diff --git a/src/mat.rs b/src/mat.rs
index f544299..2664427 100644
--- a/src/mat.rs
+++ b/src/mat.rs
@@ -149,6 +149,11 @@ pub trait MutableMatrix<T,V>: Matrix<T,V> {
      */
     fn swap_rows(&mut self, a: uint, b: uint);
     
+    /**
+     * Sets the matrix to `other` 
+     */
+    fn set(&mut self, other: &self);
+    
     /**
      * Sets the matrix to the identity matrix
      */
@@ -158,6 +163,36 @@ pub trait MutableMatrix<T,V>: Matrix<T,V> {
      * Sets each element of the matrix to zero
      */
     fn to_zero(&mut self);
+
+    /**
+     * Multiplies the matrix by a scalar
+     */
+    fn mul_self_t(&mut self, value: T);
+    
+    /**
+     * Add the matrix `other` to `self`
+     */
+    fn add_self_m(&mut self, other: &self);
+    
+    /**
+     * Subtract the matrix `other` from `self`
+     */
+    fn sub_self_m(&mut self, other: &self);
+    
+    /**
+     * Sets the matrix to its inverse
+     * 
+     * # Failure
+     *
+     * Fails if the matrix is not invertable. Make sure you check with the
+     * `is_invertible` method before you attempt this!
+     */
+    fn invert_self(&mut self);
+    
+    /**
+     * Sets the matrix to its transpose
+     */
+    fn transpose_self(&mut self);
 }
 
 /**
@@ -436,7 +471,7 @@ pub impl<T:Copy Float> Mat2<T>: Matrix<T, Vec2<T>> {
     }
 }
 
-pub impl<T:Copy Float> Mat2<T>: MutableMatrix<T, Vec2<T>> {
+pub impl<T:Copy Float Sign> Mat2<T>: MutableMatrix<T, Vec2<T>> {
     #[inline(always)]
     fn col_mut(&mut self, i: uint) -> &self/mut Vec2<T> {
         match i {
@@ -458,14 +493,51 @@ pub impl<T:Copy Float> Mat2<T>: MutableMatrix<T, Vec2<T>> {
         self.y.swap(a, b);
     }
     
+    #[inline(always)]
+    fn set(&mut self, other: &Mat2<T>) {
+        (*self) = (*other);
+    }
+    
     #[inline(always)]
     fn to_identity(&mut self) {
-        *self = Mat2::identity();
+        (*self) = Mat2::identity();
     }
     
     #[inline(always)]
     fn to_zero(&mut self) {
-        *self = Mat2::zero();
+        (*self) = Mat2::zero();
+    }
+    
+    #[inline(always)]
+    fn mul_self_t(&mut self, value: T) {
+        self.col_mut(0).mul_self_t(&value);
+        self.col_mut(1).mul_self_t(&value);
+    }
+    
+    #[inline(always)]
+    fn add_self_m(&mut self, other: &Mat2<T>) {
+        self.col_mut(0).add_self_v(&other[0]);
+        self.col_mut(1).add_self_v(&other[1]);
+    }
+    
+    #[inline(always)]
+    fn sub_self_m(&mut self, other: &Mat2<T>) {
+        self.col_mut(0).sub_self_v(&other[0]);
+        self.col_mut(1).sub_self_v(&other[1]);
+    }
+    
+    #[inline(always)]
+    fn invert_self(&mut self) {
+        match self.inverse() {
+            Some(m) => (*self) = m,
+            None => fail(~"Couldn't invert the matrix!")
+        }
+    }
+    
+    #[inline(always)]
+    fn transpose_self(&mut self) {
+        util::swap(self.col_mut(0).index_mut(1), self.col_mut(1).index_mut(0));
+        util::swap(self.col_mut(1).index_mut(0), self.col_mut(0).index_mut(1));
     }
 }
 
@@ -844,7 +916,7 @@ pub impl<T:Copy Float> Mat3<T>: Matrix<T, Vec3<T>> {
     }
 }
 
