predicate naming

03_03.pl

basicpart(rim).
basicpart(spoke).
basicpart(rearframe).
basicpart(handles).
basicpart(gears).
basicpart(bolt).
basicpart(nut).
basicpart(fork).

assembly(bike, [wheel, wheel, frame]).
assembly(wheel, [spoke, rim, hub]).
assembly(frame, [rearframe, frontframe]).
assembly(frontframe, [fork, handles]).
assembly(hub, [gears, axle]).
assembly(axle, [bolt, nut]).

% basic predicate
partsof(X,P):-partsacc(X,[],P).

% helper predicate boundary case
partsacc(X,A,[X|A]):-basicpart(X).

% helper predicate
partsacc(X,A,P):-
    assembly(X, Subparts),
    partsacclist(Subparts,A,P).

% worker predicate base case
partsacclist([],A,A).

% worker predicate recursive case
partsacclist([P|Tail], A, Total):-
    partsacc(P,A,Hp),
    partsacclist(Tail, Hp, Total).