I've tried it out and it looks good so far. I had to fiddle with haskell-src-ext's .cabal file to get it to install with GHC 6.10, which is surprising since it isn't listed as a broken package... ah well.
I'm able to write code like this now: > foo x = [$vec|sin x, myFunc x, 4*5|] Since Haskell expressions are not the entire grammar, I'm actually making a very simple parsec lexer/bracket-counter whose sole purpose is to find where the haskell expression stops (at a comma). This lexer then just passes the string verbatim onto parseExp. Unfortunately, I've uncovered a problem in the parser. For instance, with your module, [$hs|1+1*2|] evaluates to 4 rather than 3. This seems to be a general problem with infix operators, which I believe arises since haskell-src-exts isn't given the fixity declarations for + and *, so it doesn't know to bind (*) tighter than (+). I don't see how this problem can even be resolved without modifying Template Haskell: given that the operators reside in user code, there is no way to find their fixity. Cheers, Reiner On Mon, Oct 27, 2008 at 12:22 AM, Matt Morrow <[EMAIL PROTECTED]> wrote: > I've just uploaded an alpha version of the translation to hackage: > > http://hackage.haskell.org/cgi-bin/hackage-scripts/package/haskell-src-meta-0.0.1 > > (I starting thinking after I uploaded that maybe haskell-src-th is a > better name..) > > Here's one strategy for a haskell QQ: > > ------------------------------------------------------------ > module HsQQ where > > import Language.Haskell.Meta > import Language.Haskell.TH.Lib > import Language.Haskell.TH.Quote > import Language.Haskell.TH.Syntax > > -- | > -- > ghci> [$hs|\x -> (x,x)|] 42 > -- > (42,42) > -- > ghci> (\[$hs|a@(x,_)|] -> (a,x)) (42,88) > -- > ((42,88),42) > hs :: QuasiQuoter > hs = QuasiQuoter > (either fail transformE . parseExp) > (either fail transformP . parsePat) > > transformE :: Exp -> ExpQ > transformE = return > > transformP :: Pat -> PatQ > transformP = return > ------------------------------------------------------------ > > I'll post updates as I add to the pkg over the next few days. > > Cheers, > Matt > > > > On 10/21/08, Reiner Pope <[EMAIL PROTECTED]> wrote: >> It sounds like you're doing exactly what I'm looking for. I look forward to >> more. >> >> Reiner >> >> On Tue, Oct 21, 2008 at 4:28 PM, Matt Morrow <[EMAIL PROTECTED]> wrote: >> >>> > Is there a simple way to do this, i.e. using existing libraries? >>> >>> Yes indeed. I'll be traveling over the next two days, and am shooting >>> for a fully functional hackage release by mid next week. >>> >>> > What I need is a Haskell expression parser which outputs values of type >>> > Language.Haskell.TH.Syntax.QExp, but I can't see one available in the TH >>> > libraries, or in the haskell-src(-exts) libraries. >>> >>> My strategy is to use the existing haskell-src-exts parser, then >>> translate that AST to the TH AST. >>> >>> Once I've got settled in one place, I'll follow up with a brain dump :) >>> >>> > Cheers, >>> > Reiner >>> >>> Matt >>> _______________________________________________ >>> Haskell-Cafe mailing list >>> Haskell-Cafe@haskell.org >>> http://www.haskell.org/mailman/listinfo/haskell-cafe >>> >> > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
