diff --git a/src/lib.rs b/src/lib.rs
index acc43fba..9c10add5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -92,7 +92,7 @@ extern crate num;
 extern crate quickcheck;
 
 use std::cmp;
-use std::ops::{Neg, Mul};
+use std::ops::Neg;
 use num::{Zero, One};
 pub use traits::{
     Absolute,
@@ -132,6 +132,7 @@ pub use traits::{
     POrd,
     POrdering,
     PntAsVec,
+    Repeat,
     Rotate, Rotation, RotationMatrix, RotationWithTranslation,
     Row,
     Shape,
@@ -575,9 +576,8 @@ pub fn append_rotation_wrt_center<LV: Neg<Output = LV> + Copy,
 /// Builds a rotation matrix from `r`.
 #[inline(always)]
 pub fn to_rot_mat<N, LV, AV, R, M>(r: &R) -> M
-    where R: RotationMatrix<N, LV, AV, Output=M>,
-          M: Mat<N, LV, AV> + Rotation<AV> + Col<LV> + Copy,
-          LV: Mul<M, Output=LV> + Copy,
+    where R: RotationMatrix<N, LV, AV, Output = M>,
+          M: SquareMat<N, LV> + Rotation<AV> + Copy
 {
     // FIXME: rust-lang/rust#20413
     r.to_rot_mat()
@@ -678,7 +678,7 @@ pub fn det<M: Det<N>, N>(m: &M) -> N {
 
 /// Computes the cross product of two vectors.
 #[inline(always)]
-pub fn cross<LV: Cross>(a: &LV, b: &LV) -> LV::Output {
+pub fn cross<LV: Cross>(a: &LV, b: &LV) -> LV::CrossProductType {
     Cross::cross(a, b)
 }
 
@@ -785,7 +785,7 @@ pub fn transpose<M: Transpose>(m: &M) -> M {
 
 /// Computes the outer product of two vectors.
 #[inline(always)]
-pub fn outer<V: Outer<M>, M>(a: &V, b: &V) -> M {
+pub fn outer<V: Outer>(a: &V, b: &V) -> V::OuterProductType {
     Outer::outer(a, b)
 }
 
@@ -833,6 +833,18 @@ pub fn new_identity<M: Eye>(dim: usize) -> M {
     Eye::new_identity(dim)
 }
 
+
+/*
+ * Repeat
+ */
+/// Create an object by repeating a value.
+///
+/// Same as `Identity::new()`.
+#[inline(always)]
+pub fn repeat<N, T: Repeat<N>>(val: N) -> T {
+    Repeat::repeat(val)
+}
+
 /*
  * Basis
  */
diff --git a/src/structs/dmat.rs b/src/structs/dmat.rs
index fa74d6c3..6d23b842 100644
--- a/src/structs/dmat.rs
+++ b/src/structs/dmat.rs
@@ -10,7 +10,7 @@ use rand::{self, Rand};
 use num::{Zero, One};
 use structs::dvec::DVec;
 use traits::operations::{ApproxEq, Inv, Transpose, Mean, Cov};
-use traits::structure::{Cast, ColSlice, RowSlice, Diag, Eye, Indexable, Shape, BaseNum};
+use traits::structure::{Cast, ColSlice, RowSlice, Diag, DiagMut, Eye, Indexable, Shape, BaseNum};
 #[cfg(feature="arbitrary")]
 use quickcheck::{Arbitrary, Gen};
 
@@ -555,17 +555,6 @@ impl<N: Copy + Clone + Zero>  Diag<DVec<N>> for DMat<N> {
         res
     }
 
-    #[inline]
-    fn set_diag(&mut self, diag: &DVec<N>) {
-        let smallest_dim = cmp::min(self.nrows, self.ncols);
-
-        assert!(diag.len() == smallest_dim);
-
-        for i in 0..smallest_dim {
-            unsafe { self.unsafe_set((i, i), diag.unsafe_at(i)) }
-        }
-    }
-
     #[inline]
     fn diag(&self) -> DVec<N> {
         let smallest_dim = cmp::min(self.nrows, self.ncols);
@@ -580,6 +569,19 @@ impl<N: Copy + Clone + Zero>  Diag<DVec<N>> for DMat<N> {
     }
 }
 
