-- sparse.ads     Sparse storage of a matrix
--                specifically designed for solving PDE
--                simultaneous equations.
--                zero based subscripting
--                column (nrow) is right hand side
--
--      with real_arrays;
--      use real-arrays;
--      package A is new sparse(nrow);
--      use A;
--      i,j:integer;
--      val:real;
--      A.put(i,j,val);

with Real_Arrays;
use Real_Arrays;

generic
  Nrow : Integer;
package Sparse is
  procedure Put(I : Integer; J : Integer; Val : Real);
  procedure Add(I : Integer; J : Integer; Val :Real);
  procedure Simeq(X : out Real_Vector); -- X returned solution
  procedure Multiply(X : in Real_Vector; Y : out Real_Vector);
  procedure Import(M : in Real_Matrix);
  procedure Export(M : out Real_Matrix);
  procedure Clear;
  function  Get(I : Integer; J : Integer) return Real;
  procedure GetRHS(Y : out Real_Vector);
  procedure SetRHS(Y : in Real_Vector);
  procedure Write_All;
  procedure Divide(Krow : Integer; K : Integer); -- works on a Krow j=k+1..n
  procedure Reduce(Irow : Integer; K : Integer; Krow : Integer);
                   -- works on complete Irow  j=k+1..n
                   -- using Krow j=k+1..n  where it exists
private
  type Cell;
  type Link is access Cell;
  type Cell is
     record
        J : Integer := -1;
        Val : Real := 0.0;
        Next : Link := null;
     end record;
  A : array(0..Nrow-1) of link;
end Sparse;