Add and `Identity` matrix type.

It implements most matrix traits but all its operations are no-ops.

src/identity_spec.rs

@@ -0,0 +1,157 @@
+use std::num::{One, Zero};
+use mat;
+use traits::inv::Inv;
+use traits::transpose::Transpose;
+use traits::rlmul::{RMul, LMul};
+use traits::translation::{Translation, Translate};
+use traits::rotation::{Rotation, Rotate};
+use traits::transformation::{Transformation, Transform};
+
+impl One for mat::Identity {
+    #[inline]
+    fn one() -> mat::Identity {
+        mat::Identity
+    }
+}
+
+impl Inv for mat::Identity {
+    fn inverse(&self) -> Option<mat::Identity> {
+        Some(mat::Identity)
+    }
+
+    fn inplace_inverse(&mut self) -> bool {
+        true
+    }
+}
+
+impl<M: Clone> RMul<M> for mat::Identity {
+    fn rmul(&self, m: &M) -> M {
+        m.clone()
+    }
+}
+
+impl<M: Clone> LMul<M> for mat::Identity {
+    fn lmul(&self, m: &M) -> M {
+        m.clone()
+    }
+}
+
+impl<M: Clone> Mul<M, M> for mat::Identity {
+    #[inline]
+    fn mul(&self, other: &M) -> M {
+        other.clone()
+    }
+}
+
+impl Transpose for mat::Identity {
+    #[inline]
+    fn transposed(&self) -> mat::Identity {
+        mat::Identity
+    }
+
+    #[inline]
+    fn transpose(&mut self) {
+    }
+}
+
+impl<V: Zero> Translation<V> for mat::Identity {
+    #[inline]
+    fn translation(&self) -> V {
+        Zero::zero()
+    }
+
+    #[inline]
+    fn inv_translation(&self) -> V {
+        Zero::zero()
+    }
+
+    #[inline]
+    fn translate_by(&mut self, _: &V) {
+        fail!("Attempted to translate the identity matrix.")
+    }
+
+    #[inline]
+    fn translated(&self, _: &V) -> mat::Identity {
+        fail!("Attempted to translate the identity matrix.")
+    }
+}
+
+impl<V: Clone> Translate<V> for mat::Identity {
+    #[inline]
+    fn translate(&self, v: &V) -> V {
+        v.clone()
+    }
+
+    #[inline]
+    fn inv_translate(&self, v: &V) -> V {
+        v.clone()
+    }
+}
+
+impl<V: Zero> Rotation<V> for mat::Identity {
+    #[inline]
+    fn rotation(&self) -> V {
+        Zero::zero()
+    }
+
+    #[inline]
+    fn inv_rotation(&self) -> V {
+        Zero::zero()
+    }
+
+    #[inline]
+    fn rotate_by(&mut self, _: &V) {
+        fail!("Attempted to rotate the identity matrix.")
+    }
+
+    #[inline]
+    fn rotated(&self, _: &V) -> mat::Identity {
+        fail!("Attempted to rotate the identity matrix.")
+    }
+}
+
+impl<V: Clone> Rotate<V> for mat::Identity {
+    #[inline]
+    fn rotate(&self, v: &V) -> V {
+        v.clone()
+    }
+
+    #[inline]
+    fn inv_rotate(&self, v: &V) -> V {
+        v.clone()
+    }
+}
+
+impl<M: One> Transformation<M> for mat::Identity {
+    #[inline]
+    fn transformation(&self) -> M {
+        One::one()
+    }
+
+    #[inline]
+    fn inv_transformation(&self) -> M {
+        One::one()
+    }
+
+    #[inline]
+    fn transform_by(&mut self, _: &M) {
+        fail!("Attempted to transform the identity matrix.")
+    }
+
+    #[inline]
+    fn transformed(&self, _: &M) -> mat::Identity {
+        fail!("Attempted to transform the identity matrix.")
+    }
+}
+
+impl<V: Clone> Transform<V> for mat::Identity {
+    #[inline]
+    fn transform(&self, v: &V) -> V {
+        v.clone()
+    }
+
+    #[inline]
+    fn inv_transform(&self, v: &V) -> V {
+        v.clone()
+    }
+}

src/mat.rs

@@ -28,6 +28,18 @@ pub use traits::transpose::*;
 
 mod mat_macros;
 
+/// Special identity matrix. All its operation are no-ops.
+#[deriving(Eq, Encodable, Decodable, Clone, DeepClone, Rand, Zero, ToStr)]
+pub struct Identity;
+
+impl Identity {
+    /// Creates a new identity matrix.
+    #[inline]
+    pub fn new() -> Identity {
+        Identity
+    }
+}
+
 /// Square matrix of dimension 1.
 #[deriving(Eq, Encodable, Decodable, Clone, DeepClone, IterBytes, Rand, Zero, ToStr)]
 pub struct Mat1<N> {

src/nalgebra.rc

@@ -26,6 +26,7 @@ pub mod mat;
 mod mat_spec;
 mod vec_spec;
 mod vec0_spec;
+mod identity_spec;
 
 /// Wrappers around raw matrices to restrict their behaviour.
 pub mod adaptors

src/traits/rlmul.rs

@@ -3,7 +3,7 @@
  */
 pub trait RMul<V> {
     /// Computes self * v
-    fn rmul(&self, v : &V) -> V;
+    fn rmul(&self, v: &V) -> V;
 }
 
 /**

src/vec0_spec.rs

@@ -20,7 +20,7 @@ impl<N> vec::Vec0<N> {
     }
 }
 
-impl<N: Clone> Indexable<uint, N> for vec::Vec0<N> {
+impl<N> Indexable<uint, N> for vec::Vec0<N> {
     #[inline]
     fn at(&self, _: uint) -> N {
         fail!("Cannot index a Vec0.")
@@ -37,7 +37,7 @@ impl<N: Clone> Indexable<uint, N> for vec::Vec0<N> {
     }
 }
 
-impl<N: Clone> vec::Vec0<N> {
+impl<N> vec::Vec0<N> {
     /// Creates a new vector. The parameter is not taken in account.
     #[inline]
     pub fn new_repeat(_: N) -> vec::Vec0<N> {
@@ -66,7 +66,7 @@ impl<N> Dim for vec::Vec0<N> {
     }
 }
 
-impl<N: Clone + Num + Algebraic + ApproxEq<N>> Basis for vec::Vec0<N> {
+impl<N> Basis for vec::Vec0<N> {
     #[inline(always)]
     fn canonical_basis(_: &fn(vec::Vec0<N>) -> bool) { }