palin.erl

-module(palin).

-export([server/1]).

% palindrome problem
%
% palindrome("Madam I\'m Adam.") = true
palindrome(Xs) -> palin(nocaps(nopunct(Xs))).

nopunct([]) -> [];
nopunct([X | Xs]) ->
    case lists:member(X, "., ;:\t\n'\"") of
      true -> nopunct(Xs);
      false -> [X | nopunct(Xs)]
    end.

nocaps([]) -> [];
nocaps([X | Xs]) -> [nocap(X) | nocaps(Xs)].

nocap(X) ->
    case $A =< X andalso X =< $Z of
      true -> X + 32;
      false -> X
    end.

% literal palindrome

palin(Xs) -> Xs == reverse(Xs).

reverse(Xs) -> shunt(Xs, []).

shunt([], Ys) -> Ys;
shunt([X | Xs], Ys) -> shunt(Xs, [X | Ys]).

% server(Pid) -> 
    
% end.

result(Pid) ->
    receive
        {check, S} -> 
            case palindrome(S) of
                true -> 
                    Pid ! {result, "\"" ++ S ++ "\" is a palindrome"};
                _false -> 
                    Pid ! {result, "\"" ++ S ++ "\" is not a palindrome"};
        _stop ->
            io:format("stopped~n")
    end
end.