ghc command line evaluation

[Pedro Miguel Duarte]

Thanks a lot for the sugestions!
I am going to try them...

pedro


On 4/5/06, Björn Bringert <bringert at cs.chalmers.se> wrote:
>
> Benjamin Franksen wrote:
> > On Wednesday 05 April 2006 20:32, Pedro Miguel Duarte wrote:
> >
> >>I am writing a Java program with a call to a  Haskell module  M.hs,
> >>in order to evaluate some expression   expr.
> >>
> >>A very simple idea, which I got somewhere in the net,  is to create a
> >>Process object p  which executes a GHC command-line instruction:
> >>
> >>Process p = Runtime.getRuntime();
> >>p.exec( " ghc M.hs  -e \"expr\" " );
> >>
> >>
> >>This would be very simple, if it worked...
> >>
> >>
> >>My problem is that  expressions i want to evaluate involve
> >>strings, and GHC command-line  'ghc' misinterprets some special
> >>symbols when it  parses double quoted strings.
> >>
> >>For instance,
> >>     ghc -e  " reverse \"2<3\" "     gives an error!
> >
> >
> > Hmm. On my Linux machine (running zsh):
> >
> > ben at sarun: .../play/ghc-e > ghc -e  " reverse \"2<3\" "
> > "3<2"
> >
> > But now I see that you run 'p.exec' in Java which probably translates
> > (more or less) to a 'exec' system call. 'exec' is not a shell, it
> > cannot translate complex quotings and unquotings. I would try
> >
> > p.exec( "/bin/sh ghc M.hs  -e \"expr\" " );
> >
> > or something similar.
>
> Another way could be to use one of the other exec() methods (which BTW
> are available from the Runtime class, not the Process class). For
> example, using the "exec(String[] cmdarray)" version, you could write
> something like (not tested):
>
> Runtime r = Runtime.getRuntime();
> Process p = r.exec(new String[]{"ghc", "-e", expr});
>
> /Björn
>
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