Simple question

From: Paul (paul_nospam_at_laberg.com.au)
Date: 02/15/04

  • Next message: Bart Demoen: "Re: Simple question" 
    Date: Sun, 15 Feb 2004 11:14:39 +1100

    Using SWI-Prolog, my program reads as follows...
    *************
    basicpart(rim). basicpart(rearframe). basicpart(gears). basicpart(nut).
    basicpart(spoke). basicpart(handles). basicpart(bolt). 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]).

    partsof(X,[X]) :- basicpart(X).
    partsof(X,P) :-
     assembly(X,Subparts),
     partsoflist(Subparts,P).

    partsoflist([P|Tail],Total) :-
     partsof(P,Headparts),
     partsoflist(Tail,Tailparts),
     append(Headparts,Tailparts,Total).
    *************
    I try and test the progam with :
    partsof(axle,X).
    But it keeps coming back with "No"

    If somebody is feeling really generous perhaps they also can tell me how the
    problem (above) can be seen from the following debug trace:
    [debug] 7 ?- partsof(axle,X).
       Call: (7) partsof(axle, _G490) ? creep
       Call: (8) basicpart(axle) ? creep
       Fail: (8) basicpart(axle) ? creep
       Redo: (7) partsof(axle, _G490) ? creep
       Call: (8) assembly(axle, _L182) ? creep
       Exit: (8) assembly(axle, [bolt, nut]) ? creep
       Call: (8) partsoflist([bolt, nut], _G490) ? creep
       Call: (9) partsof(bolt, _L195) ? creep
       Call: (10) basicpart(bolt) ? creep
       Exit: (10) basicpart(bolt) ? creep
       Exit: (9) partsof(bolt, [bolt]) ? creep
       Call: (9) partsoflist([nut], _L196) ? creep
       Call: (10) partsof(nut, _L233) ? creep
       Call: (11) basicpart(nut) ? creep
       Exit: (11) basicpart(nut) ? creep
       Exit: (10) partsof(nut, [nut]) ? creep
       Call: (10) partsoflist([], _L234) ? creep
       Fail: (10) partsoflist([], _L234) ? creep
       Redo: (10) partsof(nut, _L233) ? creep
       Call: (11) assembly(nut, _L252) ? creep
       Fail: (11) assembly(nut, _L252) ? creep
       Fail: (9) partsoflist([nut], _L196) ? creep
       Redo: (9) partsof(bolt, _L195) ? creep
       Call: (10) assembly(bolt, _L214) ? creep
       Fail: (10) assembly(bolt, _L214) ? creep
       Fail: (8) partsoflist([bolt, nut], _G490) ? creep

    Thanks for the help

  • Next message: Bart Demoen: "Re: Simple question"

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