Hi Tony, ​​Take a look at monad-loops package [1]. Seems like you reinvented a version of untilJust [2]. ​​ Your version can be obtained by: yourUntilJust :: (Monad m) => m a -> (a -> Maybe b) -> m byourUntilJust m f = untilJust (liftM f m) Best, Nick [1] <http://hackage.haskell.org/package/monad-loops> http://hackage.haskell.org/package/monad-loops [2] <http://hackage.haskell.org/package/monad-loops-0.4.2/docs/Control-Monad-Loops.html#v:untilJust> http://hackage.haskell.org/package/monad-loops-0.4.2/docs/Control-Monad-Loop... ​ 2013/11/8 Tony Morris <tonymorris@gmail.com>

Hello, I have implemented a function for QuickCheck:

untilJust :: Gen a -> (a -> Maybe b) -> Gen b

I based it on the code for suchThat[1] and suchThatMaybe[2].

I am wondering if I have potentially re-implemented an existing function in part or full. In other words, is there an easier way of achieving this function without pulling the generator apart as much as I have in this implementation: http://lpaste.net/95317

[1] suchThat :: Gen a -> (a -> Bool) -> Gen a

http://hackage.haskell.org/package/QuickCheck-2.6/docs/src/Test-QuickCheck-G...

[2] suchThatMaybe :: Gen a -> (a -> Bool) -> Gen (Maybe a)

http://hackage.haskell.org/package/QuickCheck-2.6/docs/src/Test-QuickCheck-G...

-- Tony Morris http://tmorris.net/

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