Maybe it is because deleteBy is defined wrongly? i.e. it is not logical, doesn't follow the common sense user might expect. It accepts any predicate but narrows requirements only in docs. Maybe best could be to just take a value for comparison and use "==" against it? ("overloaded" or "built-in" (I'm a C++ engineer but as I know it is possible in Haskell as well.)) And to have separate delete which accepts arbitrary predicate. (As it is now.) Regards, Zura Albert Y. C. Lai wrote:
The doc of deleteBy states: "The deleteBy function behaves like delete, but takes a user-supplied equality predicate." A precondition is that the user-supplied predicate is an equality predicate. (>=) is not an equality predicate, be it in the layperson sense of "it isn't analogous to (==)" or the mathematical sense of "it isn't an equivalence relation".
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