152
Chapter 7: Using Regular Expressions in Functions
Using backreferences
You use parenthesis to group components of a regular expression into subexpressions. For
example, the regular expression "(ha)+" matches one or more occurrences of the string "ha".
ColdFusion performs an additional operation when using subexpressions; it automatically saves
the characters in the search string matched by a subexpression for later use within the regular
expression. Referencing the saved subexpression text is called
backreferencing
.
You can use backreferencing when searching for repeated words in a string, such as “the the” or “is
is”. The following example uses backreferencing to find all repeated words in the search string and
replace them with an asterisk:
REReplace("There is is coffee in the the kitchen",
"
[ ]+([A-Za-z]+)[ ]+\1
"," * ","ALL")
Using this regular expression, ColdFusion detects the two occurrences of "is" as well as the two
occurrences of "the", replaces them with an asterisk enclosed in spaces, and returns the following
string:
There * coffee in * kitchen
You interpret the regular expression [ ]+([A-Za-z]+)[ ]+\1 as follows:
Use the subexpression ([A-Za-z]+) to search for character strings consisting of one or more letters,
enclosed by one or more spaces, [ ]+, followed by the same character string that matched the first
subexpression, \1.
You reference the matched characters of a subexpression using a slash followed by a digit
n
(\
n
)
where the first subexpression in a regular expression is referenced as \1, the second as \2, etc. The
next section includes an example using multiple backreferences.
:alnum:
Any alphanumeric character. Same as \w.
:xdigit:
Any hexadecimal digit. Same as [0-9A-Fa-f].
:blank:
Space or a tab.
:space:
Any whitespace character. Same as \s.
:print:
Any alphanumeric, punctuation, or space character.
:punct:
Any punctuation character
:graph:
Any alphanumeric or punctuation character.
:cntrl:
Any character not part of the character classes [:upper:], [:lower:], [:alpha:],
[:digit:], [:punct:], [:graph:], [:print:], or [:xdigit:].
:word:
Any alphanumeric character, plus the underscore (_)
ascii
The ASCII characters, in the Hexadecimal range 0 - 7F
Character class Matches
Содержание ColdFusion MX
Страница 1: ...Developing ColdFusion MX Applications...
Страница 22: ...22 Contents...
Страница 38: ......
Страница 52: ...52 Chapter 2 Elements of CFML...
Страница 162: ......
Страница 218: ...218 Chapter 10 Writing and Calling User Defined Functions...
Страница 250: ...250 Chapter 11 Building and Using ColdFusion Components...
Страница 264: ...264 Chapter 12 Building Custom CFXAPI Tags...
Страница 266: ......
Страница 314: ...314 Chapter 14 Handling Errors...
Страница 344: ...344 Chapter 15 Using Persistent Data and Locking...
Страница 349: ...About user security 349...
Страница 357: ...Security scenarios 357...
Страница 370: ...370 Chapter 16 Securing Applications...
Страница 388: ...388 Chapter 17 Developing Globalized Applications...
Страница 408: ...408 Chapter 18 Debugging and Troubleshooting Applications...
Страница 410: ......
Страница 426: ...426 Chapter 19 Introduction to Databases and SQL...
Страница 476: ...476 Chapter 22 Using Query of Queries...
Страница 534: ...534 Chapter 24 Building a Search Interface...
Страница 556: ...556 Chapter 25 Using Verity Search Expressions...
Страница 558: ......
Страница 582: ...582 Chapter 26 Retrieving and Formatting Data...
Страница 668: ......
Страница 734: ...734 Chapter 32 Using Web Services...
Страница 760: ...760 Chapter 33 Integrating J2EE and Java Elements in CFML Applications...
Страница 786: ...786 Chapter 34 Integrating COM and CORBA Objects in CFML Applications...
Страница 788: ......
Страница 806: ...806 Chapter 35 Sending and Receiving E Mail...