Re: Advance notice that I'd like to make Cabal depend on parsec

On Fri, 2013-03-15 at 05:19 +0100, Bardur Arantsson wrote:

On 03/14/2013 11:01 PM, Duncan Coutts wrote:

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On Thu, 2013-03-14 at 11:15 -0700, Jason Dagit wrote:

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On Thu, Mar 14, 2013 at 11:01 AM, Bardur Arantsson wrote:

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On 03/14/2013 03:53 PM, Duncan Coutts wrote:

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Hi folks,

Why did I choose parsec? Practicality dictates that I can only use things in the core libraries, and the nearest thing we have to that is the parser lib that is in the HP. I tried to use happy but I could not construct a grammar/lexer combo to handle the layout (also, happy is not exactly known for its great error messages).

Just thinking out loud here, but what about ditching the current format for something that's simpler to parse/generate? Like, say, JSON?

Of course .cabal files are mainly written by humans, not machines, so we should optimise for them.

I though we were mostly talking about InstalledPackageInfo. That could be in $EASILY_PARSEABLE_FORMAT without really breaking anything, right?

In principle it could be any format. But it is a format specified in the Cabal spec, and shared between all the Haskell implementations. Unless there's a compelling reason to change all that, I'd rather not.

Another option if GHC really also needs to parse .cabal files:

That's ok, it doesn't. GHC use Cabal when building ghc, but at runtime it's just using the InstalledPackageInfo type, parser (and perhaps some index utils). -- Duncan Coutts, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/