Prolog substitution

Question

How can I replace a list with another list that contain the variable to be replaced. for example

rep([x, d, e, z, x, z, p], [x=z, z=x, d=c], R).
R = [z, c, e, x,         


        

Answer 1

Let's improve this answer by moving the "recursive part" into meta-predicate find_first_in_t/4:

:- meta_predicate find_first_in_t(2,?,?,?).
find_first_in_t(P_2,X,Xs,Truth) :-
   list_first_suchthat_t(Xs,X,P_2,Truth).

list_first_suchthat_t([]    ,_, _ ,false).
list_first_suchthat_t([E|Es],X,P_2,Truth) :-
   if_(call(P_2,E),
       (E=X,Truth=true),
       list_first_suchthat_t(Es,X,P_2,Truth)).

To fill in the "missing bits and pieces", we define key_pair_t/3:

key_pair_t(Key,K-_,Truth) :-
   =(Key,K,Truth).

Based on find_first_in_t/4 and key_pair_t/3, we can write assoc_key_mapped/3 like this:

assoc_key_mapped(Assoc,Key,Value) :-
   if_(find_first_in_t(key_pair_t(Key),_-Value,Assoc),
       true,
       Key=Value).

So, does the OP's use-case still work?

?- maplist(assoc_key_mapped([x-z,z-x,d-c]), [x,d,e,z,a,z,p], Rs).
Rs = [z,c,e,x,a,x,p].                            % OK. same result as before

---

Building on find_first_in_t/4

memberd_t(X,Xs,Truth) :-                        % memberd_t/3
   find_first_in_t(=(X),_,Xs,Truth).

:- meta_predicate exists_in_t(2,?,?).           % exists_in_t/3
exists_in_t(P_2,Xs,Truth) :-
   find_first_in_t(P_2,_,Xs,Truth).