On Tue, Oct 28, 2008 at 9:44 PM, Niklas Broberg <[EMAIL PROTECTED]> wrote: > On Tue, Oct 28, 2008 at 7:56 AM, Reiner Pope <[EMAIL PROTECTED]> wrote: >> 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. > > Care to tell me what the problem is? I have no problem installing it > with GHC 6.10, in fact the 0.3.9 version on hackage was uploaded > solely to have it compile with both old and new GHC.
Running "cabal install haskell-src-exts" gave > Resolving dependencies... > 'haskell-src-exts-0.3.9' is cached. > Configuring haskell-src-exts-0.3.9... > Preprocessing library haskell-src-exts-0.3.9... > Building haskell-src-exts-0.3.9... > > Language/Haskell/Exts/Syntax.hs:102:7: > Could not find module `Data.Data': > it is a member of package base, which is hidden > cabal: Error: some packages failed to install: > haskell-src-exts-0.3.9 failed during the building phase. The exception was: > exit: ExitFailure 1 I am using GHC 6.10.0.20081007. Modifying the dependencies in the haskell-src-exts.cabal file to > if flag(splitBase) > Build-Depends: base == 4.*, array >= 0.1, pretty >= 1.0 allows it to compile. > >> Unfortunately, I've uncovered a problem in the parser. For instance, >> with your module, [$hs|1+1*2|] evaluates to 4 rather than 3. This >> seems to be a general problem with infix operators, which I believe >> arises since haskell-src-exts isn't given the fixity declarations for >> + and *, so it doesn't know to bind (*) tighter than (+). I don't see >> how this problem can even be resolved without modifying Template >> Haskell: given that the operators reside in user code, there is no way >> to find their fixity. > > Yes, you're right, haskell-src(-exts) does not handle fixity of > operators for you. You need to collect the fixities yourself and make > a second pass over expressions to get them right. This is definitely > functionality I would like to see available in haskell-src-exts > (though not on by default), so if anyone were to implement it I would > gladly accept patches. > The problem in the case of quasi-quoting is worse than this, though. I create my quasiquoter library, and it will parse Haskell syntax including infix operators. A user may then write, eg >(*+*) = undefined >infixr *+* > >foo = [$hs|5*+*4+3|] The hs quasiquoter has no way of knowing *+*'s fixity, and template haskell provides no way to find out, as far as I know. The quasiquoter's parser only has access to the string, "5*+*4+3". Cheers, Reiner _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