+impl<N: Copy + Clone + Zero>  DiagMut<DVec<N>> for DMat<N> {
+    #[inline]
+    fn set_diag(&mut self, diag: &DVec<N>) {
+        let smallest_dim = cmp::min(self.nrows, self.ncols);
+
+        assert!(diag.len() == smallest_dim);
+
+        for i in 0..smallest_dim {
+            unsafe { self.unsafe_set((i, i), diag.unsafe_at(i)) }
+        }
+    }
+}
+
 impl<N: ApproxEq<N>> ApproxEq<N> for DMat<N> {
     #[inline]
     fn approx_epsilon(_: Option<DMat<N>>) -> N {
diff --git a/src/structs/mat.rs b/src/structs/mat.rs
index c434d2bd..40604e9b 100644
--- a/src/structs/mat.rs
+++ b/src/structs/mat.rs
@@ -12,8 +12,8 @@ use structs::vec::{Vec1, Vec2, Vec3, Vec4, Vec5, Vec6};
 use structs::pnt::{Pnt1, Pnt4, Pnt5, Pnt6};
 use structs::dvec::{DVec1, DVec2, DVec3, DVec4, DVec5, DVec6};
 
-use traits::structure::{Cast, Row, Col, Iterable, IterableMut, Dim, Indexable,
-                        Eye, ColSlice, RowSlice, Diag, Shape, BaseFloat, BaseNum};
+use traits::structure::{Cast, Row, Col, Iterable, IterableMut, Dim, Indexable, Eye, ColSlice,
+                        RowSlice, Diag, DiagMut, Shape, BaseFloat, BaseNum, Repeat};
 use traits::operations::{Absolute, Transpose, Inv, Outer, EigenQR};
 use traits::geometry::{ToHomogeneous, FromHomogeneous, Orig};
 use linalg;
@@ -23,7 +23,7 @@ use quickcheck::{Arbitrary, Gen};
 
 /// Special identity matrix. All its operation are no-ops.
 #[repr(C)]
-#[derive(Eq, PartialEq, RustcDecodable, Clone, Debug, Copy)]
+#[derive(Eq, PartialEq, RustcEncodable, RustcDecodable, Clone, Debug, Copy)]
 pub struct Identity;
 
 impl Identity {
@@ -44,6 +44,7 @@ pub struct Mat1<N> {
 eye_impl!(Mat1, 1, m11);
 
 mat_impl!(Mat1, m11);
+repeat_impl!(Mat1, m11);
 as_array_impl!(Mat1, 1);
 mat_cast_impl!(Mat1, m11);
 add_impl!(Mat1, m11);
@@ -93,6 +94,8 @@ eye_impl!(Mat2, 2, m11, m22);
 
 mat_impl!(Mat2, m11, m12,
                 m21, m22);
+repeat_impl!(Mat2, m11, m12,
+                   m21, m22);
 as_array_impl!(Mat2, 2);
 mat_cast_impl!(Mat2, m11, m12,
                      m21, m22);
@@ -146,6 +149,9 @@ eye_impl!(Mat3, 3, m11, m22, m33);
 mat_impl!(Mat3, m11, m12, m13,
                 m21, m22, m23,
                 m31, m32, m33);
+repeat_impl!(Mat3, m11, m12, m13,
+                   m21, m22, m23,
+                   m31, m32, m33);
 as_array_impl!(Mat3, 3);
 mat_cast_impl!(Mat3, m11, m12, m13,
                      m21, m22, m23,
@@ -243,6 +249,12 @@ mat_impl!(Mat4,
   m31, m32, m33, m34,
   m41, m42, m43, m44
 );
+repeat_impl!(Mat4,
+  m11, m12, m13, m14,
+  m21, m22, m23, m24,
+  m31, m32, m33, m34,
+  m41, m42, m43, m44
+);
 as_array_impl!(Mat4, 4);
 mat_cast_impl!(Mat4,
   m11, m12, m13, m14,
@@ -358,6 +370,13 @@ mat_impl!(Mat5,
   m41, m42, m43, m44, m45,
   m51, m52, m53, m54, m55
 );
+repeat_impl!(Mat5,
+  m11, m12, m13, m14, m15,
+  m21, m22, m23, m24, m25,
+  m31, m32, m33, m34, m35,
+  m41, m42, m43, m44, m45,
+  m51, m52, m53, m54, m55
+);
 as_array_impl!(Mat5, 5);
 mat_cast_impl!(Mat5,
   m11, m12, m13, m14, m15,
@@ -489,6 +508,14 @@ mat_impl!(Mat6,
   m51, m52, m53, m54, m55, m56,
   m61, m62, m63, m64, m65, m66
 );
+repeat_impl!(Mat6,
+  m11, m12, m13, m14, m15, m16,
+  m21, m22, m23, m24, m25, m26,
+  m31, m32, m33, m34, m35, m36,
+  m41, m42, m43, m44, m45, m46,
+  m51, m52, m53, m54, m55, m56,
+  m61, m62, m63, m64, m65, m66
+);
 as_array_impl!(Mat6, 6);
 mat_cast_impl!(Mat6,
   m11, m12, m13, m14, m15, m16,
diff --git a/src/structs/mat_macros.rs b/src/structs/mat_macros.rs
index 5f268004..d95ffd2d 100644
--- a/src/structs/mat_macros.rs
+++ b/src/structs/mat_macros.rs
@@ -164,6 +164,18 @@ macro_rules! eye_impl(
     )
 );
 
