I found some sample code, and changed it a little counter = unsafePerform $ newIORef 0 newNode _ = unsafePer开发者_如何转开发formIO $
my goal is to write Haskell function which reads N lines from input and joins them in one string. Below is the first attempt:
This section http://book.realworldhaskell.org/read/monad-transformers.html#id659032 from the book Real World Haskell suggests that when writing a new Monad Transformer, we have to derive instances for
What I\'m trying to do is (in a module I\'m writing) export a function that works on a particular type in a state monad (in the example below, that type would be Foo). However I would like the user to
Can anybody give an example of using scalaz Monad for a simple 开发者_开发技巧but non-trivial and practically useful task ?scalaz.Monad, and the family of related type classes, abstract some common fu
how is meant to work Option monad? I\'m browsing the scala api and there is an example (I mean the second one),
I do not understand what the problem is. \'a\' is not a bool and should not be a bool. So why is bool expected?
Let\'s say we want to use ReaderT开发者_开发问答 [(a,b)] over the Maybe monad, and then we want to do a lookup in the list.
guard :: (MonadPlus m) => Bool开发者_开发知识库 -> m () guard True= return () guard False = mzero
Lets say I have a function f :: State [Int] Int and a function: g :: StateT [Int] IO Int I want to use f in g and pass the state between them. Is there a library function for
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