Add cast method to Quaternion

src/quaternion.rs

@@ -18,7 +18,7 @@ use std::mem;
 use std::ops::*;
 
 use rand::{Rand, Rng};
-use num_traits::cast;
+use num_traits::{NumCast, cast};
 
 use structure::*;
 
@@ -229,6 +229,13 @@ impl<S: BaseFloat> MetricSpace for Quaternion<S> {
     }
 }
 
+impl<S: NumCast + Copy> Quaternion<S> {
+    /// Component-wise casting to another type.
+    pub fn cast<T: BaseFloat>(&self) -> Quaternion<T> {
+        Quaternion::from_sv(NumCast::from(self.s).unwrap(), self.v.cast())
+    }
+}
+
 #[cfg(not(feature = "simd"))]
 impl<S: BaseFloat> InnerSpace for Quaternion<S> {
     #[inline]

tests/quaternion.rs

@@ -331,3 +331,13 @@ mod rotate_between_vectors {
         assert_ulps_eq!(Quaternion::between_vectors(a, b), expected);
     }
 }
+
+mod cast {
+    use cgmath::*;
+
+    #[test]
+    fn test_cast() {
+        assert_ulps_eq!(Quaternion::new(0.9f64, 1.5, 2.4, 7.6).cast(),
+                        Quaternion::new(0.9f32, 1.5, 2.4, 7.6));
+    }
+}