Thread: [Dev-C++] Extracting a mathemtical expression

Hello,

I would like to know what is the best way to extract a math expression =
to=20
IF condition.

For instance:
I have in a configuration file an expression X=3DY and I want use the =
expression in IF conditin as it is. So the condition will look like:
IF (x=3Dy( ...

Also would like to know about some XML parser written in C.
I prefer C to C++.
Thank you.

Jan Mura
jan...@vo...
 

>Also would like to know about some XML parser written in C.
=20
http://www.libxml.org
=20
--
Bernd M=FCnt                   Durchwahl: 030/69032-509
euroscript Deutschland GmbH  Zentrale:  030/69032-300
Abteilung IT-Management      Fax:       030/69032-505
Alt-Moabit 91                Mail:      Ber...@eu...
10559 Berlin                 Web:       http://www.euroscript.de =
<http://www.euroscript.de/> =20
=20

Hi,

>I would like to know what is the best way to extract a math expression

The best way I can think of is to create a parser to read the expression. I
would do it using flex and bison, and incorporating the produced parser int=
o
your project.
Flex will chop the input into tokens (more precisely 'lex=E8mes' in french.
not sure in english) based on regular expressions you specify. eg. numbers,
operators...
Bison is usually fed the output from Flex, and matches the tokens to syntax
rules, eg. EXPRESSION: NUMBER OPERATOR NUMBER
Every time bison matches a rule, you can execute some code (usually build a
tree representing the input)

Compilers (maybe not all, but probably) are built this way. The tree is the=
n
analysed, checked, and turned into something useful :D

Building a simple flex file and set of bison rules for just arithmetic
should be simple, and you'll probably be able to find a lot of doc' out
there
The flex/bison programs will parse your spec. files, creating a C or
C++(some hacks required) file you can incorporate into your project.

You can also use flex/bison to parse your config file if you want, while
you're at it :D

Best of luck,

Jonathan


On 4/19/07, Jan Mura <jan...@vo...> wrote:
>
>  Hello,
>
> I would like to know what is the best way to extract a math expression to
> IF condition.
>
> For instance:
> I have in a configuration file an expression X=3DY and I want use the
> expression in IF conditin as it is. So the condition will look like:
> IF (x=3Dy( ...
>
> Also would like to know about some XML parser written in C.
> I prefer C to C++.
> Thank you.
>
> Jan Mura
> jan...@vo...
>
>
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--=20
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