+macro_rules! repeat_impl(
+    ($t: ident, $($compN: ident),+) => (
+        impl<N: Copy> Repeat<N> for $t<N> {
+            fn repeat(val: N) -> $t<N> {
+                $t {
+                    $($compN: val ),+
+                }
+            }
+        }
+    )
+);
+
 macro_rules! mat_sub_scalar_impl(
     ($t: ident, $($compN: ident),+) => (
         impl<N: Sub<N, Output = N> Sub<N> for $t<N> {
@@ -401,13 +413,6 @@ macro_rules! diag_impl(
                 res
             }
 
-            #[inline]
-            fn set_diag(&mut self, diag: &$tv<N>) {
-                for i in 0..$dim {
-                    unsafe { self.unsafe_set((i, i), diag.unsafe_at(i)) }
-                }
-            }
-
             #[inline]
             fn diag(&self) -> $tv<N> {
                 let mut diag: $tv<N> = ::zero();
@@ -419,6 +424,15 @@ macro_rules! diag_impl(
                 diag
             }
         }
+
+        impl<N: Copy + Zero> DiagMut<$tv<N>> for $t<N> {
+            #[inline]
+            fn set_diag(&mut self, diag: &$tv<N>) {
+                for i in 0..$dim {
+                    unsafe { self.unsafe_set((i, i), diag.unsafe_at(i)) }
+                }
+            }
+        }
     )
 );
 
@@ -688,7 +702,9 @@ macro_rules! from_homogeneous_impl(
 
 macro_rules! outer_impl(
     ($t: ident, $m: ident) => (
-        impl<N: Copy + Mul<N, Output = N> + Zero> Outer<$m<N>> for $t<N> {
+        impl<N: Copy + Mul<N, Output = N> + Zero> Outer for $t<N> {
+            type OuterProductType = $m<N>;
+
             #[inline]
             fn outer(&self, other: &$t<N>) -> $m<N> {
                 let mut res: $m<N> = ::zero();
diff --git a/src/structs/pnt.rs b/src/structs/pnt.rs
index fb01e1cd..b7452f19 100644
--- a/src/structs/pnt.rs
+++ b/src/structs/pnt.rs
@@ -11,7 +11,7 @@ use rand::{Rand, Rng};
 use num::{Zero, One};
 use traits::operations::{ApproxEq, POrd, POrdering, Axpy};
 use traits::structure::{Cast, Dim, Indexable, Iterable, IterableMut, PntAsVec, Shape,
-                        NumPnt, FloatPnt, BaseFloat, BaseNum, Bounded};
+                        NumPnt, FloatPnt, BaseFloat, BaseNum, Bounded, Repeat};
 use traits::geometry::{Orig, FromHomogeneous, ToHomogeneous};
 use structs::vec::{Vec1, Vec2, Vec3, Vec4, Vec5, Vec6};
 #[cfg(feature="arbitrary")]
@@ -29,10 +29,11 @@ impl<N> Pnt0<N> {
     pub fn new() -> Pnt0<N> {
         Pnt0(PhantomData)
     }
+}
 
