From ac8c70d5a413e26693069b60bb5365b21afcd556 Mon Sep 17 00:00:00 2001
From: Quinn <quinn.henthorne@gmail.com>
Date: Mon, 9 Dec 2024 17:48:50 -0500
Subject: [PATCH] Started working on the matrix library

---
 Matrix.h   | 203 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 Vector3D.h |   1 +
 2 files changed, 204 insertions(+)
 create mode 100644 Matrix.h

diff --git a/Matrix.h b/Matrix.h
new file mode 100644
index 0000000..5ef8848
--- /dev/null
+++ b/Matrix.h
@@ -0,0 +1,203 @@
+#include <cstdint>
+#include <array>
+#include <type_traits>
+
+template <uint8_t rows, uint8_t columns>
+class Matrix{
+    public:
+    /**
+     * @brief Element-wise matrix addition
+     * @param other the other matrix to add to this one
+     * @param result A buffer to store the result into
+     */
+    void Add(const Matrix<rows, columns> & other, Matrix<rows, columns> & result) const;
+    
+    /**
+     * @brief Element-wise subtract matrix
+     * @param other the other matrix to subtract from this one
+     * @param result A buffer to store the result into
+     */
+    void Subtract(const Matrix<rows, columns> & other, Matrix<rows, columns> & result) const;
+
+    /**
+     * @brief Matrix multiply the two matrices
+     * @param other the other matrix to multiply into this one
+     * @param result A buffer to store the result into
+     */
+    template <uint8_t other_columns>
+    void Multiply(const Matrix<rows, columns> & other, Matrix<columns, other_columns> & result) const;
+    
+    /**
+     * @brief Multiply the matrix by a scalar
+     * @param scalar the the scalar to multiply by
+     * @param result A buffer to store the result into
+     */
+    void Multiply(float scalar, Matrix<rows, columns> & result) const;
+    
+    /**
+     * @brief Invert this matrix
+     * @param result A buffer to store the result into
+     */
+    void Invert(Matrix<rows, columns> & result) const;
+
+    /**
+     * @brief Transpose this matrix
+     * @param result A buffer to store the result into
+     */
+    void Transpose(Matrix<columns, rows> & result) const;
+
+    /**
+     * @brief Square this matrix
+     * @param result A buffer to store the result into
+     */
+    void Square(Matrix<rows, columns> & result) const;
+
+    /**
+     * @return Get the determinant of the matrix
+     */
+    float Det();
+
+    /**
+     * @brief Element-wise multiply the two matrices
+     * @param other the other matrix to multiply into this one
+     * @param result A buffer to store the result into
+     */
+    void ElementMultiply(const Matrix<rows, columns> & other, Matrix<rows, columns> & result) const;
+
+    /**
+     * @brief Element-wise divide the two matrices
+     * @param other the other matrix to multiply into this one
+     * @param result A buffer to store the result into
+     */
+    void ElementDivide(const Matrix<rows, columns> & other, Matrix<rows, columns> & result) const;
+    
+    /**
+     * @brief Get an element from the matrix
+     * @param row the row index of the element
+     * @param column the column index of the element
+     * @return The value of the element you want to get
+     */
+    float & Get(uint8_t row_index, uint8_t column_index) const;
+
+    /**
+     * @brief Get a row from the matrix
+     * @param row_index the row index to get
+     * @param row a buffer to write the row into
+     */
+    void GetRow(uint8_t row_index, Matrix<rows, 1> & row) const;
+
+    /**
+     * @brief Get a row from the matrix
+     * @param column_index the row index to get
+     * @param column a buffer to write the row into
+     */
+    void GetColumn(uint8_t column_index, Matrix<1, columns> & column) const;
+
+    /**
+     * @brief Get the number of rows in this matrix
+     */
+    constexpr uint8_t GetRowSize(){return rows;}
+
+    /**
+     * @brief Get the number of columns in this matrix
+     */
+    constexpr uint8_t GetColumnSize(){return columns;}
+
+    private:
+
+    /**
