Ah, quite simple. Thanks! On Tue, Jun 19, 2018 at 9:39 PM, Matt wrote:

showText text = do a <- showA return ("[" `append` text `append` a `append` "]")

Matt Parsons

On Tue, Jun 19, 2018 at 10:35 PM, Hilco Wijbenga wrote:

...

Hi all,

I think I'm pretty close but not quite there yet. Let's say I have the following:

{-# LANGUAGE OverloadedStrings #-}

module Main where

import Prelude (IO) import Data.Text (Text, append) import Data.Text.IO (putStrLn)

main :: IO () main = putStrLn (showText "Hello World!" config) where config :: Config config = Config (A "Boo")

data A = A Text

data Config = Config { a :: A }

showText :: Text -> Config -> Text showText text config = "[" `append` text `append` (showA config) `append` "]"

showA :: Config -> Text showA config = "'" `append` text `append` "'" where A text = a config

Now I want to use Reader. This is as close as I can get:

{-# LANGUAGE OverloadedStrings #-}

module Main where

import Prelude (IO, return, ($)) import Data.Text (Text, append) import Data.Text.IO (putStrLn) import Control.Monad.Reader (Reader, asks, runReader)

main :: IO () main = putStrLn (runReader (showText "Hello World!") config) where config :: Config config = Config (A "Boo")

data A = A Text

data Config = Config { a :: A }

showText :: Text -> Reader Config Text showText text = return $ "[" `append` text `append` showA `append` "]"

showA :: Reader Config Text showA = do A text <- asks a return $ "'" `append` text `append` "'"

This is almost correct, except for the showA invocation in showText. It wants a Text but it's getting a Reader Config Text. What is the magic to make this work?

Cheers, Hilco _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.