Merge branch 'master' of https://github.com/trevnorris/d3 into v2.8.0

I simplified the implementation, though it still seems somewhat magical. I
would be more confident if there were an easy way to extract the mantissa and
exponent from a floating point number, but since JavaScript does not expose the
bitwise representation of numbers, there's no easy way to do it.

d3.js

@@ -391,11 +391,6 @@ function d3_splitter(d) {
 function d3_collapse(s) {
   return s.replace(/(^\s+)|(\s+$)/g, "").replace(/\s+/g, " ");
 }
-/**
- * @param {number} start
- * @param {number=} stop
- * @param {number=} step
- */
 d3.range = function(start, stop, step) {
   if (arguments.length < 3) {
     step = 1;
@@ -404,14 +399,22 @@ d3.range = function(start, stop, step) {
       start = 0;
     }
   }
-  if ((stop - start) / step == Infinity) throw new Error("infinite range");
+  if ((stop - start) / step === Infinity) throw new Error("infinite range");
   var range = [],
+       k = d3_range_integerScale(Math.abs(step)),
        i = -1,
        j;
-  if (step < 0) while ((j = start + step * ++i) > stop) range.push(j);
-  else while ((j = start + step * ++i) < stop) range.push(j);
+  start *= k, stop *= k, step *= k;
+  if (step < 0) while ((j = start + step * ++i) > stop) range.push(j / k);
+  else while ((j = start + step * ++i) < stop) range.push(j / k);
   return range;
 };
+
+function d3_range_integerScale(x) {
+  var k = 1;
+  while (x * k % 1) k *= 10;
+  return k;
+}
 d3.requote = function(s) {
   return s.replace(d3_requote_re, "\\$&");
 };

src/core/range.js

@@ -1,8 +1,3 @@
-/**
- * @param {number} start
- * @param {number=} stop
- * @param {number=} step
- */
 d3.range = function(start, stop, step) {
   if (arguments.length < 3) {
     step = 1;
@@ -11,11 +6,19 @@ d3.range = function(start, stop, step) {
       start = 0;
     }
   }
-  if ((stop - start) / step == Infinity) throw new Error("infinite range");
+  if ((stop - start) / step === Infinity) throw new Error("infinite range");
   var range = [],
+       k = d3_range_integerScale(Math.abs(step)),
        i = -1,
        j;
-  if (step < 0) while ((j = start + step * ++i) > stop) range.push(j);
-  else while ((j = start + step * ++i) < stop) range.push(j);
+  start *= k, stop *= k, step *= k;
+  if (step < 0) while ((j = start + step * ++i) > stop) range.push(j / k);
+  else while ((j = start + step * ++i) < stop) range.push(j / k);
   return range;
 };
+
+function d3_range_integerScale(x) {
+  var k = 1;
+  while (x * k % 1) k *= 10;
+  return k;
+}

test/core/range-test.js

@@ -36,6 +36,16 @@ suite.addBatch({
       assert.deepEqual(range(5, 8.5, .5), [5, 5.5, 6, 6.5, 7, 7.5, 8]);
       assert.deepEqual(range(2, 0, -.5), [2, 1.5, 1, .5]);
     },
+    "handles fractional steps without rounding errors": function(range) {
+      assert.deepEqual(range(0, 0.5, 0.1), [0, 0.1, 0.2, 0.3, 0.4]);
+      assert.deepEqual(range(-2, -1.2, 0.1), [-2, -1.9, -1.8, -1.7, -1.6, -1.5, -1.4, -1.3]);
+    },
+    "handles extremely small steps without rounding errors": function(range) {
+      assert.deepEqual(range(2.1e-31, 5e-31, 1.1e-31), [2.1e-31, 3.2e-31, 4.3e-31]);
+    },
+    "handles extremely large steps without rounding errors": function(range) {
+      assert.deepEqual(range(1e300, 2e300, 0.3e300), [1e300, 1.3e300, 1.6e300, 1.9e300]);
+    },
     "returns an ascending range if step is positive": function(range) {
       assert.deepEqual(range(0, 5, 1), [0, 1, 2, 3, 4]);
     },