From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-06-11T02:05:47+09:00
Subject: Re: duck-typing allows deeper polymorphism

On Sat, 11 Jun 2005 twifkak@comcast.net wrote:

>>> Not entirely true... The argument 'x' must also respond to whatever
>>> parseargs wants from it (respond_to?, I assume), whatever the 'pa.x' method
>>> wants from it (well, nothing, I assume), and whatever 'p' wants from it
>>> (to_s, I assume).
>>
>> sure - everything in :ducktype=>list AND what parseargs needs - quite true.
> Not just parseargs, but any other methods that the method calls. In your case, it was simply p, but in some other case, I might be passing a parameter all around the system, in which case, who knows what it'll need. (Is that bad design? If so, that's precisely one of the things I want to flesh out as an extra restriction we need to place on ourselves because we're using Ruby.)
>
>>>> note that this could be parsed via rdoc quite easily.
>>> Only if it's an Array literal being passed to parseargs.
>> huh?
> def method(*argv)
>  pa = parseargs(argv){
>    arg :x, :ducktype => File.new('methods.txt').readlines.each { |line|
>      line.chomp
>    }
>  }
>  p pa.x.upcase.downcase
> end

ah.  true true.  at least the docs could show the rhs of the '=>' sign which
would, in 99% of cases, but quite informative.


cheers.

-a
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