%Source: https://sites.google.com/site/prologsite/prolog-problems %query:insert_at(g,g,g,f). % P21 (*): Insert an element at a given position into a list % The first element in the list is number 1. % insert_at(X,L,K,R) :- X is inserted into the list L such that it % occupies position K. The result is the list R. % (element,list,integer,list) (?,?,+,?) insert_at(X,L,K,R) :- remove_at(X,R,K,L). remove_at(X,[X|Xs],1,Xs). remove_at(X,[Y|Xs],K,[Y|Ys]) :- K > 1, K1 is K - 1, remove_at(X,Xs,K1,Ys).
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