[Haskell-cafe] Re: nested maybes

[Max Vasin]

> Maybe has a Monad instance, so you can write this as follows (untested):

> exists str wmap = boolFromMaybe exists'
>   where exists' =
>             do x <- Map.lookup (sort str) wmap
>                find (== str) (snd x)
>         boolFromMaybe (Just _) = True
>         boolFromMaybe Nothing  = False

import isJust
boolFromMaybe = isJust

-- 
WBR,
Max Vasin.