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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Using a string as a binary operator
Newsgroups: comp.lang.ada
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Date: Tue, 14 Oct 2008 19:05:40 +0200
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Date: 2008-10-14T19:05:43+02:00
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On Tue, 14 Oct 2008 08:35:23 -0700 (PDT), Joe wrote:

> I'm trying to build a simple stack the evaluates expressions in
> postfix notation (i.e. "1 2 +").  I can't find a way to use the
> operator directly when I get to it.  When I get to the  "+", but how
> do I apply this string to 1 and 2?  The best I can do is make a case
> statement that has a case for each binary operator, but this seems
> very klunky.  I know you can write "+"(1,2) to return 3 but how do I
> get Ada to recognize the string as an operator?  Here's a short
> example of what I would like to do:
> 
> with Ada.Integer_Text_IO;  use Ada.Integer_Text_IO;
> procedure Operators is
>    Plus : String := "+";
> begin
>    Put( Plus(1,2));
> end Operators;

with Ada.Integer_Text_IO;  use Ada.Integer_Text_IO;
procedure Operators is
   function Plus (L, R : Integer) return Integer renames "+";
begin
   Put (Plus (1, 2));
end Operators;

P.S. I am quite sure that this is not what you need. You don't need strings
in order to evaluate an expression. Evaluation of an expression /= parsing
an expression. It is unclear which one you actually want, or maybe both.

P.P.S. Ada does not "recognize strings as operators." "+" when used to
declare or reference + is technically not a string. It is a string literal.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de