CODEWITHSUNDEEP
prolog
teo
teo

Reputation: 73

Some help making list of list in prolog

this is my first question here, I'm new in prolog and I'm doing some homework for school.

I have to make a list of lists and I was fighting with these for 2 days now. Maybe some of you can help me.

This is what I have to do:

With an entry of some thing like this:

evaluateList([f(14),_,_,_,_,f(31),_,_],E)

E should be:

E = [14,[_,_,_,_],31,[_,_]]

I have tried to do it, but I cant get the expected result:

evaluateList([],[]).
evaluateList([H|T], [S]) :- var(H), do_vars([H|T],S), !.
evaluateList([f(N)|T],[N|S]) :- evaluateList(T,S), !.

do_vars([],[]).
do_vars([H|T],[H|S]) :- var(H), do_vars(T,S).

After running the code:

evaluateList([f(14),_,_,_,_,f(31),_,_],E)

I'm getting:

E = [14, _1378, _1384, _1390, _1396, 31, [_1414, _1420]]

I mean, I'm getting the 'inside list', but only in the last item.

Any suggestion?

Thank you

Upvotes: 1

Views: 55

Answers (1)

CapelliC
CapelliC

Reputation: 60034

do_vars should 'eat' elements from the list, and return the remainder. So, an additional argument is needed. For instance

evaluateList([],[]).
evaluateList(L,[Vs|T]) :- do_vars(L,Vs,R), Vs\=[], !, evaluateList(R,T).
evaluateList([f(N)|T],[N|S]) :- evaluateList(T,S).

do_vars([V|L],[V|S],R) :- var(V), do_vars(L,S,R).
do_vars(R,[],R).

Upvotes: 1

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