Question

Write a Prolog program called replace that replaces all occurrences of one item in a list with a new item. Example under:

?- replace([apple,butter,apple,candy,apple,potato],apple,milk,Result).

Result = [milk,butter,milk,candy,milk,potato]

Answer 1

PREDICATE IN PROLOG:

replace([], _, _, []). %base case for empty list
%recursive cases
%when first element of list is to be replaced, we replace it and recurse for rest of list
replace([X1|Y1], X1, X2, [X2|Y2]):- replace(Y1, X1, X2, Y2), !.
%when first element of list is not to be replaced, we keep it and recurse for rest of list
replace([X|Y1], X1, X2, [X|Y2]):- replace(Y1, X1, X2, Y2).

OUTPUT:

Regards!