Re: Calculator and Operator Precedence

["Vadim Godunko" <vgodunko@vipmail.ru>]

Hello,

Please send me those sources. Very intresting.

Regards,
Vadim
----- Original Message ----- 
From: "Steven Deller" <deller@smsail.com>
Newsgroups: comp.lang.ada
Sent: Friday, February 22, 2002 7:10 PM
Subject: RE: Calculator and Operator Precedence


> Interestingly, I just cobbled together Ada code to parse arbitrary Ada
> expressions consisting of just operators, parentheses, and literals (I'm
> probably going to make it handle type conversions as well).
> 
> It uses two stacks (one for operands, one for operators), and recursion
> (on parentheses).  Since each stack only needs a maximum of 5 entries
> (because of Ada's left to right evaluation for equal precedence
> operators) they could have been done with simple arrays (though I used a
> stack package abstraction).
> 
> You don't need trees.  
> 
> I thought about using a grammar-based parse (Matthew H's solution), but
> it has some problems with recognizing where you are in the grammar.
> 
> Unary operators are the biggest complication.
> 
> About 50 lines of code.  If you can prove you're not doing a student
> exercise, I'd be glad to send you the sources.
> 
> Regards,
> Steve
>