From: Lennon Day-Reynolds <rcoder@...>
Date: 2004-08-03T02:45:10+09:00
Subject: Re: Macros in Ruby

On Tue, 3 Aug 2004 02:29:34 +0900, James Britt
<jamesunderbarb@neurogami.com> wrote:
> Is there something different about Ruby such that what (supposedly)
> works to such acclaim in Lisp would be inappropriate in Ruby?

A: S-expressions, or the lack thereof in Ruby. Lisp code can always be
manipulated as a simple tree of cons cells; Ruby code, even if a
high-level programmatic interface existed to the AST, has a much
richer syntax, and therefore more complex structure.

Also, as has been mentioned, Ruby largely replaces macros with blocks
-- they allow delayed evaluation, specialized iteration and
pre/post-condition checks, etc. Many of the common macros you'll see
in Lisp are things like this:

(with-open-file "foo.dat" my-file (case (read-char my-file) ...))

[my apologies for the weird function names; it's been a couple of
years since I was actively developing any Lisp code]

Obviously, that example is quite handily supported by the more
Ruby-esque example below:

open("foo.dat") {|my_file| case my_file.getc ...}

Personally, I think macros could be an interesting tool for very
special cases, but they're not an essential feature for 90% of
developers. Now, exposing the AST with a high-level API could have
other benefits: code analysis and optimization, JIT compilers,
documentation generators, etc.

Lennon