From: Charles Oliver Nutter <charles.nutter@...>
Date: 2008-11-14T15:30:44+09:00
Subject: [ruby-core:19928] Re: {Proc,Method}#parameters (Re: Proposal: Method#get_args)

Nobuyoshi Nakada wrote:
> Hi,
> 
> At Thu, 13 Nov 2008 18:44:53 +0900,
> Brian Candler wrote in [ruby-core:19915]:
>> That does give me an idea. Since "?" is not legal in a variable name, then a
>> very simple option could be
>>
>>    def foo(a, b, c=123, d=nil, *e, &blk)
>>
>>      => ["a", "b", "?c", "?d", "*e", "&blk"]
> 
> It's simplest.

The original proposal also asked for literal defaults to be present. I'm 
not sure that's possible with this version. I think I like a version 
that doesn't require examining/mutating the string as well.

With this:

[[:req, 'a'], [:opt, 'b', 1]]

Building a list of params is a simple matter of...

params.each do |p|
   case p[0]
   when :req
     # do something with p[1]
   ...

...and creates no new objects at all.

With the encoded string version, it would require:

params.each do |p|
   case p[0] # new single-char string
   when '?'
     name = p[1..-1] # new string has to be sliced out
   ...
   else
     # else case to handle required args with no leading char...
     # == slowest possible processing for most common case
     name = p
   end
end

The first version is lighter-weight and the cases can be ordered to 
favor the common case of required args.

>>    define_method(:bar) { |a,(b,c)|    }
>>
>>      => ["a", ["b", "c"]]
> 
> Is it really necessary?

I have doubts myself, but I won't vote one way or another.

- Charlie