-    /// Creates a new point. The parameter is not taken in account.
+impl<N> Repeat<N> for Pnt0<N> {
     #[inline]
-    pub fn new_repeat(_: N) -> Pnt0<N> {
+    fn repeat(_: N) -> Pnt0<N> {
         Pnt0(PhantomData)
     }
 }
@@ -57,7 +58,7 @@ as_array_impl!(Pnt1, 1);
 index_impl!(Pnt1);
 indexable_impl!(Pnt1, 1);
 at_fast_impl!(Pnt1, 1);
-new_repeat_impl!(Pnt1, val, x);
+repeat_impl!(Pnt1, val, x);
 dim_impl!(Pnt1, 1);
 container_impl!(Pnt1);
 pnt_as_vec_impl!(Pnt1, Vec1, x);
@@ -99,7 +100,7 @@ as_array_impl!(Pnt2, 2);
 index_impl!(Pnt2);
 indexable_impl!(Pnt2, 2);
 at_fast_impl!(Pnt2, 2);
-new_repeat_impl!(Pnt2, val, x, y);
+repeat_impl!(Pnt2, val, x, y);
 dim_impl!(Pnt2, 2);
 container_impl!(Pnt2);
 pnt_as_vec_impl!(Pnt2, Vec2, x, y);
@@ -143,7 +144,7 @@ as_array_impl!(Pnt3, 3);
 index_impl!(Pnt3);
 indexable_impl!(Pnt3, 3);
 at_fast_impl!(Pnt3, 3);
-new_repeat_impl!(Pnt3, val, x, y, z);
+repeat_impl!(Pnt3, val, x, y, z);
 dim_impl!(Pnt3, 3);
 container_impl!(Pnt3);
 pnt_as_vec_impl!(Pnt3, Vec3, x, y, z);
@@ -189,7 +190,7 @@ as_array_impl!(Pnt4, 4);
 index_impl!(Pnt4);
 indexable_impl!(Pnt4, 4);
 at_fast_impl!(Pnt4, 4);
-new_repeat_impl!(Pnt4, val, x, y, z, w);
+repeat_impl!(Pnt4, val, x, y, z, w);
 dim_impl!(Pnt4, 4);
 container_impl!(Pnt4);
 pnt_as_vec_impl!(Pnt4, Vec4, x, y, z, w);
@@ -237,7 +238,7 @@ as_array_impl!(Pnt5, 5);
 index_impl!(Pnt5);
 indexable_impl!(Pnt5, 5);
 at_fast_impl!(Pnt5, 5);
-new_repeat_impl!(Pnt5, val, x, y, z, w, a);
+repeat_impl!(Pnt5, val, x, y, z, w, a);
 dim_impl!(Pnt5, 5);
 container_impl!(Pnt5);
 pnt_as_vec_impl!(Pnt5, Vec5, x, y, z, w, a);
@@ -287,7 +288,7 @@ as_array_impl!(Pnt6, 6);
 index_impl!(Pnt6);
 indexable_impl!(Pnt6, 6);
 at_fast_impl!(Pnt6, 6);
-new_repeat_impl!(Pnt6, val, x, y, z, w, a, b);
+repeat_impl!(Pnt6, val, x, y, z, w, a, b);
 dim_impl!(Pnt6, 6);
 container_impl!(Pnt6);
 pnt_as_vec_impl!(Pnt6, Vec6, x, y, z, w, a, b);
diff --git a/src/structs/quat.rs b/src/structs/quat.rs
index 5c24e93a..24f70bc1 100644
--- a/src/structs/quat.rs
+++ b/src/structs/quat.rs
@@ -11,7 +11,7 @@ use num::{Zero, One};
 use structs::{Vec3, Pnt3, Rot3, Mat3};
 use traits::operations::{ApproxEq, Inv, POrd, POrdering, Axpy};
 use traits::structure::{Cast, Indexable, Iterable, IterableMut, Dim, Shape, BaseFloat, BaseNum,
-                        Bounded};
+                        Bounded, Repeat};
 use traits::geometry::{Norm, Rotation, Rotate, Transform};
 
