List in Prolog with elements in round brackets

Question

Good Morning

I have list similiar to this: [(1-4), (2-4), (3-4)]. I'd like to write only first/second/third part of round bracket. I wrote a function:

write_list([]).

write_list([Head|Tail]) :-
  write(Head), nl,
  write_list(Tail).

It only writes whole round bracket:
1-4
2-4
3-4

I'd like my output to be the 1st element of round bracket:
1
2
3

I'll be grateful for any help :D

Answer 1

Here you are:

write_list([]).
write_list([(A-_)|Tail]) :-
  writeln(A),
  write_list(Tail).

Query:

?- write_list([(1-4),(2-4),(3-4)]).
1
2
3
true

writeln/1 is simply write/1 followed by nl .