May 18, 2011
Goldie Parsing System v0.5 is now out. This version focuses mainly on speed improvements.

== Links: ==

Homepage and Documentation:
    http://www.semitwist.com/goldie/

Prepackaged Downloads:
    http://www.dsource.org/projects/goldie/browser/downloads

== New in v0.5: ==

    - Improved lexing/parsing speed by about 5x-6x.

    - Small additional speedup lexing languages with large character sets
(such as Unicode).

    - GRMC: Grammar Compiler: Supports {All Valid} character set.

    - GRMC: Grammar Compiler: Complex grammars are compiled to CGT up to
about 4x-8x faster.

    - GRMC: Grammar Compiler: Verbose (-v) flag shows each step and amount
of time taken.

    - Parse Anything: No more unhandled exception when parsing a source with
an error.

    - Fixed to work with DMD 2.053 (still works with 2.052, too).

There are still more optimizations than can be done, but I felt this was enough to warrant a new release.


May 18, 2011
On 18.05.2011 05:47, Nick Sabalausky wrote:
> Goldie Parsing System v0.5 is now out. This version focuses mainly on speed
> improvements.
>
> == Links: ==
>
> Homepage and Documentation:
>      http://www.semitwist.com/goldie/
>
> Prepackaged Downloads:
>      http://www.dsource.org/projects/goldie/browser/downloads
>
> == New in v0.5: ==
>
>      - Improved lexing/parsing speed by about 5x-6x.
>
>      - Small additional speedup lexing languages with large character sets
> (such as Unicode).
>
>      - GRMC: Grammar Compiler: Supports {All Valid} character set.
>
>      - GRMC: Grammar Compiler: Complex grammars are compiled to CGT up to
> about 4x-8x faster.
>
>      - GRMC: Grammar Compiler: Verbose (-v) flag shows each step and amount
> of time taken.
>
>      - Parse Anything: No more unhandled exception when parsing a source with
> an error.
>
>      - Fixed to work with DMD 2.053 (still works with 2.052, too).
>
> There are still more optimizations than can be done, but I felt this was
> enough to warrant a new release.
>
>

Great work.

Is it possible to generate a parser for D with this ?

Regards,
Stephan
May 18, 2011
"Stephan" <spam@extrawurst.org> wrote in message news:ir05te$tbd$1@digitalmars.com...
> On 18.05.2011 05:47, Nick Sabalausky wrote:
>> Goldie Parsing System v0.5 is now out. This version focuses mainly on
>> speed
>> improvements.
>>
>
> Great work.
>

Thanks :)

> Is it possible to generate a parser for D with this ?
>

It should be possible to write a grammar that handles most of D. But there would be some awkwardness and corner cases that, to really be handled right, would need some enhancements I haven't put in yet.

For example:

- Nested comments aren't yet officially supported. GOLD (which Goldie is based on) will support them in the currently-in-beta v4.2 ( http://www.devincook.com/goldparser/v4.2.htm ). I intend to make Goldie fully compatible with all the new GOLD v4.2 features, but just haven't gotten to them yet. In the meantime, what you can do is lex the D source first, then go through the resulting token array removing everything from a "/+" token to its matching "+/" token (there will be a bunch of junk in between, including some error tokens, you can just rip it all out), and then send that through the parser.

- Another comment-related thing that'll be fixed with the v4.2 enhancements: Currently, GOLD and Goldie handle (non-nested) block comments by actually lexing what's inside the comment (and ignoring any errors). Normally this works out fine, but it does lead to some occasional edge-cases where the "*/" isn't handled right.

- D relies on certain disambiguation rules. For instance: "a*b" could be either a multiplication expression or a pointer declaration. D handles this by saying "if something can be either an expression or a declaration, then always interpret it as (umm...actually I forget which one it always chooses, but it's always that same one)". Goldie (and GOLD) currently doesn't have any conflict resolution. If you try to create a grammar that has such an ambiguity, you'll just get a "reduce-reduce conflict" error, or "shift-reduce" problems. The way to work around this is to design the grammar to completely conflate the two notions, so instead of having <Expression> and <Declaration>, you'd just have something like <ExprOrDecl>. Unfortunately, this isn't always easy, it does tend to obfuscate the grammar, it makes the nonterminals less meaningful, and it'll create much more work for your semantics pass. I do intend to solve this, but it'll probably be a very non-trival matter. More discussion (possibly a bit technical) on this issue is here: http://groups.google.com/group/gold-parsing-system/browse_thread/thread/5959e0cfef76ce68

FWIW, Goldie does include a lex-only grammar for D2, which could be used as a starting point (although it's possible I might have gotten some edge cases wrong regarding the decimal literals. Also, this grammar is currently ASCII-only, but that can easily be changed):

http://www.dsource.org/projects/goldie/browser/tags/v0.5/lang/dlex.grm




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