How do you append an element to a list in place in Prolog?
If I have a list in Prolog such as X = [1, 2, 3, 4], how do I add the element 5 to the end of the list to have X = [1, 2, 3, 4, 5]?
The append function needs two lists, ie append(A,B,C) to get A and B concatenated to the list C.
I can do this with a temporary list Y = [1, 2, 3, 4] and Z = [5], to then do an append(Y, Z, X), but I don't like having a temporary list.
The usual disclaimers apply here - this is not homework and I am just learning Prolog.
Answer
As the others have pointed out, you're going to be stuck with the performance issue.
But just as an exercise I decided to try and create a predicate that could append an element to the end of a list, without using append.
% add_tail(+List,+Element,-List)
% Add the given element to the end of the list, without using the "append" predicate.
add_tail([],X,[X]).
add_tail([H|T],X,[H|L]):-add_tail(T,X,L).
I would advice that you'd simply use the append function, as a built-in function it is likely to be faster than anything manually crafted.