Re: Ruby Method Signatures (was Re: Multiton in standard library)

On 3/23/07, Rick DeNatale <[e-mail]> wrote:
> On 3/23/07, TRANS <[e-mail]> wrote:
> > On 3/23/07, Rick DeNatale <[e-mail]> wrote:
>
> > > On reflection though, I don't think that this is a good idea anyway.
> > > Given that Ruby allows dynamic re-definition what should this do?
> > >
> > > def foo(x)
> > >    end
> > >
> > >  def bar(*=method(:foo).signature)
> > >      p x   # or  p a1
> > >   end
> > >
> > >   bar(1)  #=> 1
> > >
> > >   def foo(y)
> > >   end
> > >
> > >   bar(1) #=> ?
> > >
> > > I suppose that the answer is 1, and that the signature is just used as
> > > it is when bar is defined, but then I'm not sure that this is really a
> > > useful feature, it certainly doesn't make the definition of bar EASIER
> > > to read.
> >
> > Thats' true. The real need though is just so we can define method
> > wraps with the same arity. That's the useful part. How else could we
> > go it?
>
> Something like this might work, the only glitch is methods like
> def foo(d=1)  which have an arity of -1 indicating that they  have a
> variable number of arguments, but this doesn't indicate that they have
> an upper limit on the number of arguments.
>
> But I think that it gets close:
>
> module PlistGenerator
>   def plist
>     # the arity is a positive number if all arguments are required
>     # otherwise it is -1-number_of_required arguments
>     # n = -1 - required
>     # required + n = -1
>     # required = -1 -n
>     n = arity
>     req_ct = n >= 0 ? n : -1 - n
>     args = (1..req_ct).map {|num| "a#{num}"}
>     args << "*opt" if n < 0
>     args.join(',')
>   end
> end
>
> class Method
>   include PlistGenerator
> end
>
> class UnboundMethod
>   include PlistGenerator
> end

Yea, That's basically what I've been doing. It would be nice if we had
something more robust though, in the language itself.

Thanks,
T.