Fix d3/d3-scale#113.

Author: mbostock

src/ticks.js

@@ -3,14 +3,15 @@ var e10 = Math.sqrt(50),
     e2 = Math.sqrt(2);
 
 export default function(start, stop, count) {
-  var reverse = stop < start,
+  var reverse,
       i = -1,
       n,
       ticks,
       step;
 
-  if (reverse) n = start, start = stop, stop = n;
-
+  stop = +stop, start = +start, count = +count;
+  if (start === stop && count > 0) return [start];
+  if (reverse = stop < start) n = start, start = stop, stop = n;
   if ((step = tickIncrement(start, stop, count)) === 0 || !isFinite(step)) return [];
 
   if (step > 0) {

test/ticks-test.js

@@ -12,12 +12,16 @@ tape("ticks(start, stop, count) returns the empty array if any argument is NaN",
   test.end();
 });
 
-tape("ticks(start, stop, count) returns the empty array if start === stop", function(test) {
+tape("ticks(start, stop, count) returns the empty array if start === stop and count is non-positive", function(test) {
   test.deepEqual(array.ticks(1, 1, -1), []);
   test.deepEqual(array.ticks(1, 1, 0), []);
   test.deepEqual(array.ticks(1, 1, NaN), []);
-  test.deepEqual(array.ticks(1, 1, 1), []);
-  test.deepEqual(array.ticks(1, 1, 10), []);
+  test.end();
+});
+
+tape("ticks(start, stop, count) returns the empty array if start === stop and count is positive", function(test) {
+  test.deepEqual(array.ticks(1, 1, 1), [1]);
+  test.deepEqual(array.ticks(1, 1, 10), [1]);
   test.end();
 });