For doinjg this sort of thing I have used asdl before
which I find really useful.
> -----Original Message-----
> From: Manuel M. T. Chakravarty [mailto:[EMAIL PROTECTED]]
> Sent: 23 August 2000 14:09
> To: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]
> Subject: Re: code generation for other languages
>
>
> Jeffrey Straszhiem <[EMAIL PROTECTED]> wrote,
>
> > On Wed, Aug 23, 2000 at 12:26:38PM +1000, Timothy Docker wrote:
> > >
> > > I'm writing a haskell program that generates C++ code based upon
> > > some haskell data structures. At the moment, the code is somewhat
> > > ugly with lots of stuff like
> > >
> > > mutatorDef structName (name,vtype) =
> > > "inline void\n" ++
> > > structName ++ "::" ++ (mutatorName name) ++
> > > "( " ++ (cppParamType vtype) ++ " v ) {\n" ++
> > > " " ++ (storageName name) ++ " = v;\n" ++
> > > "}\n\n"
> > >
> > > All those ++ operators working on raw strings bug me, and manually
> > > getting the indentation correct is a pain. Is there a more
> > > functional approach to generating source code? I thought
> this could
> > > be a common enough task that there could be a library,
> but a perusal
> > > of haskell.org didn't seem to show anything relevant.
> >
> > To make matters worse, you're likely getting lousy
> efficiency with all
> > of the ++ operators. Look through the code for showS in the Prelude
> > for better ways to hook strings together. Paul Hudak talks
> about the
> > efficient use of the show functions at:
> >
> > http://www.haskell.org/tutorial/stdclasses.html
> >
> > Now, with regard to the code being ugly, my suggestion would be to
> > check out some of the pretty printer libraries out there,
> and to look
> > through them. They basically solve a similar problem, except they
> > first parse a normal program into a tree, then flatten the tree in a
> > standard way. In your case you'll likely build the tree directly,
> > then call the final stages of the pretty printer. There is no
> > shortage of pretty printer libraries for Haskell, or for FP in
> > general.
>
> The canonical approach is to define an internal data
> structure that represents C++ code, then let your mutator
> functions generate values of that data type (instead of
> strings), and finally pretty print values of this C++ data
> structure. That's cleaner and more flexible than the ++
> cascades (or the show equivalent).
>
> Depending on how restricted and/or idiomatic the generate
> C++ code is, it makes sense to not have a data structure
> that can represent arbitrary C++ programs, but only a subset
> that is relevant for the code generation task at hand. So,
> you might want functions like
>
> mutatorDef :: ... -> AbstractCPlusPlus
>
> prettyPrintACPP :: AbstractCPlusPlus -> String
>
> Cheers,
> Manuel
>
