Change width to size, as it is more correct.

Add calculation of determinant, submatric, minorm cofactor and inverse of a matrix.

source/include/matrix.h

@@ -13,24 +13,30 @@
 
 class Matrix
 {
-private:
+protected:
     /* 4x4 is the default */
     double data[4*4];
-    int width;
+    int size;
 
 public:
-    Matrix(int width);
-    Matrix(double values[], int width);
+    Matrix(int size);
+    Matrix(double values[], int size);
 
-    double get(int x, int y) const { return this->data[this->width * x + y]; };
-    void set(int x, int y, double v) { this->data[this->width * x + y] = v; };
+    double get(int x, int y) const { return this->data[this->size * x + y]; };
+    void set(int x, int y, double v) { this->data[this->size * x + y] = v; };
 
     Matrix identity();
     Matrix transpose();
-
+    double determinant();
+    Matrix submatrix(int row, int column);
+    Matrix inverse();
+    double minor(int row, int column) { return this->submatrix(row, column).determinant(); }
+    double cofactor(int row, int column) { return (((column+row)&1)?-1:1) * this->minor(row, column); }
     bool operator==(const Matrix &b) const;
     bool operator!=(const Matrix &b) const;
 
+    bool isInvertible() { return this->determinant() != 0; }
+
     Matrix operator*(const Matrix &b) const;
     Tuple operator*(const Tuple &b) const;
 };
@@ -42,14 +48,6 @@ public:
     Matrix4(double values[]) : Matrix(values, 4) { };
 };
 
-
-class Matrix2 : public Matrix
-{
-public:
-    Matrix2() : Matrix(2) { };
-    Matrix2(double values[]) : Matrix(values, 2) { };
-};
-
 class Matrix3 : public Matrix
 {
 public:
@@ -57,4 +55,13 @@ public:
     Matrix3(double values[]) : Matrix(values, 3) { };
 };
 
+class Matrix2 : public Matrix
+{
+private:
+    using Matrix::data;
+public:
+    Matrix2() : Matrix(2) { };
+    Matrix2(double values[]) : Matrix(values, 2) { };
+};
+
 #endif /* DORAYME_MATRIX_H */