procedure vwrite(f: string; var v: vector);
var
  i: integer;
  t: text;
begin { vwrite }
  write('(vwrite ',trim(f)); flush(output);
  rewrite(t,f);
  writeln(t,vdim);
  for i:=0 to vdim do with v[i] do begin
    writeln(t,rst(l));
    writeln(t,rst(u));
  end;
  flush(t);
  write(')'); flush(output);
end { vwrite };