From 51b3d2d4773574793427e24f1b69a92a95392dae Mon Sep 17 00:00:00 2001
From: Owen Sanchez <pengowen816@gmail.com>
Date: Thu, 13 Jul 2017 12:24:30 -0700
Subject: [PATCH] Add cast method to Quaternion

---
 src/quaternion.rs   |  9 ++++++++-
 tests/quaternion.rs | 10 ++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/quaternion.rs b/src/quaternion.rs
index 599756d..b3edec5 100644
--- a/src/quaternion.rs
+++ b/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]
diff --git a/tests/quaternion.rs b/tests/quaternion.rs
index 89bd531..315c5f3 100644
--- a/tests/quaternion.rs
+++ b/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));
+    }
+}