substitute in a nested list (prolog)
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by linda
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Published on 2009-11-20T15:03:30Z
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2010/04/17
22:03 UTC
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/* substitute(X,Y,Xs,Ys) is true if the list Ys is the result of substituting Y for all occurrences of X in the list Xs.
This is what I have so far:
subs(_,_,[],[]).
subs(X,Y,[X|L1],[Y|L2]):- subs(X,Y,L1,L2).
subs(X,Y,[H|L1],[H|L2]):- X\=H, not(H=[_|_]), subs(X,Y,L1,L2).
subs(X,Y,[H|_],[L2]):- X\=H, H=[_|_], subs(X,Y,H,L2).
My code works except it omits the elements following the nested list. For example:
?- subs(a,b,[a,[a,c],a],Z).
Z = [b, [b, c]] .
What should I add to this program?
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