[Haskell-cafe] Template Haskell antiquotation in user-defined quasiquoters

[Mike Ledger]

(oops, sorry, didn't do reply to all)

I use haskell-src-meta in QuasiText (on hackage) also. It would certainly
be nice to have "native" anti-quotations, but for now haskell-src-meta does
a very good job.

Mike
On Sat, May 26, 2012 at 8:31 AM, Geoffrey Mainland <mainland at apeiron.net>wrote:

> On 05/25/2012 21:46, Antoine Latter wrote:
> > On Fri, May 25, 2012 at 2:51 PM, Sam Lindley <Sam.Lindley at ed.ac.uk>
> wrote:
> >> Template Haskell supports antiquotation for built-in quasiquotes, e.g.:
> >>
> >>  [| \x -> x + $([|3 * 4|]) |]
> >>
> >> However, as far as I can tell, there is no way of supporting
> antiquotation
> >> in user-defined quasiquoters, because the only way to specify a new
> >> quasiquoter is through a quoteExp function of type String -> Q Exp. Of
> >> course, it is perfectly possible to write a parser for some fragment of
> >> Haskell inside your quoteExp function, but that seems crazy given that
> >> Template Haskell or rather GHC already implements a parser for the whole
> >> language.
> >>
> >> I know about Language.Haskell.Exts.Parser in haskell-src-exts, which
> >> provides parseExp :: String -> ParseResult Exp, but that Exp is a
> different
> >> type to the one provided by Template
> >> Haskell.<
> http://hackage.haskell.org/packages/archive/haskell-src-exts/1.9.0/doc/html/Language-Haskell-Exts-Syntax.html#t:Exp
> >
> >> I'm also aware of Dominic Orchard's syntax-trees package, which supports
> >> converting between the two representations using a cunning hack that
> >> pretty-prints the haskell-src-exts representation to a string and uses
> >> Template Haskell to parse it back.
> >>
> >> Is there a saner way of simulating antiquotation in user-defined
> >> quasiquoters?
> >>
> >
> > Have you looked at:
> >
> > http://hackage.haskell.org/package/haskell-src-exts-qq
> > http://hackage.haskell.org/package/haskell-src-meta
> >
> > The might help you pull something together.
> >
> >
> > Antoine
> >
> >> Sam
>
> I use haskell-src-meta in language-c-quote (also on hackage) to support
> antiquotation and heartily endorse it. I have not used haskell-src-exts-qq.
>
> Geoff
>
>
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