microbit-dal/inc/Matrix4.h

#ifndef MICROBIT_MATRIX4_H
#define MICROBIT_MATRIX4_H

/**
* Class definition for a simple matrix, that is optimised for nx4 or 4xn matrices.
*
* This class is heavily optimised for these commonly used matrices as used in 3D geometry.
* Whilst this class does support basic operations on matrices of any dimension, it is not intended as a
* general purpose matrix class as inversion operations are only provided for 4x4 matrices.
* For programmers needing more flexible Matrix support, the Matrix and MatrixMath classes from
* Ernsesto Palacios provide a good basis:
*
* https://developer.mbed.org/cookbook/MatrixClass
* https://developer.mbed.org/users/Yo_Robot/code/MatrixMath/
*/
class Matrix4
{
	float   *data;         // Linear buffer representing the matrix.
	int     rows;           // The number of rows in the matrix.
	int     cols;           // The number of columns in the matrix.

public:

	/**
	* Constructor.
	* Create a matrix of the given size.
	* @param rows the number of rows in the matrix to be created.
	* @param cols the number of columns in the matrix to be created.
	*
	* Example:
	* @code
	* Matrix4(10, 4);        // Creates a Matrix with 10 rows and 4 columns.
	* @endcode
	*/
	Matrix4(int rows, int cols);

	/**
	* Constructor.
	* Create a matrix that is an identical copy of the given matrix.
	* @param matrix The matrix to copy.
	*
	* Example:
	* @code
	*
	* Matrix newMatrix(matrix);        .
	* @endcode
	*/
	Matrix4(const Matrix4 &matrix);

	/**
	* Determines the number of columns in this matrix.
	*
	* @return The number of columns in the matrix.
	*
	* Example:
	* @code
	* int c = matrix.width();
	* @endcode
	*/
	int width();

	/**
	* Determines the number of rows in this matrix.
	*
	* @return The number of rows in the matrix.
	*
	* Example:
	* @code
	* int r = matrix.height();
	* @endcode
	*/
	int height();

	/**
	* Reads the matrix element at the given position.
	*
	* @param row The row of the element to read
	* @param col The column of the element to read
	* @return The value of the matrix element at the given position. NAN is returned if the given index is out of range.
	*
	* Example:
	* @code
	* float v = matrix.get(1,2);
	* @endcode
	*/
	float get(int row, int col);

	/**
	* Writes the matrix element at the given position.
	*
	* @param row The row of the element to write
	* @param col The column of the element to write
	* @param v The new value of the element
	*
	* Example:
	* @code
	* matrix.set(1,2,42.0);
	* @endcode
	*/
	void set(int row, int col, float v);

	/**
	* Transposes this matrix.
	* @return the resultant matrix.
	*
	* Example:
	* @code
	* matrix.transpose();
	* @endcode
	*/
	Matrix4 transpose();

	/**
	* Multiplies this matrix with the given matrix (if possible).
	* @return the resultant matrix. An empty matrix is returned if the operation canot be completed.
	*
	* Example:
	* @code
	* Matrix result = matrixA.multiply(matrixB);
	* @endcode
	*/
	Matrix4 multiply(Matrix4 &matrix, bool transpose = false);

	/**
	* Multiplies the transpose of this matrix with the given matrix (if possible).
	* @return the resultant matrix. An empty matrix is returned if the operation canot be completed.
	*
	* Example:
	* @code
	* Matrix result = matrixA.multiplyT(matrixB);
	* @endcode
	*/
	Matrix4 multiplyT(Matrix4 &matrix);

	/**
	* Performs an optimisaed inversion of a 4x4 matrix.
	* Only 4x4 matrics are supported by this operation.
	*
	* @return the resultant matrix. An empty matrix is returned if the operation canot be completed.
	*
	* Example:
	* @code
	* Matrix result = matrixA.invert();
	* @endcode
	*/
	Matrix4 invert();

	/**
	* Destructor.
	*/
	~Matrix4();
};

inline Matrix4 Matrix4::multiplyT(Matrix4 &matrix)
{
    return multiply(matrix, true);
}

#endif