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

On 3/21/07, Jos Backus <[e-mail]> wrote:
> On 3/19/07, TRANS <[e-mail]> wrote:
> >
> >Which reminds me, it would be nice of Method could return a
> >representation of a methods signature. I've run into this need
> >elsewhere too.
>
> This would be nice for some kinds of tracing. We have a Perl Trace library at
> work which prints the method's arguments, and is used like this:
>
>     su foo {
>       my($arg1, $arg2) = @_;
>       Trace::begin(@_);
>       ...
>     }
>
> No easy way to do this in Ruby beyond
>
>     Trace.begin(arg1, arg2)
>
> Instead I'd like to be able to write
>
>     Trace.begin(__argv__)

I'm a little confused, What's output of this?

This maybe completely aside, but the above reminds me that with
'this', there could be:

  def(a,b)
    Trace.begin(*this.arguments)
  end

Basically args irregardless of the the actual signature.

As for the signature, it would have to be a special class of object
that has the qualities of Ruby's arguments -- the ordered list, the
default params and etc. With that object a few things could be
queried, such as arity, maybe a list of parameter names, whether it
has a * parameter or a &block parameter, etc. Importantly it could
output a string representation or the args (whether with the original
names or not). Eg.

  def a(x,y)
    this.signature.to_s  #=>  "x,y" -or- "a1,a2"

A bonus would be to use the arguments in place of actual arguments
when defining a method.

  def foo(x)
  end

  def bar(*=method(:foo).signature)
    p x   # or  p a1
  end

  bar(1)  #=> 1

The *= is needed b/c there has to a special way to indicate that.

T.