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Regular Expression... Evaluator?

I was assigned a project, looks pretty simple but I just don't know where to begin!

In a command window, enter a regular expression...
Then take that RE and change it to a NFA-e, then that NFA-e to NFA, then that NFA to DFA, then that DFA to MDFA... and that result, I should create a file wich I can open in AFER (don't know if you've heard of it...)

Anyways, I need someone to give me a very good push; code is, of course, quite welcome... keep in mind it is strictly c/c++.

Kent Olsen

Hi gabriella_leveron,

This looks like a homework assignment, so I'll nudge a little and you can follow iwht more questions. :)

The first thing that you're going to have to do is "tokenize" the items in the expression. You can grab them "on the fly" from the input stream or build a list. I'd suggest building a list.

TAN(1+SQRT(PI)) /* A meaningless calculation, but a valid example */

Token[0] = "TAN"
Token[1] = "("
Token[2] = "1"
Token[3] = "+"
etc...

Then convert this list of tokens into a tree structure that when perused, accesses the items in NFA-e form.

First we walk, then we run.... :)
Kent

gabriella_leveron

ASKER

I've done Mathematical Expression Evaluators before...

But that is what has me, confused I guess...
When I say RE I mean the user will type in something like (11+0)*(00+1)* and then continue with what i told ya in the original post...

I'm not even crawling with this, dude! If it were a homework assignment, like simple homework, I wouldn't bother posting, I would google.

Kent Olsen

Cool. Then you should be off to a good start. Build the tree such that it can be traversed to produce RPN. From there the only difficulty should be in the understanding of each of the other notations. (Sorry -- I don't know them all.)

Kent

andrewjb

Do you want to actually write the code, or just produce the outcome? The boost library has RE handling routines which I think are quite flexible..

Cayce

Check out this link:

http://www.undu.com/Articles/021016.html

It shows how to use the Microsoft VBScript Regular Expression library in Delphi. The procedure to use it under BCB is the same (just the code changes from Pascal to C++, no big deal). This library comes with almost every version of windows.

gabriella_leveron

ASKER

I actually have to write the code for it :S

Cayce

So, is it homework/school project or not?

ASKER CERTIFIED SOLUTION

Cayce

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