Merge pull request #11 from danielparks/float-like-int

Make float code work like int code.

src/lib.rs

@@ -154,23 +154,25 @@ macro_rules! roundable_float {
                 assert!(factor > 0.0, "try_round_to() requires positive factor");
 
                 let remainder = self % factor;
-                let remainder = if remainder < 0.0 {
-                    // Safe: remainder is negative so adding it to factor will
-                    // never overflow (|remainder| < factor).
-                    factor + remainder
-                } else {
-                    remainder
-                };
 
                 // Safe: remainder has the same sign as self, so subtracting
                 // remainder will always be closer to 0. Also, remainder is
                 // always between 0 and self, so it base can never switch signs.
                 let base = self - remainder;
 
-                if remainder < factor / 2.0 {
-                    Some(base)
+                #[allow(unused_comparisons)]
+                if self < 0.0 {
+                    if remainder < factor / 2.0 - factor {
+                        Some(base - factor)
+                    } else {
+                        Some(base)
+                    }
                 } else {
-                    Some(base + factor)
+                    if remainder < factor / 2.0 {
+                        Some(base)
+                    } else {
+                        Some(base + factor)
+                    }
                 }
             }
         }