[Haskell-cafe] Weird interaction between literate haskell, ghci and OverloadedStrings

[Erik de Castro Lopo]

Hi,

I'm working on a literate haskell document (actually TeX, but the
example below is just test) and I'm using ByteStrings in the code.
I know I can do:

    ghci -XOverloadedStrings file.lhs

or, after ghci is running I can do:

    Main> :set -XOverloadedStrings

but I'd like to embed a directive in the file so that when loaded
in GHCi, I will automatically get OverloadedStrings. This is mainly
so that it JustWorks(tm) when I pass the file on to someone else.

Is there a way to do this?

There is a short example file below. I'm using ghc-7.0.4 from Debian
testing.

Cheers,
Erik


----------8<----------8<----------8<----------8<----------
> {-# LANGUAGE OverloadedStrings #-}

This is just text that that ghc/ghci should ignore

> import Data.ByteString                     (ByteString)
> import qualified Data.ByteString.Char8     as BS

Simple function:

> newlineCount :: ByteString -> Int
> newlineCount bs = BS.foldl foldFun 0 bs
>   where foldFun s ch = if ch == '\n' then s + 1 else s

Once this file is loaded, I should be able to do this:

    newlineCount "abcd\ncdead\nasdasd\n"

----------8<----------8<----------8<----------8<----------



-- 
----------------------------------------------------------------------
Erik de Castro Lopo
http://www.mega-nerd.com/