From: Austin Ziegler <halostatue@...>
Date: 2008-11-10T23:50:05+09:00
Subject: [ruby-core:19779] Re: Proposal: Method#get_args

On Mon, Nov 10, 2008 at 9:24 AM, Dave Thomas <dave@pragprog.com> wrote:
> On Nov 10, 2008, at 7:54 AM, Brian Candler wrote:
>>> However, a class feels too heavyweight for the metaprogramming case,
>>> while the anonymous tuple feels a little too lightweight and devoid
>>> of context, at least to me.
>> A Struct perhaps? You can always use to_a to get a tuple back.
> Or an array of strings?
>
>  def fred(a, b=2, *c, &block)
>  end
>
>  method(:fred).arguments => ["a", "b=2", "*c", "&block" ]

That feels a little better from my ability to understand it, but then
programs which want to do metaprogramming have to do a lot of extra work
(split on /=/; know that "*" means greedy, etc.). I was sort of thinking
an array of Hashes, but that's not necessarily any lighter weight than a
Struct or a dedicated class.

  method(:fred).arguments =>
    [ { :name => :a },
      { :name => :b, :default => 2 },
      { :name => :c, :greedy => true },
      { :name => block, :block => true } ]

Playing with some other constructs:

  def wilma(a, *, c); end
  method(:wilma).arguments =>
    [ { :name => :a },
      { :name => nil, :greedy => true },
      { :name => :c } ]

  def barney(a, b, c = b); end
  method(:barney).arguments =>
    [ { :name => :a },
      { :name => :b },
      { :name => :c, :default => :b } ]

I'm not really happy with the last -- because it conflicts with:

  def betty(a, b, c = :b); end
  method(:betty).arguments =>
    [ { :name => :a },
      { :name => :b },
      { :name => :c, :default => :b } ]

Or would that be:

  method(:betty).arguments =>
    [ { :name => :a },
      { :name => :b },
      { :name => :c, :default => :":b" } ]

Musings right now on how to express certain things.

I think it could be useful to be able to get the symbolic information
for a default parameter (even if it's a method call).

-austin
-- 
Austin Ziegler * halostatue@gmail.com * http://www.halostatue.ca/
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               * austin@zieglers.ca