Add pointwise addition and subtraction for `DMat`.

Fix #132.

src/structs/dmat.rs

@@ -663,6 +663,24 @@ impl<N: Copy + Add<N, Output = N>> Add<N> for DMat<N> {
     }
 }
 
+impl<N: Copy + Add<N, Output = N>> Add<DMat<N>> for DMat<N> {
+    type Output = DMat<N>;
+
+    #[inline]
+    fn add(self, right: DMat<N>) -> DMat<N> {
+        assert!(self.nrows == right.nrows && self.ncols == right.ncols,
+                "Unable to add matrices with different dimensions.");
+
+        let mut res = self;
+
+        for (mij, right_ij) in res.mij.iter_mut().zip(right.mij.iter()) {
+            *mij = *mij + *right_ij;
+        }
+
+        res
+    }
+}
+
 impl<N: Copy + Sub<N, Output = N>> Sub<N> for DMat<N> {
     type Output = DMat<N>;
 
@@ -678,6 +696,24 @@ impl<N: Copy + Sub<N, Output = N>> Sub<N> for DMat<N> {
     }
 }
 
+impl<N: Copy + Sub<N, Output = N>> Sub<DMat<N>> for DMat<N> {
+    type Output = DMat<N>;
+
+    #[inline]
+    fn sub(self, right: DMat<N>) -> DMat<N> {
+        assert!(self.nrows == right.nrows && self.ncols == right.ncols,
+                "Unable to subtract matrices with different dimensions.");
+
+        let mut res = self;
+
+        for (mij, right_ij) in res.mij.iter_mut().zip(right.mij.iter()) {
+            *mij = *mij - *right_ij;
+        }
+
+        res
+    }
+}
+
 #[cfg(feature="arbitrary")]
 impl<N: Arbitrary> Arbitrary for DMat<N> {
     fn arbitrary<G: Gen>(g: &mut G) -> DMat<N> {

tests/mat.rs

@@ -290,6 +290,70 @@ fn test_dmat_from_vec() {
     assert!(mat1 == mat2);
 }
 
+#[test]
+fn test_dmat_addition() {
+    let mat1 = DMat::from_row_vec(
+        2,
+        2,
+        &[
+            1.0, 2.0,
+            3.0, 4.0
+        ]
+    );
+
+    let mat2 = DMat::from_row_vec(
+        2,
+        2,
+        &[
+            10.0, 20.0,
+            30.0, 40.0
+        ]
+    );
+
+    let res = DMat::from_row_vec(
+        2,
+        2,
+        &[
+            11.0, 22.0,
+            33.0, 44.0
+        ]
+    );
+
+    assert!((mat1 + mat2) == res);
+}
+
+#[test]
+fn test_dmat_subtraction() {
+    let mat1 = DMat::from_row_vec(
+        2,
+        2,
+        &[
+            1.0, 2.0,
+            3.0, 4.0
+        ]
+    );
+
+    let mat2 = DMat::from_row_vec(
+        2,
+        2,
+        &[
+            10.0, 20.0,
+            30.0, 40.0
+        ]
+    );
+
+    let res = DMat::from_row_vec(
+        2,
+        2,
+        &[
+            -09.0, -18.0,
+            -27.0, -36.0
+        ]
+    );
+
+    assert!((mat1 - mat2) == res);
+}
+
 /* FIXME: review qr decomposition to make it work with DMat.
 #[test]
 fn test_qr() {