1 ds020.hs:5: Pattern match(es) are overlapped in the definition of function `a':
2 a ~(~[], ~[], ~[]) = ...
4 ds020.hs:8: Pattern match(es) are overlapped in the definition of function `b':
5 b ~(~x : (~xs : ~ys)) = ...
7 ds020.hs:13: Pattern match(es) are overlapped in the definition of function `d':
11 ds020.hs:19: Pattern match(es) are overlapped in the definition of function `f':