From: Pit Capitain <pit@...>
Date: 2005-09-20T00:39:42+09:00
Subject: Re: help with tricky proc/binding issue

Ara.T.Howard schrieb:
> 
> i'm trying to be able to define a proc that can be called in the context of
> self, eg:
> 
>   block = lambda{ p 42 }
>   an_obj.instance_eval &block
> 
> but which can also be called with arguments, for example (imaginary ruby):
> 
>   b = lambda{|x| p [x, y]}
> 
>   class C
>     def y; 42; end
>   end
> 
>   c = C::new
>   x = 42
> 
>   c.arg_instance_eval(x, &b)  #=> [42, 42]
> 
> any ideas?

Tom (aka Trans) recently mentioned that he changed procs into methods in 
order to get what you want. Here's a quick hack, not efficient and not 
thread-safe, but maybe a start:

   class Object
     def arg_instance_eval( *args, &block )
       c = class << self; self; end
       c.send( :define_method, :arg_instance_eval_method, &block )
       arg_instance_eval_method( *args )
     ensure
       c.send( :remove_method, :arg_instance_eval_method )
     end
   end

   b = lambda{|x| p [x, y]}

   class C
     def y; 42; end
   end

   c = C::new
   z = 41

   c.arg_instance_eval( z, &b )  # => [41, 42]

Regards,
Pit