member predicate 1

[misoijnr]

hi, help me put this predicate into perspective, was trying to make one to find path on the facts attached.

findpath(Dest,L) :-
find_route(node(NodeID), Dest, L.
findpath(S, Dest, Sol) :-
way(S, Dest, , Path),
invert(Path, Sol).

path( P, P, L, L).
path( Node, Goal, Path, Sol) :-
route( Node, WayID), not( way(WayID) ),
not( member( WayID, Path)),
path( WayID, Goal, [WayID | Path], Sol).

member(X,[X|Xs]).
member(X,[_|Ys]) :- member(X,Ys).

node(NodeID) :- member(NodeID, [lat,long]).
node_tag(NodeID) :- member(NodeID,[name,highway,add:street,crossing,crossing_ref]).
way(WayID) :- member(WayID, Nodelist).
way_tag(WayID):-member(WayID,[name,highway,foot,maxspeed,lanes,oneway,bridge])

 

[misoijnr]

hi kahleen,

i am re-writing the get_path predicate below to take into account iterative deepening also to avoid loop or for loop detection, also, am trying to include lenght as a cost to the search space. however, can i use the edge facts i generated earlier ? check the code below, it tries to analyse paths that have been visited so that it does not loop. advise.

% depth-first search with loop detection
get_path([Path|Rest],Visited,Path):-
path(Path).
get_path([Current|Rest],Visited,Path):-
node(X,Y),
add_path(Y,Rest,Visited,NewPaths),
get_path(NewPaths,[Current|Visited],Path).
add_path([],Paths,Visited,Paths).
add_path([X|Rest],OldPaths,Visited,[X|NewPath]):-
not edge(X,OldPaths),
not edge(X,Visited),
add_path(Rest,OldPaths,Visited,NewPaths).
add_path([X|Rest],OldPaths,Visited,NewPaths):-
edge(X,OldPaths),
add_path(Rest,Oldpaths,Visited,NewPaths).
add_path([X|Rest],OldPaths,Visited,NewPaths):-
edge(X,Visited),
add_path(Rest,OldPaths,Visited,NewPaths).

 

[misoijnr]

how should i avoid singleton variables from the above code, seems am getting that error