The SEQ_REGEXP
rule is similar to the
SEQ
rule except the match sequence is taken to be
a regular expression. In addition to the attributes supported by
the SEQ
tag, the following attributes are supported:
HASH_CHAR
- a literal string which must be at the start of a regular expression.
HASH_CHARS
- a list of possible literal characters, one of which must match at the start of the regular expression.
HASH_CHAR
and HASH_CHARS
attributes are both optional, but you may only specify one, not both. If
both are specified, HASH_CHARS
is ignored and an error
is shown. Whenever possible, use a
literal prefix to specify a SEQ_REGEXP
. If the
starting prefix is always the same, use HASH_CHAR
and provide as much prefix as possible. Only in rare cases would you omit
both attributes, such as the case where there is no other reliable way to get
the highlighting you need, for example, with comments in the Cobol
programming language.
The regular expression match cannot span more than one line.
Regular expression syntax is described in Appendix E, Regular Expressions.
NOTE: c-style character escaping for literals (such as the tab char: \t) do not work as attribute values in XML. Use the XML character entity instead. For example: 	 instead of \t.
Here is a SEQ_REGEXP
rule from moin.xml that uses the HASH_CHARS
attribute, to describe a keyword (wikiword) that can start with any uppercase letter and contain lower case letters and at least one uppercase letter in the middle.
<SEQ_REGEXP HASH_CHARS="ABCDEFGHIJKLMNOPQRSTUVWXYZ" AT_WORD_START="TRUE" TYPE="KEYWORD2">[A-Z][a-z]+[A-Z][a-zA-Z]+</SEQ_REGEXP>