Implement NumCast for NotNaN

Author: f-fr

src/lib.rs

@@ -15,7 +15,8 @@ use std::fmt;
 use std::io;
 use std::mem;
 use unreachable::unreachable;
-use num_traits::{Bounded, Float, FromPrimitive, Num, One, Signed, ToPrimitive, Zero};
+use num_traits::{Bounded, Float, FromPrimitive, Num, NumCast, One, Signed, ToPrimitive,
+                 Zero};
 
 /// A wrapper around Floats providing an implementation of Ord and Hash.
 ///
@@ -664,6 +665,12 @@ impl<T: Float + Signed> Signed for NotNaN<T> {
     fn is_negative(&self) -> bool { self.0.is_negative() }
 }
 
+impl<T: Float + NumCast> NumCast for NotNaN<T> {
+    fn from<F: ToPrimitive>(n: F) -> Option<Self> {
+        T::from(n).and_then(|n| NotNaN::new(n).ok())
+    }
+}
+
 #[cfg(feature = "serde")]
 mod impl_serde {
     extern crate serde;

tests/test.rs

@@ -168,6 +168,11 @@ describe! not_nan32 {
         assert_eq!(NotNaN::from(50f32).abs_sub(&NotNaN::from(8f32)), NotNaN::from(42f32));
         assert_eq!(NotNaN::from(8f32).abs_sub(&NotNaN::from(50f32)), NotNaN::from(0f32));
     }
+
+    it "should implement NumCast" {
+        assert_eq!(<NotNaN<f32> as num_traits::NumCast>::from(42), Some(NotNaN::from(42f32)));
+        assert_eq!(<NotNaN<f32> as num_traits::NumCast>::from(f32::nan()), None);
+    }
 }
 
 describe! not_nan64 {
@@ -295,6 +300,11 @@ describe! not_nan64 {
         assert_eq!(NotNaN::from(50f64).abs_sub(&NotNaN::from(8f64)), NotNaN::from(42f64));
         assert_eq!(NotNaN::from(8f64).abs_sub(&NotNaN::from(50f64)), NotNaN::from(0f64));
     }
+
+    it "should implement NumCast" {
+        assert_eq!(<NotNaN<f64> as num_traits::NumCast>::from(42), Some(NotNaN::from(42f64)));
+        assert_eq!(<NotNaN<f64> as num_traits::NumCast>::from(f64::nan()), None);
+    }
 }
 
 describe! hashing {