Category : Pascal Source Code
Archive   : USNGTP.ZIP
Filename : LST04-02.PAS

(* Include the following directive if code is being compiled on
an 8 bit CP/M system.
{$A-}
*)
procedure Sort_List(var values: Word_Array; lo, hi: Integer);
var new_lo,
new_hi : Integer; { Used to divide the array of values.}
center_value,
hold_value : Word_Str; { Used when values are swaped.}

begin
if ((hi - lo) > 1) then
begin
center_value := values[(hi + lo) div 2];
new_lo := lo; new_hi := hi;
while (new_lo <= new_hi) do
begin
while(values[new_lo] < center_value) do
new_lo := Succ(new_lo);
while(values[new_hi] > center_value) do
new_hi := Pred(new_hi);
if (new_lo <= new_hi) then
begin
hold_value := values[new_lo];
values[new_lo] := values[new_hi];
values[new_hi] := hold_value;
new_lo := Succ(new_lo);
new_hi := Pred(new_hi);

end; {if}
end; {while}
Sort_List(values,lo,new_hi);
Sort_List(values,new_lo,hi);
end
else
if ((hi - lo) = 1) then
if (values[hi] < values[lo]) then
begin
hold_value := values[hi];
values[hi] := values[lo];
values[lo] := hold_value;
end;
end; { Sort_List }

(* Include the following directive if code is being compiled on
an 8 bit CP/M system.
{$A+}
*)

{ Listing. 4-2 Sort_List procedure using the quicksort
algorithm.
}