improve wrap function

src/util.rs

@@ -1,6 +1,6 @@
 #[inline]
 pub fn wrap(x: f32, max: f32) -> f32 {
-    x - max * ((x > max) as i32 as f32 - (x < 0.0_f32) as i32 as f32)
+    x - max * ((x > max) as i32 - x.is_sign_negative() as i32) as f32
 }
 
 /// Truncate x and y and return a corresponding index into the data slice.
@@ -18,7 +18,7 @@ mod test {
 
     #[test]
     fn wrap_test() {
-        assert_eq!(wrap(1.1, 1.0), 0.100000024);
+        assert_eq!(wrap(1.1, 1.0), 0.100000024); // floating point weirdness
         assert_eq!(wrap(0.5, 1.0), 0.5);
         assert_eq!(wrap(-1.0, 2.0), 1.0);
     }