Regular expression question

[Guest]

I am trying to formulate a regular expression that would not allow strings
such as the following to be entered.

XXXXXXXXXXXXXXXX
AAAAAAAAAAAAAAA
BBBBBBBBB

Basically any repeating character > 2 of the same character.

I have tried several things and I can't seem to get it to work.

Any suggestions ?

 

[John Murray]

You can use backreferencing to do this..... here is an example that
might do what you want...

([a-zA-Z])\1{2,}

 

[Karl Seguin [MVP]]

(.)\1{2}

if you prefer named captures, you can do:

(?<char>.)\k<char>{2}

in c# you'll need to escape the \ with \\ unless it isn't in codebehind..

Karl

 

[Guest]

John

Thanks so much for the help.

I understand what the [a-zA-Z] does and I understand what the {2,} does.

What does the \1 do ??

You can use backreferencing to do this..... here is an example that
might do what you want...

([a-zA-Z])\1{2,}

I am trying to formulate a regular expression that would not allow strings
such as the following to be entered.

XXXXXXXXXXXXXXXX
AAAAAAAAAAAAAAA
BBBBBBBBB

Basically any repeating character > 2 of the same character.

I have tried several things and I can't seem to get it to work.

Any suggestions ?

 

[Karl Seguin [MVP]]

it's a back reference \1 references the first group capture. A capture is
anything between unescaped parenthesis ( )

Karl
--
MY ASP.Net tutorials
http://www.openmymind.net/

John

Thanks so much for the help.

I understand what the [a-zA-Z] does and I understand what the {2,} does.

What does the \1 do ??

You can use backreferencing to do this..... here is an example that
might do what you want...

([a-zA-Z])\1{2,}

I am trying to formulate a regular expression that would not allow
strings
such as the following to be entered.

XXXXXXXXXXXXXXXX
AAAAAAAAAAAAAAA
BBBBBBBBB

Basically any repeating character > 2 of the same character.

I have tried several things and I can't seem to get it to work.

Any suggestions ?

 

[Michael Bray]

You can use backreferencing to do this..... here is an example that
might do what you want...

([a-zA-Z])\1{2,}

Wouldn't that make it so there couldn't be THREE in a row?

-mdb

 

[Guest]

Thanks for the help.

it's a back reference \1 references the first group capture. A capture is
anything between unescaped parenthesis ( )

Karl
--
MY ASP.Net tutorials
http://www.openmymind.net/

John

Thanks so much for the help.

I understand what the [a-zA-Z] does and I understand what the {2,} does.

What does the \1 do ??

You can use backreferencing to do this..... here is an example that
might do what you want...

([a-zA-Z])\1{2,}


David McCollough wrote:
I am trying to formulate a regular expression that would not allow
strings
such as the following to be entered.

XXXXXXXXXXXXXXXX
AAAAAAAAAAAAAAA
BBBBBBBBB

Basically any repeating character > 2 of the same character.

I have tried several things and I can't seem to get it to work.

Any suggestions ?

 

[Karl Seguin [MVP]]

that's what was asked for (greater than 2)

karl

--
MY ASP.Net tutorials
http://www.openmymind.net/

You can use backreferencing to do this..... here is an example that
might do what you want...

([a-zA-Z])\1{2,}

Wouldn't that make it so there couldn't be THREE in a row?

-mdb

 

[Michael Bray]

"Karl Seguin [MVP]" <karl REMOVE @ REMOVE openmymind REMOVEMETOO . ANDME
net> wrote in

that's what was asked for (greater than 2)

you're right - my bad.

-mdb