 #[cfg(feature="arbitrary")]
@@ -495,7 +495,7 @@ as_array_impl!(Quat, 4);
 index_impl!(Quat);
 indexable_impl!(Quat, 4);
 at_fast_impl!(Quat, 4);
-new_repeat_impl!(Quat, val, w, i, j, k);
+repeat_impl!(Quat, val, w, i, j, k);
 dim_impl!(Quat, 3);
 container_impl!(Quat);
 add_impl!(Quat, w, i, j, k);
diff --git a/src/structs/rot.rs b/src/structs/rot.rs
index 2b97fdc3..dca149b4 100644
--- a/src/structs/rot.rs
+++ b/src/structs/rot.rs
@@ -7,7 +7,7 @@ use rand::{Rand, Rng};
 use num::{Zero, One};
 use traits::geometry::{Rotate, Rotation, AbsoluteRotate, RotationMatrix, Transform, ToHomogeneous,
                        Norm, Cross};
-use traits::structure::{Cast, Dim, Row, Col, BaseFloat, BaseNum, };
+use traits::structure::{Cast, Dim, Row, Col, BaseFloat, BaseNum, Eye, Diag};
 use traits::operations::{Absolute, Inv, Transpose, ApproxEq};
 use structs::vec::{Vec1, Vec2, Vec3, Vec4};
 use structs::pnt::{Pnt2, Pnt3, Pnt4};
@@ -408,6 +408,7 @@ vec_mul_rot_impl!(Rot2, Vec2);
 rot_mul_pnt_impl!(Rot2, Pnt2);
 pnt_mul_rot_impl!(Rot2, Pnt2);
 one_impl!(Rot2);
+eye_impl!(Rot2);
 rotation_matrix_impl!(Rot2, Vec2, Vec1);
 col_impl!(Rot2, Vec2);
 row_impl!(Rot2, Vec2);
@@ -417,6 +418,7 @@ to_homogeneous_impl!(Rot2, Mat3);
 inv_impl!(Rot2);
 transpose_impl!(Rot2);
 approx_eq_impl!(Rot2);
+diag_impl!(Rot2, Vec2);
 
 submat_impl!(Rot3, Mat3);
 rotate_impl!(Rot3, Vec3, Pnt3);
@@ -428,6 +430,7 @@ vec_mul_rot_impl!(Rot3, Vec3);
 rot_mul_pnt_impl!(Rot3, Pnt3);
 pnt_mul_rot_impl!(Rot3, Pnt3);
 one_impl!(Rot3);
+eye_impl!(Rot3);
 rotation_matrix_impl!(Rot3, Vec3, Vec3);
 col_impl!(Rot3, Vec3);
 row_impl!(Rot3, Vec3);
@@ -437,6 +440,7 @@ to_homogeneous_impl!(Rot3, Mat4);
 inv_impl!(Rot3);
 transpose_impl!(Rot3);
 approx_eq_impl!(Rot3);
+diag_impl!(Rot3, Vec3);
 
 submat_impl!(Rot4, Mat4);
 rotate_impl!(Rot4, Vec4, Pnt4);
@@ -448,6 +452,7 @@ vec_mul_rot_impl!(Rot4, Vec4);
 rot_mul_pnt_impl!(Rot4, Pnt4);
 pnt_mul_rot_impl!(Rot4, Pnt4);
 one_impl!(Rot4);
+eye_impl!(Rot4);
 rotation_matrix_impl!(Rot4, Vec4, Vec4);
 col_impl!(Rot4, Vec4);
 row_impl!(Rot4, Vec4);
@@ -457,3 +462,4 @@ to_homogeneous_impl!(Rot4, Mat5);
 inv_impl!(Rot4);
 transpose_impl!(Rot4);
 approx_eq_impl!(Rot4);
+diag_impl!(Rot4, Vec4);
diff --git a/src/structs/rot_macros.rs b/src/structs/rot_macros.rs
index 94928481..a9c38326 100644
--- a/src/structs/rot_macros.rs
+++ b/src/structs/rot_macros.rs
@@ -102,6 +102,38 @@ macro_rules! one_impl(
     )
 );
 
