Answer by Daniel Wagner for Use two monads without a transformer
The problem you're having is that the hand-unrolling of StateT s IO a is s -> IO (s, a), not IO (s -> (s, a))! Once you have this insight, it's pretty easy to see how to do it:go :: Int -> IO...
View ArticleAnswer by Matt for Use two monads without a transformer
Maybe this is what you are looking for?main = print =<< fmap (`evalState` 0) (go get) where go :: State Int Int -> IO (State Int Int) go st = do l <- getLine if null l then return (st...
View ArticleAnswer by dfeuer for Use two monads without a transformer
You'd just need to run the accumulated state computation on every line. This is O(n²) time, but since your first program is already using O(n) space, that's not too terrible. Of course, the StateT...
View ArticleUse two monads without a transformer
In order to understand how to use monad transformers, I wrote the following code without one. It reads standard input line by line and displays each line reversed until an empty line is encountered. It...
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