Thanks, Daniel. I'm still stumped. When I say #include "B.hs" in a .hs file, all works fine, but when in a .lhs file I get "error: B.hs: No such file or directory". The file B.hs is in the same directory as the including file, which is the current directory for ghci. Same situation with ghc. If I change "B.hs" to "./B.hs", I get the same behavior. Only if I use a fully qualified path name for B.hs does it get found from the .lhs file. I'm using GHC 6.12.3 on Mac OS 10.6.6. Any ideas? (Anyone, not just Daniel.) Thanks, - Conal On Thu, Feb 3, 2011 at 2:51 AM, Daniel Fischer < daniel.is.fischer@googlemail.com> wrote:

On Thursday 03 February 2011 10:33:23, Conal Elliott wrote:

...

Does anyone have a working example of #include'ing Haskell code into a bird-tracks-style .lhs file with GHC? Every way I try leads to parsing errors. Is there documentation about how it's supposed to work?

Help much appreciated. - Conal

Stupid example:

-- Main:

...

{-# LANGUAGE CPP #-} module Main (main) where

#include "MachDeps.h"

...

main :: IO () main = do

#if WORD_SIZE_IN_BITS == 32

...

putStrLn "32 bits"

#include "Stuff32"

# else

...

putStrLn "64 bits"

#include "Stuff64" #endif

-- Stuff32:

putStrLn "Included from Stuff32"

-- Stuff64:

putStrLn "Included from Stuff64"

It's a bit tricky. Since the C preprocessor is run after the unlit, the included code should not have bird-tracks, also you have to get the indentation right. There's probably a way to run cpp before unlit, which would allow you to have bird-tracks in the #include'd code.

Much easier with LaTeX-style literate code.

Cheers, Daniel

On 4 February 2011 05:03, Michael Snoyman wrote:

My guess (a complete guess) is that the deliterate step is creating a temporary .hs file elsewhere on your filesystem, which is why the CPP step can't find B.hs without a fully-qualified path.

That is what is happening (you can confirm with "ghc -v"). Interestingly, you can work around by compiling with -I. on the command line: {{{ mbolingbroke@equinox ~/Junk/lhscpp $ cat Test.lhs Included.h

{-# LANGUAGE CPP #-} module Main (main) where

#include "MachDeps.h" #include "Included.h"

main :: IO () main = print MY_CONSTANT #define MY_CONSTANT 2 mbolingbroke@equinox ~/Junk/lhscpp $ ./Test 2 }}}

Perhaps worth filing a bug report? Cheers Max