Regular expression question

[David McCollough]

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

XXXXXXXXXXXXXXX X
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]

Re: Regular expression question

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:[color=blue]
> I am trying to formulate a regular expression that would not allow strings
> such as the following to be entered.
>
> XXXXXXXXXXXXXXX X
> 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 ?[/color]

[Karl Seguin [MVP]]

Re: Regular expression question

(.)\1{2}

if you prefer named captures, you can do:

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

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

Karl

--
MY ASP.Net tutorials

http://www.openmymind.net/

"David McCollough" <david.mccollou gh@newsgroups.n ospam> wrote in message
news:92F3CF39-B846-44D8-9B49-43908AC8A81C@mi crosoft.com...[color=blue]
>I am trying to formulate a regular expression that would not allow strings
> such as the following to be entered.
>
> XXXXXXXXXXXXXXX X
> 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 ?[/color]

[David McCollough]

Re: Regular expression question

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 ??

"John Murray" wrote:
[color=blue]
> 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:[color=green]
> > I am trying to formulate a regular expression that would not allow strings
> > such as the following to be entered.
> >
> > XXXXXXXXXXXXXXX X
> > 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 ?[/color]
>[/color]

[Karl Seguin [MVP]]

Re: Regular expression question

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/

"David McCollough" <david.mccollou gh@newsgroups.n ospam> wrote in message
news:50A814DA-140B-478E-8C64-AA4F89CE3DDA@mi crosoft.com...[color=blue]
> 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 ??
>
> "John Murray" wrote:
>[color=green]
>> 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:[color=darkred]
>> > I am trying to formulate a regular expression that would not allow
>> > strings
>> > such as the following to be entered.
>> >
>> > XXXXXXXXXXXXXXX X
>> > 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 ?[/color]
>>[/color][/color]

[Michael Bray]

Re: Regular expression question

John Murray <jmurray@pluck. com> wrote in news:#xgjynGHGH A.1028
@TK2MSFTNGP11.p hx.gbl:
[color=blue]
> You can use backreferencing to do this..... here is an example that
> might do what you want...
>
> ([a-zA-Z])\1{2,}
>
>[/color]

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

-mdb

[David McCollough]

Re: Regular expression question

Thanks for the help.

"Karl Seguin [MVP]" wrote:
[color=blue]
> 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/
>
>
> "David McCollough" <david.mccollou gh@newsgroups.n ospam> wrote in message
> news:50A814DA-140B-478E-8C64-AA4F89CE3DDA@mi crosoft.com...[color=green]
> > 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 ??
> >
> > "John Murray" wrote:
> >[color=darkred]
> >> 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.
> >> >
> >> > XXXXXXXXXXXXXXX X
> >> > 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 ?
> >>[/color][/color]
>
>
>[/color]

[Karl Seguin [MVP]]

Re: Regular expression question

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

karl

--
MY ASP.Net tutorials

http://www.openmymind.net/

"Michael Bray" <mbray@makeDInt oDot_ctiusaDcom > wrote in message
news:Xns9751605 42AB99mbrayctiu sacom@207.46.24 8.16...[color=blue]
> John Murray <jmurray@pluck. com> wrote in news:#xgjynGHGH A.1028
> @TK2MSFTNGP11.p hx.gbl:
>[color=green]
>> You can use backreferencing to do this..... here is an example that
>> might do what you want...
>>
>> ([a-zA-Z])\1{2,}
>>
>>[/color]
>
> Wouldn't that make it so there couldn't be THREE in a row?
>
> -mdb[/color]

[Michael Bray]

Re: Regular expression question

"Karl Seguin [MVP]" <karl REMOVE @ REMOVE openmymind REMOVEMETOO . ANDME
net> wrote in news:ORZVqedHGH A.2940@tk2msftn gp13.phx.gbl:
[color=blue]
> that's what was asked for (greater than 2)
>[/color]

you're right - my bad.

-mdb