allow rectangular matrixes

matrix/src/lib.rs

@@ -6,24 +6,24 @@ use structs::Tuple;
 use std::ops::Index;
 
 #[derive(Debug)]
-pub struct Matrix<const COUNT: usize> {
-    matrix: [[f32; COUNT]; COUNT],
+pub struct Matrix<const H: usize, const W: usize> {
+    matrix: [[f32; W]; H],
 }
 
-impl<const COUNT: usize> Matrix<COUNT> {
-    pub fn new() -> Matrix<COUNT> {
+impl<const H: usize, const W: usize> Matrix<H, W> {
+    pub fn new() -> Matrix<H, W> {
         Matrix {
-            matrix: [[0f32; COUNT]; COUNT],
+            matrix: [[0f32; W]; H],
         }
     }
 
-    pub fn from_array(matrix: [[f32; COUNT]; COUNT]) -> Matrix<COUNT> {
+    pub fn from_array(matrix: [[f32; W]; H]) -> Matrix<H, W> {
         Matrix {
             matrix: matrix,
         }
     }
 
-    pub fn identity() -> Matrix<COUNT> {
+    pub fn identity() -> Matrix<H, W> {
         let mut m = Matrix::new();
         for i in 0..m.matrix.len() {
             m.matrix[i][i] = 1.0;
@@ -32,24 +32,28 @@ impl<const COUNT: usize> Matrix<COUNT> {
     }
 
     pub fn transpose(&mut self) {
-        let tmp = [
-            [self.matrix[0][0], self.matrix[1][0], self.matrix[2][0], self.matrix[3][0], ],
-            [self.matrix[0][1], self.matrix[1][1], self.matrix[2][1], self.matrix[3][1], ],
-            [self.matrix[0][2], self.matrix[1][2], self.matrix[2][2], self.matrix[3][2], ],
-            [self.matrix[0][3], self.matrix[1][3], self.matrix[2][3], self.matrix[3][3], ],
-        ];
-        self.matrix = tmp;
+        for i in 0..self.matrix.len() {
+            for j in i..self.matrix[0].len() {
+                let v = self.matrix[i][j];
+                self.matrix[i][j] = self.matrix[j][i];
+                self.matrix[j][i] = v;
+            }
+        }
+    }
+
+    pub fn determinant(&self) -> f32 {
+        self.matrix[0][0] * self.matrix[1][1] - self.matrix[0][1] * self.matrix[1][0]
     }
 }
 
-impl<const COUNT: usize> Index<usize> for Matrix<COUNT> {
-    type Output = [f32; COUNT];
+impl<const H: usize, const W: usize> Index<usize> for Matrix<H, W> {
+    type Output = [f32; W];
     fn index(&self, index: usize) -> &Self::Output {
         &self.matrix[index]
     }
 }
 
-impl<const COUNT: usize> PartialEq for Matrix<COUNT> {
+impl<const H: usize, const W: usize> PartialEq for Matrix<H, W> {
     fn eq(&self, _rhs: &Self) -> bool {
         if self.matrix.len() != _rhs.matrix.len() {
             return false;
@@ -69,10 +73,10 @@ impl<const COUNT: usize> PartialEq for Matrix<COUNT> {
     }
 }
 
-impl<const COUNT: usize> Matrix<COUNT> {
-    fn calc_val_for_mul(&self, row: usize, rhs: &Matrix<COUNT>, col: usize) -> f32 {
+impl<const H: usize, const W: usize> Matrix<H, W> {
+    fn calc_val_for_mul(&self, row: usize, rhs: &Matrix<H, W>, col: usize) -> f32 {
         let mut sum = 0.0;
-        for i in 0..self.matrix.len() {
+        for i in 0..W {
             sum += self.matrix[row][i] * rhs.matrix[i][col];
         }
         sum
@@ -86,13 +90,13 @@ impl<const COUNT: usize> Matrix<COUNT> {
     }
 }
 
-impl<const COUNT: usize> std::ops::Mul<Matrix<COUNT>> for Matrix<COUNT> {
-    type Output = Matrix<COUNT>;
+impl<const H: usize, const W: usize> std::ops::Mul<Matrix<H, W>> for Matrix<H, W> {
+    type Output = Matrix<H, W>;
 
-    fn mul(self, _rhs: Matrix<COUNT>) -> Matrix<COUNT> {
-        let mut result = [[0f32; COUNT]; COUNT];
-        for row in 0..COUNT {
-            for col in 0..COUNT {
+    fn mul(self, _rhs: Matrix<H, W>) -> Matrix<H, W> {
+        let mut result = [[0f32; W]; H];
+        for row in 0..H {
+            for col in 0..W {
                 result[row][col] = self.calc_val_for_mul(row, &_rhs, col);
             }
         }
@@ -101,7 +105,7 @@ impl<const COUNT: usize> std::ops::Mul<Matrix<COUNT>> for Matrix<COUNT> {
 
 }
 
-impl<const COUNT: usize> std::ops::Mul<Tuple> for Matrix<COUNT> {
+impl<const H: usize, const W: usize> std::ops::Mul<Tuple> for Matrix<H, W> {
     type Output = Tuple;
 
     fn mul(self, _rhs: Tuple) -> Tuple {
@@ -292,7 +296,7 @@ mod tests {
         let t = Tuple::new(1.0, 2.0, 3.0, 4.0);
         let expected = Tuple::new(1.0, 2.0, 3.0, 4.0);
 
-        assert_eq!(Matrix::<4>::identity() * t, expected);
+        assert_eq!(Matrix::<4, 4>::identity() * t, expected);
     }
 
     #[test]
@@ -318,6 +322,16 @@ mod tests {
     fn transpose_identity() {
         let mut m = Matrix::identity();
         m.transpose();
-        assert_eq!(m, Matrix::<4>::identity());
+        assert_eq!(m, Matrix::<4, 4>::identity());
+    }
+
+    #[test]
+    fn determinant_2x2() {
+        let m = Matrix::from_array([
+            [1.0, 5.0],
+            [-3.0, 2.0],
+        ]);
+
+        assert_eq!(17.0, m.determinant());
     }
 }