Duplicate nth value from list

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Fairly new to Prolog; I'm trying to implement a recursive rule duplicate_nth(N, L1, L2):- which takes a nth value N, a list L1 and duplicates the Nth value of L1 and returns it in a list L2.

Example: querying duplicate_nth(1, [2,3,4], X). should return X = [2,2,3,4].

My current code is:

duplicate_nth(N,[H|T],L2) :-    % N is 1? Append the head of the list to the head and tail of the list
    N = 1,
    append([H],[H|T],L2).

duplicate_nth(N,H|T,L2) :-
    N > 1,

which currently works if N = 1, it will not however work if N > 1 and I am unsure of how to proceed.

edited 28 secs ago

false

8,390

asked 1 min ago

Michael

262