-pub impl<T:Copy Float> Mat3<T>: MutableMatrix<T, Vec3<T>> {
+pub impl<T:Copy Float Sign> Mat3<T>: MutableMatrix<T, Vec3<T>> {
     #[inline(always)]
     fn col_mut(&mut self, i: uint) -> &self/mut Vec3<T> {
         match i {
@@ -868,14 +940,60 @@ pub impl<T:Copy Float> Mat3<T>: MutableMatrix<T, Vec3<T>> {
         self.z.swap(a, b);
     }
     
+    #[inline(always)]
+    fn set(&mut self, other: &Mat3<T>) {
+        (*self) = (*other);
+    }
+    
     #[inline(always)]
     fn to_identity(&mut self) {
-        *self = Mat3::identity();
+        (*self) = Mat3::identity();
     }
     
     #[inline(always)]
     fn to_zero(&mut self) {
-        *self = Mat3::zero();
+        (*self) = Mat3::zero();
+    }
+    
+    #[inline(always)]
+    fn mul_self_t(&mut self, value: T) {
+        self.col_mut(0).mul_self_t(&value);
+        self.col_mut(1).mul_self_t(&value);
+        self.col_mut(2).mul_self_t(&value);
+    }
+    
+    #[inline(always)]
+    fn add_self_m(&mut self, other: &Mat3<T>) {
+        self.col_mut(0).add_self_v(&other[0]);
+        self.col_mut(1).add_self_v(&other[1]);
+        self.col_mut(2).add_self_v(&other[2]);
+    }
+    
+    #[inline(always)]
+    fn sub_self_m(&mut self, other: &Mat3<T>) {
+        self.col_mut(0).sub_self_v(&other[0]);
+        self.col_mut(1).sub_self_v(&other[1]);
+        self.col_mut(2).sub_self_v(&other[2]);
+    }
+    
+    #[inline(always)]
+    fn invert_self(&mut self) {
+        match self.inverse() {
+            Some(m) => (*self) = m,
+            None => fail(~"Couldn't invert the matrix!")
+        }
+    }
+    
+    #[inline(always)]
+    fn transpose_self(&mut self) {
+        util::swap(self.col_mut(0).index_mut(1), self.col_mut(1).index_mut(0));
+        util::swap(self.col_mut(0).index_mut(2), self.col_mut(2).index_mut(0));
+        
+        util::swap(self.col_mut(1).index_mut(0), self.col_mut(0).index_mut(1));
+        util::swap(self.col_mut(1).index_mut(2), self.col_mut(2).index_mut(1));
+        
+        util::swap(self.col_mut(2).index_mut(0), self.col_mut(0).index_mut(2));
+        util::swap(self.col_mut(2).index_mut(1), self.col_mut(1).index_mut(2));
     }
 }
 
@@ -1403,7 +1521,7 @@ pub impl<T:Copy Float Sign> Mat4<T>: Matrix<T, Vec4<T>> {
     }
 }
 
-pub impl<T:Copy Float> Mat4<T>: MutableMatrix<T, Vec4<T>> {
+pub impl<T:Copy Float Sign> Mat4<T>: MutableMatrix<T, Vec4<T>> {
     #[inline(always)]
     fn col_mut(&mut self, i: uint) -> &self/mut Vec4<T> {
         match i {
@@ -1429,14 +1547,70 @@ pub impl<T:Copy Float> Mat4<T>: MutableMatrix<T, Vec4<T>> {
         self.w.swap(a, b);
     }
     
+    #[inline(always)]
+    fn set(&mut self, other: &Mat4<T>) {
+        (*self) = (*other);
+    }
+    
     #[inline(always)]
     fn to_identity(&mut self) {
-        *self = Mat4::identity();
+        (*self) = Mat4::identity();
     }
     