+macro_rules! eye_impl(
+    ($t: ident) => (
+        impl<N: BaseNum> Eye for $t<N> {
+            #[inline]
+            fn new_identity(dim: usize) -> $t<N> {
+                if dim != ::dim::<$t<N>>() {
+                    panic!("Dimension mismatch: should be {}, got {}.", ::dim::<$t<N>>(), dim);
+                }
+                else {
+                    ::one()
+                }
+            }
+        }
+    )
+);
+
+macro_rules! diag_impl(
+    ($t: ident, $tv: ident) => (
+        impl<N: Copy + Zero> Diag<$tv<N>> for $t<N> {
+            #[inline]
+            fn from_diag(diag: &$tv<N>) -> $t<N> {
+                $t { submat: Diag::from_diag(diag) }
+            }
+
+            #[inline]
+            fn diag(&self) -> $tv<N> {
+                self.submat.diag()
+            }
+        }
+    )
+);
+
 macro_rules! rot_mul_rot_impl(
     ($t: ident) => (
         impl<N: BaseNum> Mul<$t<N>> for $t<N> {
diff --git a/src/structs/spec/vec.rs b/src/structs/spec/vec.rs
index 59c1983b..fcb0fa1c 100644
--- a/src/structs/spec/vec.rs
+++ b/src/structs/spec/vec.rs
@@ -6,7 +6,7 @@ use structs::vec::{Vec1, Vec2, Vec3, Vec4};
 use structs::mat::Mat3;
 
 impl<N: Copy + Mul<N, Output = N> + Sub<N, Output = N>> Cross for Vec2<N> {
-    type Output = Vec1<N>;
+    type CrossProductType = Vec1<N>;
 
     #[inline]
     fn cross(&self, other: &Vec2<N>) -> Vec1<N> {
@@ -23,7 +23,7 @@ impl<N: Neg<Output = N> + Copy> CrossMatrix<Vec2<N>> for Vec2<N> {
 }
 
 impl<N: Copy + Mul<N, Output = N> + Sub<N, Output = N>> Cross for Vec3<N> {
-    type Output = Vec3<N>;
+    type CrossProductType = Vec3<N>;
 
     #[inline]
     fn cross(&self, other: &Vec3<N>) -> Vec3<N> {
diff --git a/src/structs/vec.rs b/src/structs/vec.rs
index 618689ad..318bcfad 100644
--- a/src/structs/vec.rs
+++ b/src/structs/vec.rs
@@ -13,7 +13,7 @@ use traits::operations::{ApproxEq, POrd, POrdering, Axpy, Absolute};
 use traits::geometry::{Transform, Rotate, FromHomogeneous, ToHomogeneous, Dot, Norm,
                        Translation, Translate};
 use traits::structure::{Basis, Cast, Dim, Indexable, Iterable, IterableMut, Shape, NumVec,
-                        FloatVec, BaseFloat, BaseNum, Bounded};
+                        FloatVec, BaseFloat, BaseNum, Bounded, Repeat};
 use structs::pnt::{Pnt1, Pnt2, Pnt3, Pnt4, Pnt5, Pnt6};
 
 #[cfg(feature="arbitrary")]
@@ -31,10 +31,11 @@ impl<N> Vec0<N> {
     pub fn new() -> Vec0<N> {
         Vec0(PhantomData)
     }
+}
 
