how to write a calculator program which obey precedence rules?

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Hi,
I am working on a C++ project that I need help for it.
In this project the program should get a phrase, for example:
7+2*3+4/2
and calculate it. The hard part is that it should obey precedence rules.
And If it can support power and parentheses; I will be better but it is nit nessecary.
Could anyone give me an idea or a hint?
Regards,

Posted 22-Dec-09 23:14pm

FTBina

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Christian Graus · Answer 1 · 2009-12-22T23:18:00

If you want to support precedence, you need to take the entire string and parse it, you can't do it as you go, as you won't know the precedence. So, what you want to write is a string parsing engine that works out the order of precedence as it goes, searching for * and / before applying + and -.

CPallini · Answer 2 · 2009-12-23T00:12:00

Solution 3

You may write your own expression parser (see, for instance [^] or you may use a tool, such flex [^]+bison[^] or ANTLR [^], for this task.
You may even embed a script language (like, for instance Lua [^]) in your application and make it evaluate the expression for you.

Posted 23-Dec-09 0:12am

CPallini

Updated 23-Dec-09 0:13am

v2

Bhasker Kandpal · Answer 3 · 2009-12-22T23:23:00

Solution 2

you have to write an expression parser for it, implementing stack operation.

Posted 22-Dec-09 23:23pm

Bhasker Kandpal