% Thang Le's input routine, Fall 2005
%
%%%% File tokenizer.pl

run(Infile, Outfile) :- readfile(Infile, X), token(Z, X, []), trans(Z, T), !,
  program(T, [], Y), !, open(Outfile, write, S), write(S, Y), close(S).

readfile(In, X) :- atom(In), var(X), open(In, read, S), getfile(S, X), close(S).

writefile(Out, Y) :-
  atom(Out), nonvar(Y), open(Out, write, S), writeq(S, Y), put(S, 46), close(S).

getfile(S, [X|Y]) :- get0(S, X0), (-1==X0 -> Y=[];getfile(S, Y)), changecode(X0, X).

changecode(-1, 32) :- !.
changecode(9, 32) :- !.
changecode(10, 32) :- !.
changecode(X, X).

trans([], []).
trans([=,=|X], [==|Y]) :- trans(X, Y), !.
trans([<,=|X], [<=|Y]) :- trans(X, Y), !.
trans([>,=|X], [>=|Y]) :- trans(X, Y), !.
trans([!,=|X], ['!='|Y]) :- trans(X, Y), !.
trans([H|X], [H|Y]) :- trans(X, Y).

gather(Chars) --> [C], {alphaNumeric(C)}, gather(Rest), {Chars = [C|Rest]}.
gather([]) --> {true}.
alphaNumeric(C) :- 96<C, C<123; 64<C, C<91; 47<C, C<58.
token(Result) --> gather(Chars), {\+(Chars=[])}, token(RestResult),
  {name(N, Chars), Result = [N|RestResult]}.
token(R)--> [C], {C<33}, token(R).
token([N|R]) --> [C], {C>32}, {name(N, [C])}, token(R).
token([]) --> [].