XQuery

Using Sub-Expressions with Replacement Variables

The replace function allows parenthesized sub-expressions (also known as groups) to be referenced by number in the replacement string. In the $replacement string, you can use the variables $1, $2, $3, etc. to represent (in order) the parenthesized expressions in $pattern. This is very useful when replacing strings on the condition that they come directly before or after another string—for example, if you want to change instances of the word Chap to the word Sec, but only those that are followed by a space and a digit. This technique can also be used to reformat data for presentation. Table 18-16 shows some examples.

get-matches-and-non-matches

The regular expression capabilities of XQuery allow you to determine whether a string matches a regular expression and to replace matches in a string. However, one feature it does not directly provide is the ability to retrieve the parts of a string that do match a pattern. In XSLT 2.0, this can be achieved using the xsl:analyze-string instruction that has no equivalent in XQuery. However, this can be accomplished using the get-matches-and-non-matches function below, which returns a sequence of alternating match and non-match elements containing the strings that do and do not match a pattern. It starts with the entire string, constructs an element depending on whether it begins with a match or nonmatch, and recursively calls itself with the rest of the string.

This function depends on two ...