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4GuysFromRolla.com : ASP FAQS : Strings


Is there a way to replace pattens of text in a string so that the replacement text includes whatever the pattern matches? For example: enclose all words ending in "ing" in tags?

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Answer: Regular expressions can help provide the solution. Here is a function that replaces the text matched by a regular expression with whatever you specify. It's syntax is this: RegExpReplace(input, pattern, replacement_text). Input is the string you wish to search and replace, pattern is the regular expression that gets matched and replacement_text is what you want to replace it with. Note that you use <?> to indicate the pattern match.

The first portion of code just sets up some variables and the regular expression:

Function RegExpReplace(strInput, strPattern, strReplace)
    Dim regEx, Match, Matches, Position, strReturn
    Position = 1
    strReturn = ""

    Set regEx = New RegExp
        regEx.Pattern = strPattern
        regEx.IgnoreCase = True
        regEx.Global = True

Next the important part. The For ... Next loop below alternates between adding the matched and non-matched portions of the input string.

    Set Matches = regEx.Execute(strInput)
    For Each Match in Matches
        ' Below line adds everthing from the current position
        ' to the next pattern match
        strReturn = strReturn & Mid(strInput, Position, Match.FirstIndex+1-Position)

        ' Then this line adds the match into the replacement string
        ' and appends it to the result.
        strReturn = strReturn & Replace(strReplace, "<?>", Match.Value)
        Position = Len(Match.Value) + Match.FirstIndex + 1

    ' Add any text after the last match
    strReturn = strReturn & Mid(strInput, Position, Len(strInput))

    RegExpReplace = strReturn
End Function

So the following call: RegExpReplace("Today is a good day.", "\bday\b", "*<?>*") returns: Today is a good *day*.

Or for the example given in the question: RegExpReplace("Going to work is boring.", "\b[^ ]*ing\b", "<?>") returns: Going to work is boring.

FAQ posted by Richard Lowe at 10/17/2000 3:25:08 AM to the Strings category. This FAQ has been viewed 46,427 times.

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Last computed at 9/17/2007 3:22:00 AM

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