-    /// Creates a new vector. The parameter is not taken in account.
+impl<N> Repeat<N> for Vec0<N> {
     #[inline]
-    pub fn new_repeat(_: N) -> Vec0<N> {
+    fn repeat(_: N) -> Vec0<N> {
         Vec0(PhantomData)
     }
 }
@@ -55,7 +56,7 @@ as_array_impl!(Vec1, 1);
 index_impl!(Vec1);
 indexable_impl!(Vec1, 1);
 at_fast_impl!(Vec1, 1);
-new_repeat_impl!(Vec1, val, x);
+repeat_impl!(Vec1, val, x);
 dim_impl!(Vec1, 1);
 container_impl!(Vec1);
 // (specialized); basis_impl!(Vec1, 1);
@@ -108,7 +109,7 @@ as_array_impl!(Vec2, 2);
 index_impl!(Vec2);
 indexable_impl!(Vec2, 2);
 at_fast_impl!(Vec2, 2);
-new_repeat_impl!(Vec2, val, x, y);
+repeat_impl!(Vec2, val, x, y);
 dim_impl!(Vec2, 2);
 container_impl!(Vec2);
 // (specialized); basis_impl!(Vec2, 1);
@@ -163,7 +164,7 @@ as_array_impl!(Vec3, 3);
 index_impl!(Vec3);
 indexable_impl!(Vec3, 3);
 at_fast_impl!(Vec3, 3);
-new_repeat_impl!(Vec3, val, x, y, z);
+repeat_impl!(Vec3, val, x, y, z);
 dim_impl!(Vec3, 3);
 container_impl!(Vec3);
 // (specialized); basis_impl!(Vec3, 1);
@@ -221,7 +222,7 @@ as_array_impl!(Vec4, 4);
 index_impl!(Vec4);
 indexable_impl!(Vec4, 4);
 at_fast_impl!(Vec4, 4);
-new_repeat_impl!(Vec4, val, x, y, z, w);
+repeat_impl!(Vec4, val, x, y, z, w);
 dim_impl!(Vec4, 4);
 container_impl!(Vec4);
 basis_impl!(Vec4, 4);
@@ -280,7 +281,7 @@ as_array_impl!(Vec5, 5);
 index_impl!(Vec5);
 indexable_impl!(Vec5, 5);
 at_fast_impl!(Vec5, 5);
-new_repeat_impl!(Vec5, val, x, y, z, w, a);
+repeat_impl!(Vec5, val, x, y, z, w, a);
 dim_impl!(Vec5, 5);
 container_impl!(Vec5);
 basis_impl!(Vec5, 5);
@@ -341,7 +342,7 @@ as_array_impl!(Vec6, 6);
 index_impl!(Vec6);
 indexable_impl!(Vec6, 6);
 at_fast_impl!(Vec6, 6);
-new_repeat_impl!(Vec6, val, x, y, z, w, a, b);
+repeat_impl!(Vec6, val, x, y, z, w, a, b);
 dim_impl!(Vec6, 6);
 container_impl!(Vec6);
 basis_impl!(Vec6, 6);
diff --git a/src/structs/vec_macros.rs b/src/structs/vec_macros.rs
index 42ecaf1d..8b92dd09 100644
--- a/src/structs/vec_macros.rs
+++ b/src/structs/vec_macros.rs
@@ -227,12 +227,12 @@ macro_rules! index_impl(
     )
 );
 
-macro_rules! new_repeat_impl(
+macro_rules! repeat_impl(
     ($t: ident, $param: ident, $($compN: ident),+) => (
-        impl<N: Copy> $t<N> {
+        impl<N: Copy> Repeat<N> for $t<N> {
             /// Creates a new vector with all its components equal to a given value.
             #[inline]
-            pub fn new_repeat($param: N) -> $t<N> {
+            fn repeat($param: N) -> $t<N> {
                 $t{
                     $($compN: $param ),+
                 }
diff --git a/src/traits/geometry.rs b/src/traits/geometry.rs
index e9c22678..29b3a51a 100644
--- a/src/traits/geometry.rs
+++ b/src/traits/geometry.rs
@@ -1,7 +1,7 @@
 //! Traits of operations having a well-known or explicit geometric meaning.
 
 use std::ops::Neg;
-use traits::structure::{BaseFloat, Mat};
+use traits::structure::{BaseFloat, SquareMat};
 
 /// Trait of object which represent a translation, and to wich new translation
 /// can be appended.
@@ -143,7 +143,7 @@ impl<LV: Neg<Output = LV> + Copy, AV, M: Rotation<AV> + Translation<LV>> Rotatio
 /// be implemented by quaternions to convert them to a rotation matrix.
 pub trait RotationMatrix<N, LV, AV> : Rotation<AV> {
     /// The output rotation matrix type.
-    type Output: Mat<N, LV, LV> + Rotation<AV>;
+    type Output: SquareMat<N, LV> + Rotation<AV>;
 
     /// Gets the rotation matrix represented by `self`.
     fn to_rot_mat(&self) -> Self::Output;
@@ -232,10 +232,10 @@ pub trait Norm<N: BaseFloat> {
  */
 pub trait Cross {
     /// The cross product output.
-    type Output;
+    type CrossProductType;
 
