SWISH -- SWI-Prolog for SHaring

% Student exercise profile
:- set_prolog_flag(occurs_check, error).        % disallow cyclic terms
:- set_prolog_stack(global, limit(8 000 000)).  % limit term space (8Mb)
:- set_prolog_stack(local,  limit(2 000 000)).  % limit environment space

% Your program goes here
:- use_module(library(dcg/basics)).

% S --> e | non_letters, Word, non_letters, S.
% Word --> letter Word | e
s([H|Rest]) --> non_letters, word(H), non_letters, s(Rest).
s([]) --> [].

non_letters --> non_letter, non_letters.
non_letters --> [].

non_letter --> [C], {\+ code_type(C, alpha)}.

word([L|Rest]) --> letter(L), word(Rest).
word([]) --> [].

letter(C) --> [C], {code_type(C, alpha)}.

word_acc(Word) --> letter(L), word_rest([L], Word).

word_rest(Acc, Word) --> letter(L), word_rest([L|Acc], Word).
word_rest(Acc, Out) --> [], {reverse(Acc, Out)}.

%%%%%%%%%%%%%

print_(Out) :-
    nested_list(Out),
    !,
    print_list(Out).

print_(Out) :-
    \+ nested_list(Out),
    !,
    format('~s~n', [Out]).

print_list([]).
print_list([H|Rest]) :-
	print_(H),
	print_list(Rest).

nested_list([H|_]) :- is_list(H).