Type-cast a vector component-wise

This allows one to e.g. cast a vector of f64s to an equivalent vector of f32s.
More generally this is allowed for arbitrary NumCast types.

src/vector.rs

@@ -98,6 +98,7 @@
 
 use std::fmt;
 use std::mem;
+use std::num::NumCast;
 
 use angle::{Rad, atan2, acos};
 use approx::ApproxEq;
@@ -208,6 +209,14 @@ macro_rules! vec(
             fn one() -> $Self<$S> { $Self { $($field: one()),+ } }
         }
 
+        impl<$S: NumCast + Copy> $Self<$S> {
+            /// Component-wise casting to another type
+            #[inline]
+            pub fn cast<T: NumCast>(&self) -> $Self<T> {
+                $Self { $($field: NumCast::from(self.$field).unwrap()),+ }
+            }
+        }
+
         impl<$S> FixedArray<[$S, ..$n]> for $Self<$S> {
             #[inline]
             fn into_fixed(self) -> [$S, ..$n] {

tests/vector.rs

@@ -14,7 +14,10 @@
 // limitations under the License.
 
 #![feature(globs)]
+#![feature(phase)]
 
+#[phase(plugin)]
+extern crate cgmath;
 extern crate cgmath;
 
 use cgmath::*;
@@ -166,3 +169,10 @@ fn test_map() {
     assert_eq!(Vector3::new(7.12f64, 3.8f64, -6.98f64).map(|x| x.floor()), Vector3::new(7.0f64, 3.0f64, -7.0f64));
     assert_eq!(Vector3::new(7.12f64, 3.8f64, -6.98f64).map(|x| x.max(0.0f64)), Vector3::new(7.12f64, 3.8f64, 0.0f64));
 }
+
+#[test]
+fn test_cast() {
+    assert_approx_eq!(Vector2::new(0.9f64, 1.5).cast(), Vector2::new(0.9f32, 1.5));
+    assert_approx_eq!(Vector3::new(1.0f64, 2.4, -3.13).cast(), Vector3::new(1.0f32, 2.4, -3.13));
+    assert_approx_eq!(Vector4::new(13.5f64, -4.6, -8.3, 2.41).cast(), Vector4::new(13.5f32, -4.6, -8.3, 2.41));
+}