     /// Computes the cross product between two elements (usually vectors).
-    fn cross(&self, other: &Self) -> Self::Output;
+    fn cross(&self, other: &Self) -> Self::CrossProductType;
 }
 
 /**
diff --git a/src/traits/mod.rs b/src/traits/mod.rs
index 39d29c00..30506892 100644
--- a/src/traits/mod.rs
+++ b/src/traits/mod.rs
@@ -6,7 +6,8 @@ pub use traits::geometry::{AbsoluteRotate, Cross, CrossMatrix, Dot, FromHomogene
 
 pub use traits::structure::{FloatVec, FloatPnt, Basis, Cast, Col, Dim, Indexable, Iterable,
                             IterableMut, Mat, SquareMat, Row, NumVec, NumPnt, PntAsVec, ColSlice,
-                            RowSlice, Diag, Eye, Shape, BaseFloat, BaseNum, Bounded};
+                            RowSlice, Diag, DiagMut, Eye, Repeat, Shape, BaseFloat, BaseNum,
+                            Bounded};
 
 pub use traits::operations::{Absolute, ApproxEq, Axpy, Cov, Det, Inv, Mean, Outer, POrd, Transpose,
                              EigenQR};
diff --git a/src/traits/operations.rs b/src/traits/operations.rs
index b3bfeb54..f8a7ca74 100644
--- a/src/traits/operations.rs
+++ b/src/traits/operations.rs
@@ -299,9 +299,12 @@ pub trait Transpose {
 }
 
 /// Traits of objects having an outer product.
-pub trait Outer<M> {
+pub trait Outer {
+    /// Result type of the outer product.
+    type OuterProductType;
+
     /// Computes the outer product: `a * b`
-    fn outer(&self, other: &Self) -> M;
+    fn outer(&self, other: &Self) -> Self::OuterProductType;
 }
 
 /// Trait for computing the covariance of a set of data.
diff --git a/src/traits/structure.rs b/src/traits/structure.rs
index 79b4af4b..f579cdbe 100644
--- a/src/traits/structure.rs
+++ b/src/traits/structure.rs
@@ -59,12 +59,14 @@ pub trait Cast<T> {
 /// Trait of matrices.
 ///
 /// A matrix has rows and columns and are able to multiply them.
-pub trait Mat<N, R, C: Mul<Self>>: Row<R> + Col<C> + Mul<R> + Index<(usize, usize), Output = N> { }
+pub trait Mat<N, R, C: Mul<Self, Output = R>>: Row<R> + Col<C> + Mul<R, Output = C> +
+                                               Index<(usize, usize), Output = N>
+{ }
 
 impl<N, M, R, C> Mat<N, R, C> for M
-    where M: Row<R> + Col<C> + Mul<R> + Index<(usize, usize), Output = N>,
-          C: Mul<M>,
-{}
+    where M: Row<R> + Col<C> + Mul<R, Output = C> + Index<(usize, usize), Output = N>,
+          C: Mul<M, Output = R>,
+{ }
 
 /// Trait implemented by square matrices.
 pub trait SquareMat<N, V>: Mat<N, V, V> +
@@ -81,6 +83,12 @@ pub trait Eye {
     fn new_identity(dim: usize) -> Self;
 }
 
+/// Trait for constructiong an object repeating a value.
+pub trait Repeat<N> {
+    /// Returns a value with filled by `val`.
+    fn repeat(val: N) -> Self;
+}
+
 /// Types that have maximum and minimum value.
 pub trait Bounded {
     /// The minimum value.
@@ -155,13 +163,16 @@ pub trait Diag<V> {
     /// Creates a new matrix with the given diagonal.
     fn from_diag(diag: &V) -> Self;
 
-    /// Sets the diagonal of this matrix.
-    fn set_diag(&mut self, diag: &V);
-
     /// The diagonal of this matrix.
     fn diag(&self) -> V;
 }
 
+/// Trait to set the diagonal of square matrices.
+pub trait DiagMut<V>: Diag<V> {
+    /// Sets the diagonal of this matrix.
+    fn set_diag(&mut self, diag: &V);
+}
+
 /// The shape of an indexable object.
 pub trait Shape<I>: Index<I> {
     /// Returns the shape of an indexable object.