     #[inline(always)]
     fn to_zero(&mut self) {
-        *self = Mat4::zero();
+        (*self) = Mat4::zero();
+    }
+    
+    #[inline(always)]
+    fn mul_self_t(&mut self, value: T) {
+        self.col_mut(0).mul_self_t(&value);
+        self.col_mut(1).mul_self_t(&value);
+        self.col_mut(2).mul_self_t(&value);
+        self.col_mut(3).mul_self_t(&value);
+    }
+    
+    #[inline(always)]
+    fn add_self_m(&mut self, other: &Mat4<T>) {
+        self.col_mut(0).add_self_v(&other[0]);
+        self.col_mut(1).add_self_v(&other[1]);
+        self.col_mut(2).add_self_v(&other[2]);
+        self.col_mut(3).add_self_v(&other[3]);
+    }
+    
+    #[inline(always)]
+    fn sub_self_m(&mut self, other: &Mat4<T>) {
+        self.col_mut(0).sub_self_v(&other[0]);
+        self.col_mut(1).sub_self_v(&other[1]);
+        self.col_mut(2).sub_self_v(&other[2]);
+        self.col_mut(3).sub_self_v(&other[3]);
+    }
+    
+    #[inline(always)]
+    fn invert_self(&mut self) {
+        match self.inverse() {
+            Some(m) => (*self) = m,
+            None => fail(~"Couldn't invert the matrix!")
+        }
+    }
+    
+    #[inline(always)]
+    fn transpose_self(&mut self) {
+        util::swap(self.col_mut(0).index_mut(1), self.col_mut(1).index_mut(0));
+        util::swap(self.col_mut(0).index_mut(2), self.col_mut(2).index_mut(0));
+        util::swap(self.col_mut(0).index_mut(3), self.col_mut(3).index_mut(0));
+        
+        util::swap(self.col_mut(1).index_mut(0), self.col_mut(0).index_mut(1));
+        util::swap(self.col_mut(1).index_mut(2), self.col_mut(2).index_mut(1));
+        util::swap(self.col_mut(1).index_mut(3), self.col_mut(3).index_mut(1));
+        
+        util::swap(self.col_mut(2).index_mut(0), self.col_mut(0).index_mut(2));
+        util::swap(self.col_mut(2).index_mut(1), self.col_mut(1).index_mut(2));
+        util::swap(self.col_mut(2).index_mut(3), self.col_mut(3).index_mut(2));
+        
+        util::swap(self.col_mut(3).index_mut(0), self.col_mut(0).index_mut(3));
+        util::swap(self.col_mut(3).index_mut(1), self.col_mut(1).index_mut(3));
+        util::swap(self.col_mut(3).index_mut(2), self.col_mut(2).index_mut(3));
     }
 }
 
diff --git a/src/test/test_mat.rs b/src/test/test_mat.rs
index 39d7c50..70003a6 100644
--- a/src/test/test_mat.rs
+++ b/src/test/test_mat.rs
@@ -10,8 +10,6 @@ fn test_Mat2() {
     let b = Mat2 { x: Vec2 { x: 2f, y: 4f },
                    y: Vec2 { x: 3f, y: 5f } };
     
-    let mut mut_a = a;
-    
     let v1 = Vec2::new(1f, 2f);
     let f1 = 0.5f;
     
@@ -33,28 +31,11 @@ fn test_Mat2() {
     assert a.col(0) == Vec2::new(1f, 3f);
     assert a.col(1) == Vec2::new(2f, 4f);
     
-    mut_a.swap_cols(0, 1);
-    assert mut_a.col(0) == a.col(1);
-    assert mut_a.col(1) == a.col(0);
-    mut_a = a;
-    
-    mut_a.swap_rows(0, 1);
-    assert mut_a.row(0) == a.row(1);
-    assert mut_a.row(1) == a.row(0);
-    mut_a = a;
-    
     assert Mat2::identity() == Mat2::new(1f, 0f,
                                          0f, 1f);
-    mut_a.to_identity();
-    assert mut_a.is_identity();
-    mut_a = a;
     
     assert Mat2::zero() == Mat2::new(0f, 0f,
                                      0f, 0f);
-    
-    mut_a.to_zero();
-    assert mut_a == Mat2::new(0f, 0f,
-                              0f, 0f);
 
     assert a.determinant() == -2f;
     assert a.trace() == 5f;
@@ -123,6 +104,59 @@ fn test_Mat2() {
                                     0f, 0f, 0f, 1f);
 }
 
