DEFINITION MODULE NRMatr;

  (* EXPORT QUALIFIED Matrix, PtrToLine, PtrToLines, NilMatrix, EmptyMatrix,
                      EmptyMatrix, CreateMatrix, DisposeMatrix, DimensionsOfMatrix,
                      MatrixPtr, GetMatrixAttr, SetElement, GetElement; *)

   CONST
      MaxNM = 1000;
   TYPE
      Matrix;
      PtrToLine  = POINTER TO ARRAY [0..MaxNM-1] OF REAL;
      PtrToLines = POINTER TO ARRAY [0..MaxNM-1] OF PtrToLine;
   VAR
      NilMatrix: Matrix;

   PROCEDURE EmptyMatrix(n, m: INTEGER): Matrix;

      (* 
       * It creates a new matrix of real numbers with line number n and column 
       * number m if n, m > 0. Otherwise it returns NilMatrix.
       * The elements in the matrix are undefined.
       *)

   PROCEDURE CreateMatrix(    n, 
                              m: INTEGER;
                          VAR matrix: Matrix;
                          VAR lines: PtrToLines);
      (* 
       * It creates a new matrix with n lines and m columns, if n, m > 0.  
       * It returns the reference variable "matrix" and a pointer to the lines
       * of the matrix. If n = 0 and m = 0, then matrix = NilMatrix, lines = NIL.
       * The elements in the matrix are undefined.
       *)

   PROCEDURE DisposeMatrix(VAR matrix: Matrix);

      (*
       * The input "matrix" is deallocated. 
       * Output: "matrix"=NilMatrix.
       * Use this procedure only for matrices created before!
       *)

   PROCEDURE DimensionsOfMatrix(    matrix: Matrix;
                                VAR n, m:   INTEGER);

      (* 
       * It returns the number of lines and columns of matrix.
       *)

   PROCEDURE MatrixPtr(matrix: Matrix): PtrToLines;

      (* 
       * This procedure returns a pointer to the lines of matrix.
       *)

   PROCEDURE GetMatrixAttr(    matrix: Matrix;
                           VAR n, m:   INTEGER;
                           VAR lines:  PtrToLines);
      (* 
       * n, m: The number of lines and columns of matrix;
       * lines: Pointer to the lines of the matrix.
       *)

   PROCEDURE SetElement(matrix: Matrix;
                        i, j:   INTEGER;
                        number: REAL);
      (* 
       * Sets the element with index i, j of the matrix to number.
       *)

   PROCEDURE GetElement(    matrix: Matrix;
                            i, j:   INTEGER;
                        VAR number: REAL);
      (* 
       * Gets the element with index i, j of the matrix in the variable number.
       *)

END NRMatr.