communication with ghci from haskell

[Simon Peyton-Jones]

Is there some reason you need to run GHCi as a separate process?  By doing so, you constrain yourself to communicating with it using inter-process communication (like pipes).  Maybe signals too.. but that becomes jolly tricky when you want to port across platforms.

The obvious alternative is to use GHC as a library.  That is the way GHCi currently works: a small interactive loop sitting on top of a big library.  Very partial info here
        http://haskell.org/haskellwiki/GHC/As_a_library

I think that'd be a lot easier.  If you want to maintain responsiveness of the GUI, when kicking off an evaluation that uses lots of time, you can use Haskell threads.

Simon

| -----Original Message-----
| From: cvs-all-bounces at haskell.org [mailto:cvs-all-bounces at haskell.org] On Behalf Of
| Hackler at Mathematik.Uni-Marburg.de
| Sent: 20 November 2006 15:01
| To: cvs-ghc at haskell.org
| Subject: communication with ghci from haskell
|
| Dear experts,
|
| we are currently developing a GUI for GHCi in Haskell using gtk2hs. We
| have encountered a problem concerning the communication with GHCi. In the
| current version we run GHCi in the background using the
| "runInteractiveProcess" function from the module System.Process. The main
| difficulty is that we don't see any possibility to determine when GHCi has
| finished its computation and is awaiting user input, that is to say, we
| don't know if there are any appropriate signals from GHCi that we could
| somehow handle in Haskell. Our program already works as long as we just
| execute some "standard" evaluations, but as soon as we do something
| "extravagant" like e.g. nonterminating evaluations (say cycle [1,2,3]), or
| certain IO-processes we can neither display the output up to the current
| point of evaluation nor interrupt the calculation. We hope to have
| described our problem precisely enough and would greatly appreciate any
| helpful hint. Thanks a lot!
|
| Greets
|
| Matthias Stemmler and Bastian Hackler
|
| University of Marburg, Germany
| _______________________________________________
| Cvs-ghc mailing list
| Cvs-ghc at haskell.org
| http://www.haskell.org/mailman/listinfo/cvs-ghc