From: "Hal E. Fulton" <hal9000@...>
Date: 2001-05-09T11:33:50+09:00
Subject: [ruby-talk:14891] Re: ANTLR rules for Ruby

----- Original Message -----
From: Juancarlo Anez <juanca-l@suigeneris.org>
To: ruby-talk ML <ruby-talk@ruby-lang.org>
Sent: Tuesday, May 08, 2001 5:54 PM
Subject: [ruby-talk:14885] Re: ANTLR rules for Ruby


> I worked plenty with YACC while I was a student, and learned how difficult
> it is to debug, maintain, enhance, and optimize table-driven parsers.
> Top-down, procedural parsers are completely the opposite. A top down
parser
> pays out in the short term even if it has to be written by hand.
>

[some snips]

> Anyway, ANTLR or not, I can't recommend a top-down parser enough.

I've heard other people say the same thing -- basically that yacc is easy
but
the code can't compare with what you write by hand.

I'm the opposite of most people, it seems -- I've never used yacc or the
moral
equivalent, but I have written a few recursive-descent parsers.

Coming from my early [cough] Pascal background, I found I always "thought"
in terms of Pascal-like syntax diagrams, and found that they translated very
nicely into code.

Of course, my Pangloss language which I implemented for CS 450 (Theory of
Programming Languages) all those years ago was an order of magnitude
simpler than Ruby in terms of syntax.

> How about a top-down parser written in Ruby? It would be a short, easy,
and
> fun experiment.

I myself would never describe it as short and easy. But I'll take your word
for it.

[snip again]

Even if this isn't an "official" project, there's nothing to stop you from
doing it
yourself... witness Meta-Ruby and others.

And if it turns out well, you'll be a minor hero, or at least have earned a
little
respect from the community. So go for it!

Hal