ds020.hs:8:1:
    Warning: Pattern match(es) are overlapped
             In an equation for `a': a ~(~[], ~[], ~[]) = ...

ds020.hs:11:1:
    Warning: Pattern match(es) are overlapped
             In an equation for `b': b ~(~x : ~xs : ~ys) = ...

ds020.hs:16:1:
    Warning: Pattern match(es) are overlapped
             In an equation for `d':
                 d ~(n+43) = ...
                 d ~(n+999) = ...

ds020.hs:22:1:
    Warning: Pattern match(es) are overlapped
             In an equation for `f': f x@(~[]) = ...