+fn test_Mat2_mut() {
+    let a = Mat2 { x: Vec2 { x: 1f, y: 3f },
+                   y: Vec2 { x: 2f, y: 4f } };
+    let b = Mat2 { x: Vec2 { x: 2f, y: 4f },
+                   y: Vec2 { x: 3f, y: 5f } };
+    
+    let f1 = 0.5f;
+    
+    let mut mut_a = a;
+    
+    mut_a.swap_cols(0, 1);
+    assert mut_a.col(0) == a.col(1);
+    assert mut_a.col(1) == a.col(0);
+    mut_a = a;
+    
+    mut_a.swap_rows(0, 1);
+    assert mut_a.row(0) == a.row(1);
+    assert mut_a.row(1) == a.row(0);
+    mut_a = a;
+    
+    mut_a.set(&b);
+    assert mut_a == b;
+    mut_a = a;
+    
+    mut_a.to_identity();
+    assert mut_a.is_identity();
+    mut_a = a;
+    
+    mut_a.to_zero();
+    assert mut_a == Mat2::zero();
+    mut_a = a;
+    
+    mut_a.mul_self_t(f1);
+    assert mut_a == a.mul_t(f1);
+    mut_a = a;
+    
+    mut_a.add_self_m(&b);
+    assert mut_a == a.add_m(&b);
+    mut_a = a;
+    
+    mut_a.sub_self_m(&b);
+    assert mut_a == a.sub_m(&b);
+    mut_a = a;
+    
+    mut_a.invert_self();
+    assert mut_a == option::unwrap(a.inverse());
+    mut_a = a;
+    
+    mut_a.transpose_self();
+    assert mut_a == a.transpose();
+    // mut_a = a;
+}
+
 #[test]
 fn test_Mat3() {
     let a = Mat3 { x: Vec3 { x: 1f, y: 4f, z:  7f },
@@ -132,8 +166,6 @@ fn test_Mat3() {
                    y: Vec3 { x: 3f, y: 6f, z:  9f },
                    z: Vec3 { x: 4f, y: 7f, z: 10f } };
     
-    let mut mut_a = a;
-    
     let v1 = Vec3::new(1f, 2f, 3f);
     let f1 = 0.5f;
     
@@ -166,40 +198,13 @@ fn test_Mat3() {
     assert a.col(1) == Vec3::new(2f, 5f, 8f);
     assert a.col(2) == Vec3::new(3f, 6f, 9f);
     
-    mut_a.swap_cols(0, 2);
-    assert mut_a.col(0) == a.col(2);
-    assert mut_a.col(2) == a.col(0);
-    mut_a = a;
-    
-    mut_a.swap_cols(1, 2);
-    assert mut_a.col(1) == a.col(2);
-    assert mut_a.col(2) == a.col(1);
-    mut_a = a;
-    
-    mut_a.swap_rows(0, 2);
-    assert mut_a.row(0) == a.row(2);
-    assert mut_a.row(2) == a.row(0);
-    mut_a = a;
-    
-    mut_a.swap_rows(1, 2);
-    assert mut_a.row(1) == a.row(2);
-    assert mut_a.row(2) == a.row(1);
-    mut_a = a;
-    
     assert Mat3::identity() == Mat3::new(1f, 0f, 0f,
                                          0f, 1f, 0f,
                                          0f, 0f, 1f);
-    mut_a.to_identity();
-    assert mut_a.is_identity();
-    mut_a = a;
     
     assert Mat3::zero() == Mat3::new(0f, 0f, 0f,
                                      0f, 0f, 0f,
                                      0f, 0f, 0f);
-    mut_a.to_zero();
-    assert mut_a == Mat3::new(0f, 0f, 0f,
-                              0f, 0f, 0f,
-                              0f, 0f, 0f);
 
     assert a.determinant() == 0f;
     assert a.trace() == 15f;
@@ -278,6 +283,75 @@ fn test_Mat3() {
     // to_Quaternion
 }
 
