Re: [Haskell-cafe] generating parens for pretty-printing code in haskell-src-exts
Neil Mitchell's HLint (http://community.haskell.org/~ndm/hlint/) warns about "extra parens" in Haskell code. So, it must have code for detecting those. I wonder if you can just insert parens liberally in a first run, and then use his algorithm to remove those that are unnecessary. The two passes can probably be fused, if you're willing to use haskell-stc-exts and do a bit of bookkeeping.. -Levent. On Sat, Jan 21, 2012 at 10:39 AM, Niklas Broberg wrote: > Hi Conal, > > On Sun, Jan 15, 2012 at 6:45 AM, Conal Elliott wrote: >> >> I'm using haskell-src-exts together with SYB for a code-rewriting project, >> and I'm having difficulty with parenthesization. I naïvely expected that >> parentheses would be absent from the abstract syntax, being removed during >> parsing and inserted during pretty-printing. It's easy for me to remove them >> myself, but harder to add them (minimally) after transformation. Rather than >> re-inventing the wheel, I thought I'd ask for help. > > > It's not at all straight-forward to properly insert minimal parentheses > during pretty-printing, since "minimal" is a semantic notion. For that to > work, we would need the pretty-printer to take a set of known fixities as an > argument, just like the parser currently does. I'm not opposed to the idea > in principle, but it's not how it currently works. > >> >> Has anyone written automatic minimal parens insertion for >> haskell-src-exts? > > > ... or we could do it this way, in a two-stage modular process which gives > even more flexibility. I'm not aware of any such functionality, currently, > but if it exists (or happens to come into existence) then I would be > interested in including it in haskell-src-exts. > > Best regards, > > /Niklas > > ___ > 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
Re: [Haskell-cafe] generating parens for pretty-printing code in haskell-src-exts
Hi Conal, On Sun, Jan 15, 2012 at 6:45 AM, Conal Elliott wrote: > I'm using haskell-src-exts together with SYB for a code-rewriting project, > and I'm having difficulty with parenthesization. I naïvely expected that > parentheses would be absent from the abstract syntax, being removed during > parsing and inserted during pretty-printing. It's easy for me to remove > them myself, but harder to add them (minimally) after transformation. > Rather than re-inventing the wheel, I thought I'd ask for help. > It's not at all straight-forward to properly insert minimal parentheses during pretty-printing, since "minimal" is a semantic notion. For that to work, we would need the pretty-printer to take a set of known fixities as an argument, just like the parser currently does. I'm not opposed to the idea in principle, but it's not how it currently works. > Has anyone written automatic minimal parens insertion for haskell-src-exts? > ... or we could do it this way, in a two-stage modular process which gives even more flexibility. I'm not aware of any such functionality, currently, but if it exists (or happens to come into existence) then I would be interested in including it in haskell-src-exts. Best regards, /Niklas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] generating parens for pretty-printing code in haskell-src-exts
Hi Conal I don't know if any Haskell src-exts code exists. Norman Ramsey has published an algorithm for it, plus ML code: http://www.cs.tufts.edu/~nr/pubs/unparse-abstract.html I've transcribed the code to Haskell a couple of times for small expression languages. As far as I remember you need to know what constructors you are working with so it can't be put in a "generic" pretty print library, but the constructor specific code is "stereotypical" so it should be easy (if boring) to write for Haskell src-exts. Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] generating parens for pretty-printing code in haskell-src-exts
I'm using haskell-src-exts together with SYB for a code-rewriting project, and I'm having difficulty with parenthesization. I naïvely expected that parentheses would be absent from the abstract syntax, being removed during parsing and inserted during pretty-printing. It's easy for me to remove them myself, but harder to add them (minimally) after transformation. Rather than re-inventing the wheel, I thought I'd ask for help. Has anyone written automatic minimal parens insertion for haskell-src-exts? -- Conal ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
