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obtaining multiple substrings from text using regular expressions

Posted on 2008-10-03
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Last Modified: 2012-05-05
After the success (and ease for which it was answered) of my last regular expression question, I am taking it to the next level. The html code below is part of a larger source page and I want to retrieve two values from a given line without the surrounding junk.

From the code below, I want the regex to produce:

#7 in IV.44

(refer code for the rest of the question)
...
 <tr>
  <td class="column">Battle:</td>
  <td>#7 in <a href='comp.asp?bID=234'>IV.44</a></td>
 </tr>
...
 
#I can get the first part using: #[0-9]\sin
#and the second part using:      [IV]+\.[0-9]+
 
#is there a way I can concatenate these together 
#in the one expression whereby omitting the 
#superfluous link in between?

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Question by:madivad2
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9 Comments
 
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Accepted Solution

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ddrudik earned 500 total points
ID: 22633902
You can use groups:
(#\d\sin).*?([IV]+\.\d+)

Note that [IV]+ matches one or more I,V characters in any order if that's what you wanted.
For each m as Match in mc
        Console.Writeline(m.Groups(1).Value & m.Groups(2).Value)
Next

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Author Comment

by:madivad2
ID: 22634045
I could, but I am trying to avoid using groups at the moment but I simply want to apply the regex and implement it on the fly without additional code.

My primary reason for this is if the format of the page changes I want to be able to change the regular expression in a config file without having to recompile my app to accommodate new groups numbers that may be required.

I was hoping something like your other solution would be possible where the text is omitted from the result: (?<=user'>)[^<]*

Someone how omit the link/url information inbetween
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Expert Comment

by:ddrudik
ID: 22634079
You can't skip over text in the middle of a match without the use of groups.  Another option is is to do a replace, but you are replacing the match with m.Groups(1).Value & m.Groups(2).Value so it's about the same as the above code.
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Author Comment

by:madivad2
ID: 22634262
I just thought I'd clarify, I don't have a problem with groups in the expression, just that I don't want to rely on them in code since the expression can be set outside the application. Can you do an on-the-fly substitution of the undesirable tag?

Also, to clarify an earlier point, the [IV]+ is what I was after, I just didn't explain it well. It is to include all roman numerals from I to VIII
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Expert Comment

by:ddrudik
ID: 22634742
I might not understand what you are asking for, do you want to do a replacement on the string?
Raw Match Pattern:
(#\d\sin).*?([IV]+\.\d+)
 
Capture Groups:
    [0] => #7 in <a href='comp.asp?bID=234'>IV.44
    [1] => #7 in
    [2] => IV.44

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Author Comment

by:madivad2
ID: 22635398
I know the code below is invalid, but this is along the lines of what I am after. I want the middle group to be removed in much the same way you got rid of the beginning of the line when we were searching for userIDs (and left off the userID part at the front)

I am on the verge of just thinking it's not possible, but I am trying to canvass all options
Raw Match Pattern:
(#\d\sin)(?<=.*?)([IV]+\.\d+)  ' I know this is invalid
 
Capture Groups:
    [0] => #7 in IV.44
    [1] => #7 in
    [2] => IV.44

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Expert Comment

by:ddrudik
ID: 22636415
Unfortunately that is invalid, regular expressions do not work in that fashion:
Imports System.Text.RegularExpressions
Module Module1
    Sub Main()
        Dim sourcestring As String = "<td>#7 in <a href='comp.asp?bID=234'>IV.44</a></td>"
        Dim re As Regex = New Regex("(#\d\sin )(?:.*?)([IV]+\.\d+)")
        Dim mc As MatchCollection = re.Matches(sourcestring)
        For Each m As Match In mc
            Console.WriteLine(m.Groups(1).Value & m.Groups(2).Value)
        Next
    End Sub
End Module

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Author Closing Comment

by:madivad2
ID: 31502751
Thanks ddrudik! Although not quite the answer I was looking for (and here I was thinking you were a God), you have come thru once again. Thanks for your efforts! I have taken on board much of what you have given me and I have even succumbed to the groups in my application. Regards
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Expert Comment

by:ddrudik
ID: 22641751
Thanks for the question and the points.
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