
     // Divide number
   , divide: function(number) {
-      return new SVG.Number(this / new SVG.Number(number), this.unit)
+      number = new SVG.Number(number)
+      return new SVG.Number(this / number, this.unit || number.unit)
     }
     // Convert to different unit
   , to: function(unit) {