core: add the unary minus operator to vectors.

src/matrix.h

@@ -103,6 +103,14 @@ namespace lol
         return ret; \
     } \
     \
+    inline Vec##elems<T> operator -() const \
+    { \
+        Vec##elems<T> ret; \
+        for (int n = 0; n < elems; n++) \
+            ret[n] = -(*this)[n]; \
+        return ret; \
+    } \
+    \
     inline T sqlen() const \
     { \
         T acc = 0; \

test/matrix.cpp

@@ -27,6 +27,7 @@ class MatrixTest : public CppUnit::TestCase
     CPPUNIT_TEST_SUITE(MatrixTest);
     CPPUNIT_TEST(test_vec_eq);
     CPPUNIT_TEST(test_vec_lt);
+    CPPUNIT_TEST(test_vec_unary);
     CPPUNIT_TEST(test_mat_det);
     CPPUNIT_TEST(test_mat_mul);
     CPPUNIT_TEST(test_mat_inv);
@@ -122,6 +123,15 @@ public:
         CPPUNIT_ASSERT(a2 < f2);
     }
 
+    void test_vec_unary()
+    {
+        vec2 a(1.0f, 3.0f);
+        vec2 b(-1.0f, -3.0f);
+
+        CPPUNIT_ASSERT(a == -b);
+        CPPUNIT_ASSERT(-a == b);
+    }
+
     void test_mat_det()
     {
         float d1 = triangular.det();