cabal: question on compiling build prerequisites

[Dag Odenhall]

How about -pgmF runghc -optF PreProc?


On Mon, Dec 9, 2013 at 12:48 AM, Peter Selinger <selinger at mathstat.dal.ca>wrote:

> Thanks for the suggestion! However, it is not portable: it doesn't
> work on Windows.
>
> Similarly, giving "runhaskell ./PreProc.hs" as the preprocessor
> command to GHC doesn't work either, because GHC will try to run a
> program with that exact name (including the space), rather than
> interpreting it as a command with an argument.
>
> In addition, even on Posix systems, where the above method does work,
> it is nevertheless extremely slow: runhaskell will have to interpret
> or compile ./PreProc.hs separately for each source file, of which
> there could be many.
>
> Another solution I thought of is to include
>
>  import Preproc
>
> at the beginning of Setup.hs. This way compiling Setup.hs would have
> the side effect of compiling Preproc.hs. It would not work with the
> "runhaskell Setup.hs" method, though.
>
> -- Peter
>
> Erik Hesselink wrote:
> >
> > On Sun, Dec 8, 2013 at 7:50 PM, Peter Selinger <selinger at mathstat.dal.ca>
> wrote:
> > > thanks for your reply! So say my package directory contains two files:
> > >
> > >  Test.hs
> > >  PreProc.hs
> > >
> > > What you are suggesting is:
> > >
> > >  ghc Test.hs -F -pgmF ./PreProc
> > >
> > > However, this gives the error message:
> > >
> > >  ghc: could not execute: ./PreProc
> > >
> > > And indeed, while GHC is smart enough to automatically run a
> > > preprocessor, it is not smart enough to automatically *compile* the
> > > preprocessor. So it needs to be compiled beforehand, which would be
> > > Cabal's job.
> >
> > Not per se. You could try making it executable, and prepending a line
> like:
> >
> > #!/usr/bin/env runhaskell
> >
> > That way you can run your preprocessor like a script, without compiling
> it.
> >
> > Erik
> >
>
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