Re: Using a string as a binary operator

["Jeffrey R. Carter" <spam.jrcarter.not@spam.acm.org>]

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:

The short answer is that you can't. You have to evaluate "1" and "2" to get 
values of some numeric type and push them on a stack, then find a branch in an 
if-elsif-else chain that matches your operator string, and in that branch pop 
the operands and apply the appropriate operator to them. See 
PragmARC.Postfix_Calculator for an (Ada-95) example.

http://pragmada.home.mchsi.com/

-- 
Jeff Carter
"Every sperm is sacred."
Monty Python's the Meaning of Life
55