Re: Inverse regex matching - C# Discussion Boards

10-Jan-08 9:50

Already answered in my previous post (and by Dave in his post)

Sounds like somebody's got a case of the Mondays

-Jeff

Re: A computer name

Dave Kreskowiak10-Jan-08 7:35

Dave Kreskowiak

10-Jan-08 7:35

You might want to not lean on the Enter key when you type your posts...

The only way to change the computer name is to call the Win32 API function SetComputerNameEx[^], or if you just need to change the NetBIOS name, SetComputerName[^]. Changing the computer name requires a restart of the machine for the change to take effect.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007

Inverse regex matching

WillemM10-Jan-08 7:17

WillemM

10-Jan-08 7:17

This one is tricky, that's for sure. I'm looking for a way to generate strings based on a regular expression.
I tried several searches on google and the only stuff that turned up was a library called Grail+ and some perl module genex.

Before I'm going to hack my way into integrating perl into my C# application I want to make sure that I haven't missed a library that does what I need.

Is there anyone who has done this before or knows a library which can help me with this?

WM.

What about weapons of mass-construction?
"What? Its an Apple MacBook Pro. They are sexy!" - Paul Watson
My blog

Skippums10-Jan-08 7:23

10-Jan-08 7:23

Are you just trying to generate random strings that match the regex? What could this possibly be used for? I doubt such functionality is already in the .Net framework, but I am not certain. You could create your own state machine based on a regex, then getting a random string is done trivially by randomly choosing paths from one state to another until you arrive at one of the success states (unless you want to bound or specify the resulting string's length). Anyway, good luck, and let us know if you find a solution elsewhere.

Sounds like somebody's got a case of the Mondays

-Jeff

WillemM11-Jan-08 2:53

WillemM

11-Jan-08 2:53

Indeed, I want to generate random strings that match the regex. I'm generating random data for a database which has some fields that need to match to a specific pattern. I'm pretty sure .NET doesn't have the functionality I'm looking for.

I think creating my own state machine is indeed the best way to go around this, however it's not going to be easy and there is a problem with the max length of strings. I need to find a way to limit the length of the data generated by the * and + operator otherwise this is impossible to do.

Thanks nonetheless

WM.

What about weapons of mass-construction?
"What? Its an Apple MacBook Pro. They are sexy!" - Paul Watson
My blog

Skippums11-Jan-08 4:36

11-Jan-08 4:36

Here is how I would implement it, if I were going to do what you describe (where 'n' is the desired length of the result):

1. Build a directed graph of your regex with nodes==state and edges==allowed state transitions
2. Build a structure containing the number of steps that can be made from
   any one state to any other that is <= the length of your result (2d matrix of lists)
3. Randomly choose an acceptance state (named 'as') where your connectivity matrix
   indicates you can go from the start state to the final state in exactly n transitions.
4. Iterate through the following (initialize cur = startStateNode) until your string is found:
   a. Set 'n' to 'n-1'
   b. Out of all of the nodes reachable from 'cur' in one move,
      eliminate those that can not reach 'as' in 'n' moves
   c. Choose one of the resulting nodes in the collection found in (b)

Once you finish with this process, you will have a randomly generated string matching your regex. Note, however, that strings produced do NOT have equal probability of being chosen. For example, if your regex is, say "(Becky|a\w*)", then "Becky" will result half of the time, whereas words beginning with the letter "a" (this set is clearly much larger) would take the other half. Choosing one at random with equal probability would require you to find ALL matching strings of your given length first, then choosing one of those strings at random (or, you could use graph theory and weight each choice by the number of possible ways to arrive at the destination in the required number of moves). Whatever you decide, I hope you can see that this is clearly not a trivial computation, and it will require a significant (IMO) source of man-hours to code. Good luck,

Sounds like somebody's got a case of the Mondays

-Jeff

If statement not reading gridview row

WillemM11-Jan-08 22:21

WillemM

11-Jan-08 22:21

Thanks for the outline, it got me thinking about how regex parsers are actually build. I found some old material on how to write your own regex parser and I'm going to use that for my library.

My plan is to implement a partial regex parser. This parser will be constructing an NFA of the regex expression and convert it to a DFA.
After that I'm going to determine which parts of the DFA will have a fixed length, those parts will need to be generated first. When these parts are generated I will be filling up the rest of the string with the other variable length parts, starting with the operator + (You need at least one if these) and after that the * operator.

WM.

What about weapons of mass-construction?
"What? Its an Apple MacBook Pro. They are sexy!" - Paul Watson
My blog

TaskDialog?

kumar.bs10-Jan-08 6:10

kumar.bs

10-Jan-08 6:10

Does anybody have sample project of code for creating simple TaskDialogs in framework 2.0, without any unsafe/unmanaged code?

Thanks.

Re: TaskDialog?

Scott Dorman10-Jan-08 7:21

Scott Dorman

10-Jan-08 7:21

If you are referring to the TaskDialog provided by Vista, the only way to do this in .NET is to use interop to the Win32 APIs. There are several examples of how to do that here on CP. There are also some examples that show how to make a TaskDialog-like dialog. Search Results[^]

Scott.

—In just two days, tomorrow will be yesterday.
—Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai

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Member 439056910-Jan-08 6:08

10-Jan-08 6:08

I am trying to read the columns in a selected gridview row. The column value is 760 but when I rund it I get "Blaaaaa". I also tryed doing a while statement before the if statement but that didnt' work either. Below is the code:

public void GridView1_SelectedIndexChanged(Object sender, EventArgs e)
{
GridViewRow row = GridView1.SelectedRow;
string cmopid = row.Cells[1].Text;
string Packageid = row.Cells[2].Text;
string carrier = row.Cells[3].Text;

if (cmopid == "760")
{
Labeltest.Text = "Good to Go";
}
else
{
Labeltest.Text = "Blaaaaaa";
}

}

Skippums10-Jan-08 7:17

10-Jan-08 7:17

change the following line as indicated:

// Original line to be changed
Labeltest.Text = "Blaaaaaa";
// New line after change
Labeltest.Text = string.Format("{0}; {1}; {2}", cmopid, Packageid, carrier);

Then debug by seeing what results you get, and where they are comming from.

Sounds like somebody's got a case of the Mondays

-Jeff

Member 439056910-Jan-08 7:25

10-Jan-08 7:25

I did that and I got the right values:

xxx;sss;zzz

Skippums10-Jan-08 7:35

10-Jan-08 7:35

So it is working?

Sounds like somebody's got a case of the Mondays

-Jeff

Member 439056910-Jan-08 8:14

10-Jan-08 8:14

Well, it does seem to be working but there is something wrong. The first value is 760 so why don't I get "Good to Go".

Skippums10-Jan-08 8:35

10-Jan-08 8:35

My guess is that the value is not really "760". I bet there is an extra character in there, like a space or a tab or something. Check the ".Length" property on the value that looks like it is "760", and I bet it is not 3. If this is correct, then just call the ".Trim()" method on the string prior to comparison to remove extraneous whitespace.

Sounds like somebody's got a case of the Mondays

-Jeff

Member 439056910-Jan-08 8:48