+fn test_Mat3_mut() {
+    let a = Mat3 { x: Vec3 { x: 1f, y: 4f, z:  7f },
+                   y: Vec3 { x: 2f, y: 5f, z:  8f },
+                   z: Vec3 { x: 3f, y: 6f, z:  9f } };
+    let b = Mat3 { x: Vec3 { x: 2f, y: 5f, z:  8f },
+                   y: Vec3 { x: 3f, y: 6f, z:  9f },
+                   z: Vec3 { x: 4f, y: 7f, z: 10f } };
+    let c = Mat3 { x: Vec3 { x: 2f, y: 4f, z:  6f },
+                   y: Vec3 { x: 0f, y: 2f, z:  4f },
+                   z: Vec3 { x: 0f, y: 0f, z:  1f } };
+    
+    let f1 = 0.5f;
+    
+    let mut mut_a = a;
+    let mut mut_c = c;
+    
+    mut_a.swap_cols(0, 2);
+    assert mut_a.col(0) == a.col(2);
+    assert mut_a.col(2) == a.col(0);
+    mut_a = a;
+    
+    mut_a.swap_cols(1, 2);
+    assert mut_a.col(1) == a.col(2);
+    assert mut_a.col(2) == a.col(1);
+    mut_a = a;
+    
+    mut_a.swap_rows(0, 2);
+    assert mut_a.row(0) == a.row(2);
+    assert mut_a.row(2) == a.row(0);
+    mut_a = a;
+    
+    mut_a.swap_rows(1, 2);
+    assert mut_a.row(1) == a.row(2);
+    assert mut_a.row(2) == a.row(1);
+    mut_a = a;
+    
+    mut_a.set(&b);
+    assert mut_a == b;
+    mut_a = a;
+    
+    mut_a.to_identity();
+    assert mut_a.is_identity();
+    mut_a = a;
+    
+    mut_a.to_zero();
+    assert mut_a == Mat3::zero();
+    mut_a = a;
+    
+    mut_a.mul_self_t(f1);
+    assert mut_a == a.mul_t(f1);
+    mut_a = a;
+    
+    mut_a.add_self_m(&b);
+    assert mut_a == a.add_m(&b);
+    mut_a = a;
+    
+    mut_a.sub_self_m(&b);
+    assert mut_a == a.sub_m(&b);
+    mut_a = a;
+    
+    mut_c.invert_self();
+    assert mut_c == option::unwrap(c.inverse());
+    // mut_c = c;
+    
+    mut_a.transpose_self();
+    assert mut_a == a.transpose();
+    // mut_a = a;
+}
+
 #[test]
 fn test_Mat4() {
     let a = Mat4 { x: Vec4 { x: 1f, y: 5f, z:  9f, w: 13f },
@@ -293,8 +367,6 @@ fn test_Mat4() {
                    z: Vec4 { x: 1f, y: 2f, z:  3f, w:  3f },
                    w: Vec4 { x: 0f, y: 1f, z:  1f, w:  0f } };
     
-    let mut mut_a = a;
-    
     let v1 = Vec4::new(1f, 2f, 3f, 4f);
     let f1 = 0.5f;
     
@@ -341,43 +413,15 @@ fn test_Mat4() {
     assert a.col(2) == Vec4::new(3f, 7f, 11f, 15f);
     assert a.col(3) == Vec4::new(4f, 8f, 12f, 16f);
     
-    mut_a.swap_cols(0, 3);
-    assert mut_a.col(0) == a.col(3);
-    assert mut_a.col(3) == a.col(0);
-    mut_a = a;
-    
-    mut_a.swap_cols(1, 2);
-    assert mut_a.col(1) == a.col(2);
-    assert mut_a.col(2) == a.col(1);
-    mut_a = a;
-    
-    mut_a.swap_rows(0, 3);
-    assert mut_a.row(0) == a.row(3);
-    assert mut_a.row(3) == a.row(0);
-    mut_a = a;
-    
-    mut_a.swap_rows(1, 2);
-    assert mut_a.row(1) == a.row(2);
-    assert mut_a.row(2) == a.row(1);
-    mut_a = a;
-    
     assert Mat4::identity() == Mat4::new(1f, 0f, 0f, 0f,
                                          0f, 1f, 0f, 0f,
                                          0f, 0f, 1f, 0f,
                                          0f, 0f, 0f, 1f);
-    mut_a.to_identity();
-    assert mut_a.is_identity();
-    mut_a = a;
     
