procedure dunpack2(var vv: vtuple; var v1,v2: vector);
var
  i: integer;
  vt0,vt1,vt2: vector;
begin { dunpack2 }
  vsprod(v1[0],vv[0],vt0);
  for i:=1 to 3 do begin
    vsprod(v1[i],vv[i],vt1);
    vsum(vt0,vt1,vt2);
    vt0:=vt2;
  end;
  vdiff(v1,vt0,v2);
  for i:=0 to 3 do szero(v2[i]);
end { dunpack2 };

