Regular expressions in C#   

I am using the .NET regular expressions library to match anything that
resembles a price/amount (33.33, 225.44 etc) out of a stream.  I have
this pattern with me currently:

\d+(\.\d*)?

This doesn't match the string as one full word.  IOW, I want the regex
to match a dollar amount in its entirety (any number of digits before
the decimal point but only 2 digits after the decimal).  I am a total
newbie to Regex and the best I came up with matches even things like
33a.67b (i.e it matches the 33 and 67 in that string whereas I want to
ignore that case completely).

Can someone help?

date: Tue, 22 Jul 2008 10:32:53 -0700 (PDT)   author:   Dilip

Re: Regular expressions in C#   

On Jul 22, 12:32 pm, Dilip  wrote:
> I am using the .NET regular expressions library to match anything that
> resembles a price/amount (33.33, 225.44 etc) out of a stream.  I have
> this pattern with me currently:
>
> \d(\.\d*)?

Ok, so this is the best I have come up with:

(\d[,.]\d\d?)

Any downsides to this?  I used the ',' because not all international
currencies use '.' as the decimal point to represent price.

date: Tue, 22 Jul 2008 10:56:51 -0700 (PDT)   author:   Dilip

Re: Regular expressions in C#   

I found this in the Help:

// Define a regular expression for currency values.
Regex rx = new Regex(@"^-?\d+(\.\d{2})?$");

I don't know what it means, though. It looks like jibberish! :)

"Dilip" wrote:

> On Jul 22, 12:32 pm, Dilip  wrote:
> > I am using the .NET regular expressions library to match anything that
> > resembles a price/amount (33.33, 225.44 etc) out of a stream.  I have
> > this pattern with me currently:
> >
> > \d+(\.\d*)?
> 
> Ok, so this is the best I have come up with:
> 
> (\d+[,+.]\d+\d+?)
> 
> Any downsides to this?  I used the ',' because not all international
> currencies use '.' as the decimal point to represent price.
>

date: Tue, 22 Jul 2008 13:15:27 -0700   author:   jp2msft

Re: Regular expressions in C#   

Dilip wrote:
> On Jul 22, 12:32 pm, Dilip  wrote:
>> I am using the .NET regular expressions library to match anything that
>> resembles a price/amount (33.33, 225.44 etc) out of a stream.  I have
>> this pattern with me currently:
>>
>> \d+(\.\d*)?
> 
> Ok, so this is the best I have come up with:
> 
> (\d+[,+.]\d+\d+?)
> 
> Any downsides to this?

Yes, it would also match strings like:

1+00
1.00000000000000
1+00000000000

> I used the ',' because not all international
> currencies use '.' as the decimal point to represent price.

You will have some better luck with:

^(\d+(?:[,.]\d{2})?)$

^ = start of string
\d+ = at least one digit
(?: = non-catching parenthesis
[,.] = comma or period
\d{2} = exactly two digits
)? = content of parenthesis is optional
$ = end of string

This will match strings like:

1
1.23
1,23
1234
1234.56
1234,56

If you are not matching a complete string, but searching for occurances 
within a string, just remove ^ and $.

-- 
Göran Andersson
_____
http://www.guffa.com

date: Tue, 22 Jul 2008 23:22:59 +0200   author:   Göran Andersson

Re: Regular expressions in C#   

jp2msft wrote:
> I found this in the Help:
> 
> // Define a regular expression for currency values.
> Regex rx = new Regex(@"^-?\d+(\.\d{2})?$");
> 
> I don't know what it means, though. It looks like jibberish! :)

^             start
-?            optional sign
\d+           one or more digits
(\.\d{2})?    optional a period followed by two digits
$             end

Arne

date: Tue, 22 Jul 2008 17:40:56 -0400   author:   Arne Vajhøj

Re: Regular expressions in C#   

On Jul 22, 4:22 pm, Göran Andersson  wrote:
> Dilip wrote:
> > On Jul 22, 12:32 pm, Dilip  wrote:
> >> I am using the .NET regular expressions library to match anything that
> >> resembles a price/amount (33.33, 225.44 etc) out of a stream.  I have
> >> this pattern with me currently:
>
> >> \d(\.\d*)?
>
> > Ok, so this is the best I have come up with:
>
> > (\d[,.]\d\d?)
>
> > Any downsides to this?
>
> Yes, it would also match strings like:
>
> 1
> 1.00000000000000
> 1퍍㓓䴴퍍
>
> > I used the ',' because not all international
> > currencies use '.' as the decimal point to represent price.
>
> You will have some better luck with:
>
> ^(\d(?:[,.]\d{2})?)$

Goran
Thank you very much.  This was very helpful.  I don't use regular
expressions a whole lot in my line of work and didnt' want to read an
entire book to match a trivial pattern like this.

date: Wed, 23 Jul 2008 08:15:35 -0700 (PDT)   author:   Dilip