Add trait for accessing the pointer to the first element of a type

src/cgmath/lib.rs

@@ -44,3 +44,5 @@ pub mod frustum;
 pub mod intersect;
 pub mod obb;
 pub mod sphere;
+
+pub mod ptr;

src/cgmath/ptr.rs

@@ -0,0 +1,38 @@
+// Copyright 2013 The CGMath Developers. For a full listing of the authors,
+// refer to the AUTHORS file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use array::Array;
+use matrix::{Mat2, Mat3, Mat4};
+use point::{Point2, Point3};
+use vector::{Vec2, Vec3, Vec4};
+
+pub trait Ptr<T> {
+    fn ptr<'a>(&'a self) -> &'a T;
+}
+
+impl<S: Clone> Ptr<S> for Vec2<S> { #[inline] fn ptr<'a>(&'a self) -> &'a S { self.i(0) } }
+impl<S: Clone> Ptr<S> for Vec3<S> { #[inline] fn ptr<'a>(&'a self) -> &'a S { self.i(0) } }
+impl<S: Clone> Ptr<S> for Vec4<S> { #[inline] fn ptr<'a>(&'a self) -> &'a S { self.i(0) } }
+
+impl<S: Clone> Ptr<S> for Point2<S> { #[inline] fn ptr<'a>(&'a self) -> &'a S { self.i(0) } }
+impl<S: Clone> Ptr<S> for Point3<S> { #[inline] fn ptr<'a>(&'a self) -> &'a S { self.i(0) } }
+
+impl<S: Clone> Ptr<S> for Mat2<S> { #[inline] fn ptr<'a>(&'a self) -> &'a S { self.i(0).i(0) } }
+impl<S: Clone> Ptr<S> for Mat3<S> { #[inline] fn ptr<'a>(&'a self) -> &'a S { self.i(0).i(0) } }
+impl<S: Clone> Ptr<S> for Mat4<S> { #[inline] fn ptr<'a>(&'a self) -> &'a S { self.i(0).i(0) } }
+
+impl<'self, T, P: Ptr<T>> Ptr<T> for &'self [P] {
+    #[inline] fn ptr<'a>(&'a self) -> &'a T { self[0].ptr() }
+}