+     * @brief take the dot product of the two vectors
+     */
+    template <uint8_t vector_size>
+    float dotProduct(const Matrix<vector_size, 1> & vec1, const Matrix<vector_size, 1> & vec2);
+    
+    /**
+     * @brief Set all elements in this matrix to zero
+     */
+    void zeroMatrix();
+
+    void matrixOfMinors(const Matrix<rows, columns> & input, Matrix<rows, columns> & result) const;
+
+    void adjugate(const Matrix<rows, columns> & input, Matrix<rows, columns> & result) const;
+
+    std::array<std::array<float, columns>, rows> matrix;
+};
+
+template <uint8_t rows, uint8_t columns>
+void Matrix<rows, columns>::Add(const Matrix<rows, columns> & other, Matrix<rows, columns> & result) const{
+    for(uint8_t row{0}; row < rows; row++){
+        for(uint8_t column{0}; column < columns; column++){
+            result.Get(row, column) = this->Get(row, column) + other.Get(row, column);
+        }
+    }
+}
+
+template <uint8_t rows, uint8_t columns>
+void Matrix<rows, columns>::Subtract(const Matrix<rows, columns> & other, Matrix<rows, columns> & result) const{
+    for(uint8_t row{0}; row < rows; row++){
+        for(uint8_t column{0}; column < columns; column++){
+            result.Get(row, column) = this->Get(row, column) - other.Get(row, column);
+        }
+    }
+}
+
+template <uint8_t rows, uint8_t columns>
+template <uint8_t other_columns>
+void Matrix<rows, columns>::Multiply(const Matrix<rows, columns> & other, Matrix<columns, other_columns> & result) const{
+    for(uint8_t row_idx{0}; row_idx < rows; row_idx++){
+        for(uint8_t column_idx{0}; column_idx < columns; column_idx++){
+            // get our row
+            Matrix<rows, 1> this_row;
+            this->GetRow(row_idx, this_row);
+            // get the other matrices column
+            Matrix<1, columns> other_column;
+            other.GetColumn(column_idx, other_column);
+            // transpose the other matrix's column
+            Matrix<columns, 1> other_column_t;
+            other_column.Transpose(other_column_t);
+
+            // the result's index is equal to the dot product of these two vectors
+            result.Get(row_idx, column_idx) = this->dotProduct(this_row, other_column_t);
+        }
+    }
+}
+
+template <uint8_t rows, uint8_t columns>
+void Matrix<rows, columns>::Multiply(float scalar, Matrix<rows, columns> & result) const{
+    for(uint8_t row_idx{0}; row_idx < rows; row_idx++){
+        for(uint8_t column_idx{0}; column_idx < columns; column_idx++){
+            result.Get(row_idx, column_idx) = this->Get(row_idx, column_idx) * scalar;
+        }
+    }
+}
+
+template <uint8_t rows, uint8_t columns>
+void Matrix<rows, columns>::Invert(Matrix<rows, columns> & result) const{
+    // since all matrix sizes have to be statically specified at compile time we can do this
+    static_assert(rows == columns, "Your matrix isn't square and can't be inverted");
+
+    // unfortunately we can't calculate this at compile time so we'll just reurn zeros
+    if(this->Det() < 0){
+        // you can't invert a matrix with a negative determinant
+        result.zeroMatrix();
+        return;
+    }
+
+    // how to calculate the inverse: https://www.mathsisfun.com/algebra/matrix-inverse-minors-cofactors-adjugate.html
+
+    // calculate the matrix of minors
+    Matrix<rows, columns> minors{};
+    this->matrixOfMinors(this, minors);
+
+    // now adjugate the matrix and save it in our output
+    this->adjugate(minors, result);
+    float determinant = this->Det();
+
+    // scale the result by 1/determinant and we have our answer
+    result.Multiply(1/determinant);
+}
+
+template <uint8_t rows, uint8_t columns>
+void Matrix<rows, columns>::Transpose(Matrix<columns, rows> & result) const{
+
+}
\ No newline at end of file
diff --git a/Vector3D.h b/Vector3D.h
index cb60300..f625f16 100644
--- a/Vector3D.h
+++ b/Vector3D.h
@@ -2,6 +2,7 @@
 
 #include <cstdint>
 #include <cmath>
+#include <type_traits>
 
 template <typename Type>
 class V3D{