[Haskell-cafe] Problem with own written monad
miguelimo38 at yandex.ru
Mon Jan 7 14:19:48 EST 2008
>> Yes. It's simply impossible. The Stack data type can't be turned
>> into a monad.
> Why not? Surely this is just a variation on the theme of a state
Because it can't be turned into a functor. You can't, given a
function a -> b, construct a function Stack a -> Stack b. On the
contrast, you can easily construct a function State z a -> State z b.
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