Re: [boost] Making 'any' visitable

From: Vesa Karvonen (vesa_karvonen_at_[hidden])
Date: 2002-04-10 02:58:08

Andrei Alexandrescu:
>I'd like to propose making 'any' visitable. Without visitation, all
>you can do to query the type of any is to do it explicitly, which is
>awkward and error-prone.
>
>With visitation, one can add processing to any that is nicely
>decoupled. (By the way, due to the nature of 'any', it seems like only
>acyclic visitation will do - the classic GoF visitor won't work.)
>
>So, in a nutshell - do you guys think it's a good idea?

A visitor mechanism would be nice. Another desirable feature would be 
pattern matching to allow inspecting any objects:

  switch_(an_any)
  [ case_<int>   ( a_function_like_object_of_one_int_parameter )
  | case_<float> ( a_function_like_object_of_one_float_parameter )
  | default_     ( a_function_like_object_of_zero_parameters )
  ]

The function like objects could then be implemented using the lambda 
library, for instance.

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