reactphysics3d/src/mathematics/Matrix2x2.h

/********************************************************************************
* ReactPhysics3D physics library, http://code.google.com/p/reactphysics3d/      *
* Copyright (c) 2010-2013 Daniel Chappuis                                       *
*********************************************************************************
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*    appreciated but is not required.                                           *
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#ifndef REACTPHYSICS3D_MATRIX2X2_H
#define REACTPHYSICS3D_MATRIX2X2_H

// Libraries
#include <cassert>
#include "Vector2.h"

/// ReactPhysics3D namespace
namespace reactphysics3d {

// Class Matrix2x2
/**
 * This class represents a 2x2 matrix.
 */
class Matrix2x2 {

    private :

        // -------------------- Attributes -------------------- //

        /// Rows of the matrix;
        Vector2 mRows[3];

    public :

        // -------------------- Methods -------------------- //

        /// Constructor
        Matrix2x2();

        /// Constructor
        Matrix2x2(decimal value);

        /// Constructor
        Matrix2x2(decimal a1, decimal a2, decimal b1, decimal b2);

        /// Destructor
        ~Matrix2x2();

        /// Copy-constructor
        Matrix2x2(const Matrix2x2& matrix);

        /// Assignment operator
        Matrix2x2& operator=(const Matrix2x2& matrix);

        /// Set all the values in the matrix
        void setAllValues(decimal a1, decimal a2, decimal b1, decimal b2);

        /// Set the matrix to zero
        void setToZero();

        /// Return a column
        Vector2 getColumn(int i) const;

        /// Return a row
        Vector2 getRow(int i) const;

        /// Return the transpose matrix
        Matrix2x2 getTranspose() const;

        /// Return the determinant of the matrix
        decimal getDeterminant() const;

        /// Return the trace of the matrix
        decimal getTrace() const;

        /// Return the inverse matrix
        Matrix2x2 getInverse() const;

        /// Return the matrix with absolute values
        Matrix2x2 getAbsoluteMatrix() const;

        /// Set the matrix to the identity matrix
        void setToIdentity();

        /// Return the 2x2 identity matrix
        static Matrix2x2 identity();

        /// Overloaded operator for addition
        friend Matrix2x2 operator+(const Matrix2x2& matrix1, const Matrix2x2& matrix2);

        /// Overloaded operator for substraction
        friend Matrix2x2 operator-(const Matrix2x2& matrix1, const Matrix2x2& matrix2);

        /// Overloaded operator for the negative of the matrix
        friend Matrix2x2 operator-(const Matrix2x2& matrix);

        /// Overloaded operator for multiplication with a number
        friend Matrix2x2 operator*(decimal nb, const Matrix2x2& matrix);

        /// Overloaded operator for multiplication with a matrix
        friend Matrix2x2 operator*(const Matrix2x2& matrix, decimal nb);

        /// Overloaded operator for matrix multiplication
        friend Matrix2x2 operator*(const Matrix2x2& matrix1, const Matrix2x2& matrix2);

        /// Overloaded operator for multiplication with a vector
        friend Vector2 operator*(const Matrix2x2& matrix, const Vector2& vector);

        /// Overloaded operator for equality condition
        bool operator==(const Matrix2x2& matrix) const;

        /// Overloaded operator for the is different condition
        bool operator!= (const Matrix2x2& matrix) const;

        /// Overloaded operator for addition with assignment
        Matrix2x2& operator+=(const Matrix2x2& matrix);

        /// Overloaded operator for substraction with assignment
        Matrix2x2& operator-=(const Matrix2x2& matrix);

        /// Overloaded operator for multiplication with a number with assignment
        Matrix2x2& operator*=(decimal nb);

        /// Overloaded operator to read element of the matrix.
        const Vector2& operator[](int row) const;

        /// Overloaded operator to read/write element of the matrix.
        Vector2& operator[](int row);
};

// Method to set all the values in the matrix
inline void Matrix2x2::setAllValues(decimal a1, decimal a2,
                                    decimal b1, decimal b2) {
    mRows[0][0] = a1; mRows[0][1] = a2;
    mRows[1][0] = b1; mRows[1][1] = b2;
}

// Set the matrix to zero
inline void Matrix2x2::setToZero() {
    mRows[0].setToZero();
    mRows[1].setToZero();
}

// Return a column
inline Vector2 Matrix2x2::getColumn(int i) const {
    assert(i>= 0 && i<2);
    return Vector2(mRows[0][i], mRows[1][i]);
}

// Return a row
inline Vector2 Matrix2x2::getRow(int i) const {
    assert(i>= 0 && i<2);
    return mRows[i];
}

// Return the transpose matrix
inline Matrix2x2 Matrix2x2::getTranspose() const {

    // Return the transpose matrix
    return Matrix2x2(mRows[0][0], mRows[1][0],
                     mRows[0][1], mRows[1][1]);
}

// Return the determinant of the matrix
inline decimal Matrix2x2::getDeterminant() const {

    // Compute and return the determinant of the matrix
    return mRows[0][0] * mRows[1][1] - mRows[1][0] * mRows[0][1];
}

// Return the trace of the matrix
inline decimal Matrix2x2::getTrace() const {

    // Compute and return the trace
    return (mRows[0][0] + mRows[1][1]);
}

// Set the matrix to the identity matrix
inline void Matrix2x2::setToIdentity() {
    mRows[0][0] = 1.0; mRows[0][1] = 0.0;
    mRows[1][0] = 0.0; mRows[1][1] = 1.0;
}

