Reified DCG utils

reif_dcg.pl

:- use_module(library(reif)).

phrase_t(P, I, O, T) :- phrase(call(P, T), I, O).

if_(If, Then, Else, I, O) :-
    if_(phrase_t(If, I, M),
	phrase(Then, M, O),
	phrase(Else, M, O)).

% Example:

eos([], []).

maximal_munch(_) --> eos.
maximal_munch(P) --> if_(P, maximal_munch(P), []).

oneX(X, false), [Y] --> [Y], {dif(X, Y)}.
oneX(X, true) --> [X].

:- phrase(maximal_munch(oneX(a)), _, _).