如何将 Maybe 值注入 MaybeT
假设我有一些 foo :: Maybe Int 并且我想将它绑定到例如 bar :: Int ->; MaybeT (Writer String) Int，这样做的惯用方法是什么？
我可以定义自己的 liftMaybe 函数，然后使用它，例如：
let liftMaybe = maybe (fail "Nothing") return in liftMaybe foo >>= bar
但是有没有更惯用（或至少简洁）的方法来做到这一点？
Say I have some foo :: Maybe Int and I want to bind it for example with bar :: Int -> MaybeT (Writer String) Int, what would be the idiomatic way to do that?
I could define my own liftMaybe function, and then use that, like:
let liftMaybe = maybe (fail "Nothing") return in liftMaybe foo >>= bar
But is there a more idiomatic (or at least concise) way to do that?
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我认为很遗憾它没有标准名称，但是 a hoogle 搜索，我们看到
relude包使用hoistMaybe：更通用的形式是
优于使用
fail的形式。我只是将它放在某个方便的模块中。I think it's a shame it doesn't have a standard name, however doing a hoogle search, we see that the
reludepackages useshoistMaybe:A more general form is
which is preferable to the use of
fail. I'd just put it in a convenient module somewhere.