XSLT, 2nd Edition

Simple Expressions

The simplest regular expression is just a string of text. The regular expression abc matches the string abc. We’re merely searching for a series of characters inside some data. For this case, contains('abc', 'abc') does the same thing.

Regular expressions exist to do far more than search for a literal string; they help us find data that matches a pattern. We can use character sets to specify groups of characters. The regular expression [abc]d matches two characters in which the first character is a, b, or c, followed by the character d.

We can also negate a character set, asking for all the characters not in the character set. To do this, add a caret (^) to the start of the character set. The regular expression [^abc]d matches two characters in which the first character is anything except a, b, or c, followed by d.

Ranges give us a shorthand way of defining character sets. The character set [0-9] specifies the digits 0 through 9, while the character set [a-zA-Z] specifies all of the unaccented letters used in Western European languages. A range can be negated just like any other character set; [^0-9] specifies anything except the digits.

Ranges can also be subtracted from each other. The range [A-Z-[IOQ]] matches any unaccented uppercase letter except I, O, or Q.