% From the book
% PROLOG PROGRAMMING IN DEPTH
% by Michael A. Covington, Donald Nute, and Andre Vellino
% (Prentice Hall, 1997).
% Copyright 1997 Prentice-Hall, Inc.
% For educational use only

% File GETYESNO.PL
% Menu that obtains 'yes' or 'no' answer

get_yes_or_no(Result) :- get(Char),              % read a character
                         get0(_),                % consume the Return after it
                         interpret(Char,Result),
                         !.                      % cut -- see text

get_yes_or_no(Result) :- nl,
                         write('Type Y or N:'),
                         get_yes_or_no(Result).

interpret(89,yes).  % ASCII 89  = 'Y'
interpret(121,yes). % ASCII 121 = 'y'
interpret(78,no).   % ASCII 78  = 'N'
interpret(110,no).  % ASCII 110 = 'n'