// Return the 2x2 identity matrix
inline Matrix2x2 Matrix2x2::identity() {

    // Return the isdentity matrix
    return Matrix2x2(1.0, 0.0, 0.0, 1.0);
}

// Return the matrix with absolute values
inline Matrix2x2 Matrix2x2::getAbsoluteMatrix() const {
    return Matrix2x2(fabs(mRows[0][0]), fabs(mRows[0][1]),
                     fabs(mRows[1][0]), fabs(mRows[1][1]));
}

// Overloaded operator for addition
inline Matrix2x2 operator+(const Matrix2x2& matrix1, const Matrix2x2& matrix2) {
    return Matrix2x2(matrix1.mRows[0][0] + matrix2.mRows[0][0],
                     matrix1.mRows[0][1] + matrix2.mRows[0][1],
                     matrix1.mRows[1][0] + matrix2.mRows[1][0],
                     matrix1.mRows[1][1] + matrix2.mRows[1][1]);
}

// Overloaded operator for substraction
inline Matrix2x2 operator-(const Matrix2x2& matrix1, const Matrix2x2& matrix2) {
    return Matrix2x2(matrix1.mRows[0][0] - matrix2.mRows[0][0],
                     matrix1.mRows[0][1] - matrix2.mRows[0][1],
                     matrix1.mRows[1][0] - matrix2.mRows[1][0],
                     matrix1.mRows[1][1] - matrix2.mRows[1][1]);
}

// Overloaded operator for the negative of the matrix
inline Matrix2x2 operator-(const Matrix2x2& matrix) {
    return Matrix2x2(-matrix.mRows[0][0], -matrix.mRows[0][1],
                     -matrix.mRows[1][0], -matrix.mRows[1][1]);
}

// Overloaded operator for multiplication with a number
inline Matrix2x2 operator*(decimal nb, const Matrix2x2& matrix) {
    return Matrix2x2(matrix.mRows[0][0] * nb, matrix.mRows[0][1] * nb,
                     matrix.mRows[1][0] * nb, matrix.mRows[1][1] * nb);
}

// Overloaded operator for multiplication with a matrix
inline Matrix2x2 operator*(const Matrix2x2& matrix, decimal nb) {
    return nb * matrix;
}

// Overloaded operator for matrix multiplication
inline Matrix2x2 operator*(const Matrix2x2& matrix1, const Matrix2x2& matrix2) {
    return Matrix2x2(matrix1.mRows[0][0] * matrix2.mRows[0][0] + matrix1.mRows[0][1] *
                     matrix2.mRows[1][0],
                     matrix1.mRows[0][0] * matrix2.mRows[0][1] + matrix1.mRows[0][1] *
                     matrix2.mRows[1][1],
                     matrix1.mRows[1][0] * matrix2.mRows[0][0] + matrix1.mRows[1][1] *
                     matrix2.mRows[1][0],
                     matrix1.mRows[1][0] * matrix2.mRows[0][1] + matrix1.mRows[1][1] *
                     matrix2.mRows[1][1]);
}

// Overloaded operator for multiplication with a vector
inline Vector2 operator*(const Matrix2x2& matrix, const Vector2& vector) {
    return Vector2(matrix.mRows[0][0]*vector.x + matrix.mRows[0][1]*vector.y,
                   matrix.mRows[1][0]*vector.x + matrix.mRows[1][1]*vector.y);
}

// Overloaded operator for equality condition
inline bool Matrix2x2::operator==(const Matrix2x2& matrix) const {
    return (mRows[0][0] == matrix.mRows[0][0] && mRows[0][1] == matrix.mRows[0][1] &&
            mRows[1][0] == matrix.mRows[1][0] && mRows[1][1] == matrix.mRows[1][1]);
}

// Overloaded operator for the is different condition
inline bool Matrix2x2::operator!= (const Matrix2x2& matrix) const {
    return !(*this == matrix);
}

// Overloaded operator for addition with assignment
inline Matrix2x2& Matrix2x2::operator+=(const Matrix2x2& matrix) {
   mRows[0][0] += matrix.mRows[0][0]; mRows[0][1] += matrix.mRows[0][1];
   mRows[1][0] += matrix.mRows[1][0]; mRows[1][1] += matrix.mRows[1][1];
   return *this;
}

// Overloaded operator for substraction with assignment
inline Matrix2x2& Matrix2x2::operator-=(const Matrix2x2& matrix) {
   mRows[0][0] -= matrix.mRows[0][0]; mRows[0][1] -= matrix.mRows[0][1];
   mRows[1][0] -= matrix.mRows[1][0]; mRows[1][1] -= matrix.mRows[1][1];
   return *this;
}

// Overloaded operator for multiplication with a number with assignment
inline Matrix2x2& Matrix2x2::operator*=(decimal nb) {
   mRows[0][0] *= nb; mRows[0][1] *= nb;
   mRows[1][0] *= nb; mRows[1][1] *= nb;
   return *this;
}

// Overloaded operator to return a row of the matrix.
/// This operator is also used to access a matrix value using the syntax
/// matrix[row][col].
inline const Vector2& Matrix2x2::operator[](int row) const {
    return mRows[row];
}

// Overloaded operator to return a row of the matrix.
/// This operator is also used to access a matrix value using the syntax
/// matrix[row][col].
inline Vector2& Matrix2x2::operator[](int row) {
    return mRows[row];
}

}

#endif