:- module(uutil, [
		   op(800,fy, $),
   		   ($)/1, ($)//1,
   		   (^)/3, (^)/4,
   		   seq//1, seqq//1, (...)//0
   		 ]).


:- meta_predicate ^(?,0,?).
^(Xs, Goal, Xs) :- call(Goal).
:- meta_predicate ^(?,1,?,?).
^(Xs0, Goal, Xs0, Xs) :- call(Goal, Xs).

... --> [] | [_], ... .

seq([]) --> [].
seq([E|Es]) --> [E], seq(Es).

seqq([]) --> [].
seqq([Es|Ess]) --> seq(Es), seqq(Ess).

:- op(950,fy, [$]).
$(X) :-
	  copy_term_nat(X,Y),numbervars(Y,0,_),portray_clause(call:Y),
	  X,
	  copy_term_nat(X,Z),numbervars(Z,0,_),portray_clause(exit:Z).
%$(X) :-
%	  copy_term_nat(X,Y),numbervars(Y,0,_),portray_clause(fail:Y),
%	  fail.