%query: parse(i,o). %TWTYPES :- type parse(list,symbol). parse(Xs,T) :- app(As,[a,s(A,B,C),b|Bs],Xs), app(As,[s(a,s(A,B,C),b)|Bs],Ys), parse(Ys,T). parse(Xs,T) :- app(As,[a,s(A,B),b|Bs],Xs), app(As,[s(a,s(A,B),b)|Bs],Ys), parse(Ys,T). parse(Xs,T) :- app(As,[a,b|Bs],Xs), app(As,[s(a,b)|Bs],Ys), parse(Ys,T). parse([s(A,B)],s(A,B)). parse([s(A,B,C)],s(A,B,C)). %TWTYPES :- type app(list,list,list). app([],X,X). app([X|Xs],Ys,[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)). */
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