MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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150 Chapter 7: Using Regular Expressions in Functions
You must be aware of the following considerations when using special characters in character sets,
such as [a-z]:
•
To include a hyphen (-) in the square brackets of a character set as a literal character, you
cannot escape it as you can other special characters because ColdFusion always interprets a
hyphen as a range indicator. Therefore, if you use a literal hyphen in a character set, make it
the last character in the set.
•
To include a closing square bracket (]) in the character set, escape it with a backslash, as in [1-
3\]A-z]. You do not have to escape the ] character outside of the character set designator.
Using escape sequences
Escape sequences are special characters in regular expressions preceded by a backslash (\). You
typically use escape sequences to represent special characters within a regular expression. For
example, the escape sequence \t represents a tab character within the regular expression, and the
\d escape sequence specifies any digit, similar to [0-9]. In ColdFusion the escape sequences are
case-sensitive.
The following table lists the escape sequences supported in ColdFusion:
(?!...) If at the beginning of a regular expression, it specifies to use negative lookahead.
Negative is just like positive lookahead, as specified by (?=...), except that it tests for the
absence of a match.
Lookahead parentheses do not capture text, so backreference numbering will skip over
these groups. For more information on backreferencing, see
“Using backreferences”
on page 152 .
(?:...) If you prefix a subexpression with "?:", ColdFusion performs all operations on the
subexpression except that it will not capture the corresponding text for use with a back
reference.
Escape
Sequence Description
\b Specifies a boundary defined by a transition from an alphanumeric character to a
nonalphanumeric character, or from a nonalphanumeric character to an alphanumeric
character.
For example, the string " Big" contains boundary defined by the space
(nonalphanumeric character) and the "B" (alphanumeric character).
The following example uses the \b escape sequence in a regular expression to locate
the string "Big" at the end of the search string and not the fragment "big" inside the
word "ambiguous".
reFindNoCase("\bBig\b", "Don’t be ambiguous about Big.")
<!--- The value of IndexOfOccurrence is 26 --->
When used inside of a character set (e.g. [\b]), it specifies a backspace
\B Specifies a boundary defined by no transition of character type. For example, two
alphanumeric character in a row or two nonalphanumeric character in a row; opposite of
\b.
\A Specifies a beginning of string anchor, much like the ^ special character.
However, unlike ^, you cannot combine \A with (?m) to specify the start of newlines in
the search string.
Special
Character Description