From: Dave Thomas <Dave@...>
Date: 2001-10-25T22:00:23+09:00
Subject: [ruby-talk:23287] Re: Ruby macros

"Aleksei Guzev" <aleksei.guzev@bigfoot.com> writes:

> Parameterized classes are "object-oriented macros" ;)
> Macros are not needed while one can pass a class to a function. 

The original discussion about macros at RubyConf started with some
talk about writing interfaces to web services in Ruby. The problem
there is that you needed to pass to the web services information on
the intended types of parameters, along with the return type of a
method. The 'is' construct came about as a way of doing this:

   def calc_payroll(emp_id is IDL::Integer, name is IDL::String) is IDL::Exported
      ...
   end


or somesuch. As macros, these would allow information on the names and
intended types of parameters to be collected as the method is defined,
but would not affect the underlying syntax of the language too much
(just the addition of the _is_ keyword). In the above example, there
is no typing going on at the Ruby level: all that we've done is help
the IDL stuff generate a typed interface to the outside world.

Once you have this "is" construct, you can keep finding uses for it,
things like

   require "nqxml" is version(:>=, 1.2)

and so on.

I'm not sure how you could do all this with parameterized classes
(tidily).



Dave