Merge #122

122: NAN preserving clamp_lower/upper r=cuviper a=termoshtt

`NAN` preserving lower- and upper-clamp.

Cc: https://github.com/rust-ndarray/ndarray/issues/470#issuecomment-521809782

Co-authored-by: Toshiki Teramura <toshiki.teramura@gmail.com>

src/lib.rs

@@ -376,17 +376,56 @@ pub fn clamp<T: PartialOrd>(input: T, min: T, max: T) -> T {
     }
 }
 
+/// A value bounded by a minimum value
+///
+///  If input is less than min then this returns min.
+///  Otherwise this returns input.
+///  `clamp_min(std::f32::NAN, 1.0)` preserves `NAN` different from `f32::min(std::f32::NAN, 1.0)`.
+#[inline]
+pub fn clamp_min<T: PartialOrd>(input: T, min: T) -> T {
+    if input < min {
+        min
+    } else {
+        input
+    }
+}
+
+/// A value bounded by a maximum value
+///
+///  If input is greater than max then this returns max.
+///  Otherwise this returns input.
+///  `clamp_max(std::f32::NAN, 1.0)` preserves `NAN` different from `f32::max(std::f32::NAN, 1.0)`.
+#[inline]
+pub fn clamp_max<T: PartialOrd>(input: T, max: T) -> T {
+    if input > max {
+        max
+    } else {
+        input
+    }
+}
+
 #[test]
 fn clamp_test() {
     // Int test
     assert_eq!(1, clamp(1, -1, 2));
     assert_eq!(-1, clamp(-2, -1, 2));
     assert_eq!(2, clamp(3, -1, 2));
+    assert_eq!(1, clamp_min(1, -1));
+    assert_eq!(-1, clamp_min(-2, -1));
+    assert_eq!(-1, clamp_max(1, -1));
+    assert_eq!(-2, clamp_max(-2, -1));
 
     // Float test
     assert_eq!(1.0, clamp(1.0, -1.0, 2.0));
     assert_eq!(-1.0, clamp(-2.0, -1.0, 2.0));
     assert_eq!(2.0, clamp(3.0, -1.0, 2.0));
+    assert_eq!(1.0, clamp_min(1.0, -1.0));
+    assert_eq!(-1.0, clamp_min(-2.0, -1.0));
+    assert_eq!(-1.0, clamp_max(1.0, -1.0));
+    assert_eq!(-2.0, clamp_max(-2.0, -1.0));
+    assert!(clamp(::core::f32::NAN, -1.0, 1.0).is_nan());
+    assert!(clamp_min(::core::f32::NAN, 1.0).is_nan());
+    assert!(clamp_max(::core::f32::NAN, 1.0).is_nan());
 }
 
 #[test]