[Haskell-cafe] How do I do conditional tail recursion in a monad?

[David F. Place]

Interesting, but what if 'p' is also a monadic action?  For instance,  
it might access the state of the State monad which 'f' is updating.

On Mar 21, 2007, at 5:31 AM, Jules Bean wrote:

> ..but here 'f' is a pure function, not a monadic action. If you  
> want f to be a monadic action then you want:
>
> *Main> :t let untilM p f x = if p x then return x else untilM p f  
> =<< f x in untilM
> let untilM p f x = if p x then return x else untilM p f =<< f x in  
> untilM :: (Monad m) => (a -> Bool) -> (a -> m a) -> a -> m a

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David F. Place
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