From: Daniel Nugent <nugend@...>
Date: 2006-04-02T10:08:53+09:00
Subject: Re: Typed Parameters

Well, I think you should allowed to put a selective effect on the
remaining arguments, but it should at least allow you to be a little
smarter than simply checking one single Type.  I'd like to see you
able to check against multiple types as well as methods and
combinations thereof, like

def foo(arg1 : (Array and :custom_array_method) or Hash or :special_method)

Then at least it's simply a syntactic convenience for writing
respond_to? and kind_of? calls.  And, logically, you should be able to
assign these parameter checks to a variabe so you can reduce the
duplication of them, although I don't have a clue as to what a good
syntax for that would be... Maybe something like:

type_check = TypeCheck.new do |var|
  case var
  when Array
    return true if var.respond_to? :custom_array_method
  when Hash
    return Hash
  else
    return true if var.respond_to? :special_method
  end
  return false
end

And, of course, you can do any checking you want in the block. You
could then do this:

def foo(arg1 : type_check)
def bar(arg1, arg2 : type_check)

On 4/1/06, Trans <transfire@gmail.com> wrote:
> <blockquote>
> It's not actually that practical, and such things end up making your
> code very much like C++ and Java.
>
> Ruby is smarter than that. Ruby can do more than that.
>
> Think in terms of what your object's required capabilities are instead
> of pretending that a class indicator is sufficient for that.
> </blockquote>
>
> While I understand you pointr Austin --obviously where talking Duck
> Typing here. But I think it is interesting to condier that this is some
> respect antithetical to OOP in general --I mean the reciever _is_ a
> specific type. And that reacieve detemine the functionality of the
> method call. It is sort of as if you were progamming in a more
> traditional functional language and _had_ to specifiy the type of the
> first argument, but never the remaining.
>
>   foofunc(  FooClass foo, clever, smart, stupid )
>
> instead of
>
>   foo.foofunc( clever, smart, stupid )
>
> So why shouldn't any of the other participating objects have a
> selective effect too?
>
> T.
>
>
>


--
-Dan Nugent

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