make option suggestion

[Frederik Eaton]

The {-# ORIGIN ... #-} keyword sounds like a nice solution, but
wouldn't it require creating each generated file initially by hand, so
that the compilers know that it exists? I'd rather have a build system
where I can delete all of the generated files before distributing my
code, and still have compilation work. Maybe I'm not understanding.

Cheers,

Frederik

On Mon, Nov 06, 2006 at 09:37:18PM +0000, Neil Mitchell wrote:
> Hi
> 
> Just for completeness, I came up with a proposal that would solve all
> this, but in a very non-cabal style way.
> 
> Taking an example of happy, every generated file (File.hs) would have
> as its first line:
> 
> {-# ORIGIN happy sourcefile.y -options -to -happy #-}
> 
> Then you just modify all haskell generating tools to output this
> (easy) and suddenly the whole problem of preprocessors goes away.
> 
> I realise its not the "cabal" style way of doing it - since the
> information gets put in the generated files etc - but it is pretty
> simple.
> 
> You can also add to the file Happy.y:
> {-# GENERATE happy sourcefile.y -options -to -happy #-}
> 
> To complete the other side of the generation.
> 
> Thanks
> 
> Neil
> 
> On 11/6/06, Duncan Coutts <duncan.coutts at worc.ox.ac.uk> wrote:
> >I think this kind of build system feature ought to go into Cabal so it
> >can be used more widely and without people needing Makefiles.
> >
> >I admit that we're not there yet with how easy it is to generate source
> >files.
> >
> >Duncan
> >
> >On Mon, 2006-11-06 at 21:12 +0000, Frederik Eaton wrote:
> >> Hello,
> >>
> >> I have a proposal for ghc. I think that it should take a new option,
> >> say "--make-command". This will specify a command to be run whenever a
> >> source file is read in by ghc. The command will be passed an argument,
> >> which is the name of the source file. The idea is that the command can
> >> be used to create auto-generated "source" files when ghc needs them.
> >>
> >> The purpose of this would be the following. Suppose I have a source
> >> file, say Source.hs, which is generated from some template, say
> >> Source.hs.in. If I edit Source.hs.in, and compile my program with 'ghc
> >> --make', then the copy of Source.hs which ghc uses will be out of
> >> date. That's because ghc doesn't know about the fact that Source.hs is
> >> generated from Source.hs.in. If I use ghc, then I'll have to remember
> >> to manually generate a new version of Source.hs every time I modify
> >> Source.hs.in.
> >>
> >> But under the present proposal, I would simply write a Makefile with
> >> the rules for generating Source.hs, and then pass --make-command=make
> >> to ghc. For instance, my Makefile might say:
> >>
> >> Source.hs: Source.hs.in
> >>     $(TAC) < $< > $@
> >>
> >> Then every time I run ghc, and Source.hs is out of date, an up-to-date
> >> version of Source.hs will be generated automatically - because ghc
> >> will call 'make Source.hs' before reading it in.
> >>
> >> Does this sound like a good idea?
> >>
> >> Frederik
> >>
> >
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> >
> 

-- 
http://ofb.net/~frederik/