PROCEDURE Shellsort(VAR A : ScalarTyp;
			n : INDEX);
{
The array A[1..n] is sorted in ascending order. The method is that
of D.A. Shell, (A high-speed sorting procedure, Comm. ACM 2 (1959),
30-32) with subsequences chosen as suggested by T.N. Hibberd.
}
VAR
  i, j, k, m	: integer;
  done 		: BOOLEAN;
  temp		: SCALAR;
begin (*$C-,M-,F-*)
  m := n;
  While m <> 0 do
    begin
      m := m DIV 2;
      k := n - m;
      for j:=1 to k do
	begin
	  i := j;
	  done := FALSE;
	  repeat
	    if A[i+m] >= A[i] then
	      done := TRUE
	    else
	      begin
		temp := A[i]; A[i] := A[i+m]; A[i+m] := temp;
		i := i - m;
	      end;
	  until (i<1) OR ( done );
	end{for j};
    end{While};
end;{Shellsort}{$C+,M+,F+}