implemented 6 more passing tests for range. Now works like python's range

underscore.js

@@ -33,19 +33,33 @@
   // Current version.
   _.VERSION = '0.4.5';
 
-  /*------------------------ Generator Functions: ----------------------------*/
-  _.range = function(upper, lower, step) {
-    if (!lower) var lower = 0;
-    if (!step) var step = 1;
+  /*------------------------ Generator Functions: ---------------------------*/
 
-    var result = new Array(((upper - lower) / step) + 1));
-
-    for (var i = lower; i <= upper; i += step) {
-        result[i] = i;
+  // Generates an Array, containing an arithmetic progressions
+  // Analog of python's built-in function 'range'
+  _.range = function(start, stop, step) {
+    if (!stop) {
+      var stop = start;
+      start = 0;
     }
 
-    return result;
-  }
+    if (!step) var step = 1;
+
+    var length = Math.ceil((stop - start) / step);
+
+    if (length < 0) {
+      return [];
+    }
+
+    var results = new Array(length);
+    var resIdx = 0;
+
+    for (var i = start; (start <= stop ? stop - i > 0 : i - stop > 0); i += step) {
+      results[resIdx++] = i;
+    }
+
+    return results;
+  };
 
   /*------------------------ Collection Functions: ---------------------------*/