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From: "Matthew Heaney" <mheaney@on2.com>
Newsgroups: comp.lang.ada
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Subject: Re: Ada Popularity: Comparison of Ada/Charles with C++ STL (and Perl)
Date: Fri, 24 Sep 2004 16:14:48 -0400
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"Kevin Cline" <kevin.cline@gmail.com> wrote in message
news:e749549b.0409240828.53001e66@posting.google.com...
>
> In C++ you can write ++concordance[word] because of two features
> present in C++ that are missing in Ada.  C++ allows the indexing
> operator [] to be overridden, so that concordance[key] can be assigned
> a meaning.  Also, C++ has reference types, so that concordance[key]
> can return a modifiable reference to the value, which can be
> incremented.  Together, these functions allow user-defined types in
> C++ to be as convenient to use as the built-in array type.

Note that (as Randy alluded to) there's still a chance the ARG will add
something like reference types to Ada.  It would be declared something like:

   function Update_Element
     (Container : in Map;
      Key         : in  Key_Type) return access Element_Type;

Then you could say:

   Update_Element (M, K).all := 42;

In our wordcount example you'd have to say:

declare
   N : Natural renames Update_Element (M, K).all;
begin
   N := N + 1;
end;

Note that it would possible to get the automatic insertion behavior too, by
passing the container as an access parameter:

   function Update_Element
    (Container : access Map;
     Key         : in Key_Type) return access Element_Type;

and then say:

declare
   N : Natural renames Update_Element (M'Access, K).all;
begin
   N := N + 1;
end;