Wondering if as a practical matter the post-compilation of the second solution below is more efficient .
first solution :
write_data([]).
write_data([_]) :-
write('LAST!'),nl.
write_data([X|Rest]) :-
Rest = [_|_],
write(X),nl,
write_data(Rest).
second solution :
write_data([]).
write_data([H|T]) :-
write_data(T, H).
write_data([], _) :-
write('LAST!'),nl.
write_data([H|T], X) :-
write(X),nl,
write_data(T, H).
some swipl magic :
?- [library(vm)] .
?- vm_list(write_data) , halt.
first solution swipl magic ::
========================================================================
write_data/1
========================================================================
0 s_virgin
1 i_exit
----------------------------------------
clause 1 (<clause>(0xb002c300)):
----------------------------------------
0 h_nil
1 i_exitfact
----------------------------------------
clause 2 (<clause>(0xb017da50)):
----------------------------------------
0 h_list
1 h_void
2 h_nil
3 h_pop
4 i_enter
5 b_atom('LAST!')
7 i_call(write/1)
9 i_depart(nl/0)
11 i_exit
----------------------------------------
clause 3 (<clause>(0xb002bc80)):
----------------------------------------
0 h_list_ff(1,2)
3 i_enter
4 b_unify_var(2)
6 h_list
7 h_pop
8 b_unify_exit
9 b_var1
10 i_call(write/1)
12 i_call(nl/0)
14 b_var2
15 i_depart(write_data/1)
17 i_exit
second solution swipl magic ::
========================================================================
write_data/1
========================================================================
0 s_virgin
1 i_exit
----------------------------------------
clause 1 (<clause>(0xb272c300)):
----------------------------------------
0 h_nil
1 i_exitfact
----------------------------------------
clause 2 (<clause>(0xb27288c0)):
----------------------------------------
0 h_list_ff(1,2)
3 i_enter
4 b_var2
5 b_var1
6 i_depart(write_data/2)
8 i_exit
========================================================================
write_data/2
========================================================================
0 s_virgin
1 i_exit
----------------------------------------
clause 1 (<clause>(0xb2728920)):
----------------------------------------
0 h_nil
1 i_enter
2 b_atom('LAST!')
4 i_call(write/1)
6 i_depart(nl/0)
8 i_exit
----------------------------------------
clause 2 (<clause>(0xb272bc80)):
----------------------------------------
0 h_list_ff(2,3)
3 i_enter
4 b_var1
5 i_call(write/1)
7 i_call(nl/0)
9 b_var(3)
11 b_var2
12 i_depart(write_data/2)
14 i_exit
Upon submission of the above stack overflow blocked with message "It looks like your post is mostly code; please add some more details." . HRM . Too much code in a question about computer programming ? (skratches virtual head) . Should I add some verbiage I heard about the new revolution "Bunch-Oriented" programming whilst around the water-cooler ?