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From: george.priv@gmail.com
Newsgroups: comp.lang.ada
Subject: Re: Using a string as a binary operator
Date: Tue, 14 Oct 2008 15:01:40 -0700 (PDT)
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Date: 2008-10-14T15:01:40-07:00
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On Oct 14, 11:35=A0am, Joe <joesmo...@gmail.com> wrote:
> Hey all,
>
> I'm trying to build a simple stack the evaluates expressions in
> postfix notation (i.e. "1 2 +"). =A0I can't find a way to use the
> operator directly when I get to it. =A0When I get to the =A0"+", but how
> do I apply this string to 1 and 2? =A0The best I can do is make a case
> statement that has a case for each binary operator, but this seems
> very klunky. =A0I know you can write "+"(1,2) to return 3 but how do I
> get Ada to recognize the string as an operator? =A0Here's a short
> example of what I would like to do:
>
> with Ada.Integer_Text_IO; =A0use Ada.Integer_Text_IO;
> procedure Operators is
> =A0 =A0Plus : String :=3D "+";
> begin
> =A0 =A0Put( Plus(1,2));
> end Operators;
>
> Thanks,
> Joe

You are confusing compile time and run time phases of your program's
life.  When you call "+"(a,b), it is treated as any other function
(Could have been Add(a,b)). Ada overload feature allows for more
convenient substitution in form a+b.  The construct is recognized
during compilation of the source code.   At run time compiler is no
longer used and sometimes unavailable.  So you have to write your own
parser that will handle your input string.  There is plentiful code
samples out there on the WEB in variety of languages I am sure.

George.