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Full-fledged "Not" clause in Regular Expressions

Posted on 2008-06-14
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I am using using regular expressions in VB (reference "Microsoft VBScript Regular Expressions 5.5"), but I include Unix developers in the conversation since Unix developers use Regular Expressions so extensively.  I hope that the answer provided is true for the genre of Regular Expressions and not application specific.
Given my research into regular expressions, I have not found a "Not" clause in Regular expressions that applies for more than single characters.  
For example, say that you want to capture the entire string for people whose names appear right after a left curly bracket ("{"), and you want to capture the text between the two curly brackets, with the exclusion of two people, Bob and Roberta.  How do you do it?  
Inside square brackets, the carot symbol ("^") indicates "Not" for whatever else appears within the brackets; but outside the sqare brackets, the same symbol represents the start of the string.  In the code snippet below, I have used the carot symbol twice: the first time incorrectly (not "Bob" nor "Roberta") and the second time correctly (not a right curly bracket).  
Given that my first use of the carot for "Not" is incorrect, can I legitimatly single out Bob and Roberta for exclusion?
Thanks, ~Peter Ferber


"{(^(Bob|Roberta)[^}]+)}"

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Question by:PeterFrb
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Expert Comment

by:ddrudik
ID: 21786355
Supply an example of a source text string, and what it should match.
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Author Comment

by:PeterFrb
ID: 21786395
OK:
     "{John Smith is here!}" --> "John Smith is here!"
     "{Doug Kinsey makes hay.}" --> "Doug Kinsey makes hay."
     "{Bob is my guy.}" --> No match.
     "{Roberta did not show up.}" --> No match.
~Peter
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by:ddrudik
ID: 21786647
You'll have to remove the leading { since vbscript regexes do not support (?<=) constructs:
Raw Match Pattern:
\{(?:(?!\b(?:Bob|Roberta)\b).)*(?=\})
 
$matches Array:
(
    [0] => Array
        (
            [0] => {John Smith is here!
            [1] => {Doug Kinsey makes hay.
        )
 
)

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Accepted Solution

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ahoffmann earned 2000 total points
ID: 21791697
> For example, say that you want to capture the entire string for people whose names appear right after a left curly bracket ("{"), and you want to capture the text between the two curly brackets, with the exclusion of two people, Bob and Roberta.  How do you do it?  

raw regex (assuming that Bobby is valid):

\{((?!(?:Bob|Roberta)).*)\}

following should also work:

\{((?!Bob)(?!Roberta).*)\}
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Author Comment

by:PeterFrb
ID: 21796646
Thank you for these answers.  I have a bit on my plate today, and I promise to give your answers a try either by end of day or Tuesday morning and, if they work, will assign credit.  Sorry for the delay, and thanks for your patience.
~Peter
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Author Closing Comment

by:PeterFrb
ID: 31486063
Superb answer.  Sorry I was delayed in getting back to this.  I just checked the work against the four items we chose, and it was spot on!  Good work.
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