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
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.
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
I need to write a state monad that can also support error handling. I was thinking of using the Either monad for this purpose because it can also provide details about what caused the error. I found a
In what situations should liftIO be used? When I\'m usi开发者_Python百科ng ErrorT String IO, the lift function works to lift IO actions into ErrorT, so liftIO seems superfluous.lift always lifts from
I am trying to build a MaybeT-Transformer Monad, based on the example in the Real World Haskell, Chapter Monad Transformers:
In my area of business - back office IT for a financial institution - it is very common for a software component to carry a global configuration around, to log its progress, to have some kind of error
I\'m trying to create a monad transformer for a future project, but unfortunately, my implementation of the Monad typeclasse\'s (>>=) function doesn\'t work.
I am attempting to create a stack of monad transformers and am having trouble getting the correct type signatures for my functions. (I\'m still pretty new to Haskell)
I have function f with signature f :: [a] -> StateT Int Reader b [c], and f\' with signature f\' :: a -> StateT Int Reader b [c]
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