% Reference 9.1: reusable string built-ins cover empty results and scalar list items.
%% goal: answer(X0, X1)

answer(split_missing_separator, X) :- split("abc", ",", X).
answer(split_empty_separator, X) :- split("abc", "", X).
answer(join_empty, X) :- join([], ",", X).
answer(join_numbers, X) :- join([1, 2, 3], "-", X).
answer(substring_empty, X) :- substring("abcdef", 2, 0, X).
answer(replace_empty_search, X) :- replace("abc", "", "x", X).
answer(lower_string, X) :- lowercase("Hello", X).
answer(upper_string, X) :- uppercase("Eyepl 123", X).