[Haskell-cafe] RE: [Haskell] ANNOUNCE: ghc-src version 0.2.0

[Simon Marlow]

On 30 August 2005 12:05, Arthur Baars wrote:

> Daan is right, I wrote a parser for GHC using Doaitse Swierstra's
> parsing combinator library
> (http://www.cs.uu.nl/groups/ST/Software/UU_Parsing/index.html).
> I needed a drop-in replacement for GHC's Happy parser, to make a
> prototype for syntax macros. Syntax Macros allow a programmer to
> extend a language with new syntax. Combinator based parsers parsers
> can be dynamically extended, making them suitable for implementing
> syntax macros.  Unfortunately, I never had time to really finish the
> syntax macro implementation.
> 
> But I did finish the combinator based parser for GHC. I tested it by
> having GHC( with combinator parser) compile itself and all the
> libraries. This took about 10% longer than with the original GHC, so
> in practice its speed is acceptable.

With all due respect, a 10% increase in compile time isn't acceptable at
all!

And when you consider that parsing is less than 10% of compile time
overall (probably much less), a 10% increase represents at least a
factor of 2 in the parser.

I'm not criticising the work at all - far from it, just the notion that
we would consider adding 10% to GHC's compile times "acceptable".  I've
recently  been struggling to shave a few percent off GHC's compile
times, BTW :-)

Cheers,
	Simon