with Standard_Floating_Numbers;          use Standard_Floating_Numbers;
with Standard_Complex_Numbers;           use Standard_Complex_Numbers;
with Standard_Natural_Vectors;
with Standard_Integer_Vectors;
with Standard_Integer_VecVecs;           use Standard_Integer_VecVecs;
with Standard_Complex_Vectors;           use Standard_Complex_Vectors;
with Standard_Complex_Matrices;          use Standard_Complex_Matrices;
with Standard_Complex_Linear_Solvers;    use Standard_Complex_Linear_Solvers;
with Standard_Complex_Laur_Polys;        use Standard_Complex_Laur_Polys;
with Binomial_System_Solvers;            use Binomial_System_Solvers;

package body Fewnomial_System_Solvers is

  function Equal ( v : Standard_Integer_Vectors.Link_to_Vector; d : Degrees ) 
                 return boolean is
  begin
    return Standard_Integer_Vectors.Equal
             (v,Standard_Integer_Vectors.Link_to_Vector(d));
  end Equal;

  function Is_Fewnomial_System ( p : Laur_Sys ) return boolean is

    da : VecVec(p'range);
    nb : natural;
    n : natural := p'last - p'first + 1;
    cnst : Standard_Integer_Vectors.Link_to_Vector;
    res : boolean;

    procedure Scan_Term ( t : in Term; cont : out boolean ) is

      found : boolean;

    begin
      found := false;
      for i in da'range loop
	exit when i > nb;
	if Equal(da(i),t.dg)
	 then found := true;
	      exit;
        end if;
      end loop;
      if not found
       then if nb < n
	     then nb := nb + 1;
		  found := true;
		  da(nb) := new Standard_Integer_Vectors.Vector(t.dg'range);
		  for j in t.dg'range loop
		    da(nb)(j) := t.dg(j);
                  end loop;
             elsif nb < n + 1
		 then nb := nb + 1;
		      cnst := new Standard_Integer_Vectors.Vector(t.dg'range);
		      found := true;
		      for j in t.dg'range loop
			cnst(j) := t.dg(j);
                      end loop;
		 elsif Equal(cnst,t.dg)
		     then found := true;
		     else res := false;
            end if;
      end if;
      cont := found;
    end Scan_Term;
    procedure Scan_Terms is new Visiting_Iterator (Scan_Term);

  begin
    res := true;
    nb := 0;
    for i in p'range loop
      Scan_Terms(p(i));
      exit when not res;
    end loop;
    Clear(da);
    Standard_Integer_Vectors.Clear(cnst);
    return res;
  end Is_Fewnomial_System;

  procedure Scale ( cnst : in Standard_Integer_Vectors.Link_to_Vector;
                    da : in out VecVec ) is

  -- DESCRIPTION :
  --   If cnst is not equal to the zero degrees,
  --   then all entries in da will be shifted along cnst.

    zero : boolean;

  begin
    zero := true;
    for i in cnst'range loop
      if cnst(i) /= 0
       then zero := false; exit;
      end if;
    end loop;
    if not zero
     then for i in da'range loop
	    Standard_Integer_Vectors.Sub(da(i),cnst);
          end loop;
    end if;
  end Scale;

  procedure Initialize ( p : in Laur_Sys; n : in natural;
			 a : in out matrix; b : in out vector;
		         da : in out VecVec; fail : out boolean ) is

  -- DESCRIPTION :
  --   initializes the data needed for the solver;
  --   fail becomes true if the system p has too many different terms.

    cnst : Standard_Integer_Vectors.Link_to_Vector;
    da_numb,cnt : natural;
    fl : boolean;

    use Standard_Integer_Vectors;

    procedure Search_Term ( t : in Term; cont : out boolean ) is

      found : boolean;

    begin
      found := false;
      for i in da'range loop
        exit when i > da_numb;
        if Equal(da(i),t.dg)
         then found := true;
              a(cnt,i) := t.cf;
              exit;
        end if;
      end loop;
      if not found
       then
         if da_numb < n
          then da_numb := da_numb + 1;
               da(da_numb) := new Standard_Integer_Vectors.Vector(t.dg'range);
               for k in da(da_numb)'range loop
                 da(da_numb)(k) := t.dg(k);
               end loop;
               found := true;
               a(cnt,da_numb) := t.cf;
          elsif da_numb < n+1
              then da_numb := da_numb + 1;
	           cnst := new Standard_Integer_Vectors.Vector(t.dg'range);
	           for k in cnst'range loop
                     cnst(k) := t.dg(k);
                   end loop;
                   found := true;
                   b(cnt) := -t.cf;
              elsif Equal(cnst,t.dg)
                  then found := true;
                       b(cnt) := -t.cf;
         end if;
      end if;
      if not found
       then cont := false;
	    fl := true;
       else cont := true;
	    fl := false;
      end if;
    end Search_Term;
    procedure Search is new Visiting_Iterator(Search_Term);

  begin
    da_numb := 0;
    for i in p'range loop
      for j in a'range(2) loop
	a(i,j) := Create(0.0);
      end loop;
      b(i) := Create(0.0);
      cnt := i;
      Search(p(i));
      exit when fl;
    end loop;
    if not fl and then (cnst /= null)
     then Scale(cnst,da);
	  Standard_Integer_Vectors.Clear(cnst);
	  fail := false;
     else fail := true;
    end if;
  end Initialize;

  procedure Solve ( p : in Laur_Sys; sols : in out Solution_List;
		    fail : out boolean ) is

    n : natural := p'length;
    da : VecVec(p'range);
    a : Matrix(1..n,1..n);
    b : Vector(1..n);
    fl : boolean;

  begin
    Initialize(p,n,a,b,da,fl);
    if fl
     then fail := true;
     else fail := false;
	  declare
	    piv : Standard_Natural_Vectors.Vector(1..n);
	    info : integer;
          begin
	    lufac(a,n,piv,info);
            if info = 0
	     then lusolve(a,n,piv,b);
		  fl := false;
		  for i in b'range loop
		    if AbsVal(b(i)) + 1.0 = 1.0
		     then fl := true;
			  exit;
                    end if;
                  end loop;
		  if not fl
                   then Solve(da,b,n,sols);
                  end if;
            end if;
          end;
    end if;
    Clear(da);
  end Solve;

end Fewnomial_System_Solvers;