%query: parse(i,o). /* variant of example from toplas collection * using cons and nil instead of [_|_] and [] */ %TWTYPES :- type parse(list,symbol). parse(Xs,T) :- app(As,cons(a,cons(s(A,B,C),cons(b,Bs))),Xs), app(As,cons(s(a,s(A,B,C),b),Bs),Ys), parse(Ys,T). parse(Xs,T) :- app(As,cons(a,cons(s(A,B),cons(b,Bs))),Xs), app(As,cons(s(a,s(A,B),b),Bs),Ys), parse(Ys,T). parse(Xs,T) :- app(As,cons(a,cons(b,Bs)),Xs), app(As,cons(s(a,b),Bs),Ys), parse(Ys,T). parse(cons(s(A,B),nil),s(A,B)). parse(cons(s(A,B,C),nil),s(A,B,C)). %TWTYPES :- type app(list,list,list). app(nil,X,X). app(cons(X,Xs),Ys,cons(X,Zs)) :- app(Xs,Ys,Zs). /*TWDESC bottom-up parser */ /*TWTYPES list([]). list([X|Xs]) :- symbol(X), list(Xs). symbol(a). symbol(b). symbol(s(X,Y)) :- symbol(X), symbol(Y). symbol(s(X,Y,Z)) :- symbol(X), symbol(Y), symbol(Z). */ /*TWDEMO selected_norms([list,symbol]). query(parse(b,f,f,f)). query(app(b,f,f,f,f,f)). query(app(f,b,f,f,f,f)). query(app(f,f,f,f,b,f)). query(app(f,f,f,f,f,b)). */
content may be truncated. 'popout' for larger text window.