     assert Mat4::zero() == Mat4::new(0f, 0f, 0f, 0f,
                                      0f, 0f, 0f, 0f,
                                      0f, 0f, 0f, 0f,
                                      0f, 0f, 0f, 0f);
-    mut_a.to_zero();
-    assert mut_a == Mat4::new(0f, 0f, 0f, 0f,
-                              0f, 0f, 0f, 0f,
-                              0f, 0f, 0f, 0f,
-                              0f, 0f, 0f, 0f);
 
     assert a.determinant() == 0f;
     assert a.trace() == 34f;
@@ -452,3 +496,75 @@ fn test_Mat4() {
     
     assert Mat4::from_value(6f).is_diagonal();
 }
+
+fn test_Mat4_mut() {
+    let a = Mat4 { x: Vec4 { x: 1f, y: 5f, z:  9f, w: 13f },
+                   y: Vec4 { x: 2f, y: 6f, z: 10f, w: 14f },
+                   z: Vec4 { x: 3f, y: 7f, z: 11f, w: 15f },
+                   w: Vec4 { x: 4f, y: 8f, z: 12f, w: 16f } };
+    let b = Mat4 { x: Vec4 { x: 2f, y: 6f, z: 10f, w: 14f },
+                   y: Vec4 { x: 3f, y: 7f, z: 11f, w: 15f },
+                   z: Vec4 { x: 4f, y: 8f, z: 12f, w: 16f },
+                   w: Vec4 { x: 5f, y: 9f, z: 13f, w: 17f } };
+    let c = Mat4 { x: Vec4 { x: 3f, y: 2f, z:  1f, w:  1f },
+                   y: Vec4 { x: 2f, y: 3f, z:  2f, w:  2f },
+                   z: Vec4 { x: 1f, y: 2f, z:  3f, w:  3f },
+                   w: Vec4 { x: 0f, y: 1f, z:  1f, w:  0f } };
+    
+    let f1 = 0.5f;
+    
+    let mut mut_a = a;
+    let mut mut_c = c;
+    
+    mut_a.swap_cols(0, 3);
+    assert mut_a.col(0) == a.col(3);
+    assert mut_a.col(3) == a.col(0);
+    mut_a = a;
+    
+    mut_a.swap_cols(1, 2);
+    assert mut_a.col(1) == a.col(2);
+    assert mut_a.col(2) == a.col(1);
+    mut_a = a;
+    
+    mut_a.swap_rows(0, 3);
+    assert mut_a.row(0) == a.row(3);
+    assert mut_a.row(3) == a.row(0);
+    mut_a = a;
+    
+    mut_a.swap_rows(1, 2);
+    assert mut_a.row(1) == a.row(2);
+    assert mut_a.row(2) == a.row(1);
+    mut_a = a;
+    
+    mut_a.set(&b);
+    assert mut_a == b;
+    mut_a = a;
+    
+    mut_a.to_identity();
+    assert mut_a.is_identity();
+    mut_a = a;
+    
+    mut_a.to_zero();
+    assert mut_a == Mat4::zero();
+    mut_a = a;
+    
+    mut_a.mul_self_t(f1);
+    assert mut_a == a.mul_t(f1);
+    mut_a = a;
+    
+    mut_a.add_self_m(&b);
+    assert mut_a == a.add_m(&b);
+    mut_a = a;
+    
+    mut_a.sub_self_m(&b);
+    assert mut_a == a.sub_m(&b);
+    mut_a = a;
+    
+    mut_c.invert_self();
+    assert mut_c == option::unwrap(c.inverse());
+    // mut_c = c;
+    
+    mut_a.transpose_self();
+    assert mut_a == a.transpose();
+    // mut_a = a;
+}