% Figure 19.5  Problem definition for learning list membership.


% Problem definition for learning about member(X,L)

backliteral( member(X,L), [L:list], [X:item] ).  % Background literal

% Refinement of terms

term( list, [X|L], [ X:item, L:list]).
term( list, [], []).

prolog_predicate( fail).          % No background predicate in Prolog

start_clause( [ member(X,L) ] / [ X:item, L:list] ).

% Positive and negative examples

ex( member( a, [a])).
ex( member( b, [a,b])).
ex( member( d, [a,b,c,d,e])).

nex( member( b, [a])).
nex( member( d, [a,b])).
nex( member( f, [a,b,c,d,e])).