2 ds051.hs:6: Warning: Pattern match(es) are overlapped
3 In the definition of `f1': f1 "ab" = ...
5 ds051.hs:11: Warning: Pattern match(es) are overlapped
6 In the definition of `f2': f2 ('a' : ('b' : [])) = ...
8 ds051.hs:16: Warning: Pattern match(es) are overlapped
9 In the definition of `f3': f3 "ab" = ...