+++ /dev/null
-
-tcfail080.hs:11:
- Ambiguous type variable(s) `c' in the constraint `Collection c a'
- arising from use of `singleton' at tcfail080.hs:11
- In the first argument of `isempty', namely `(singleton x)'
- In the right-hand side of an equation for `q':
- isempty (singleton x)