The old regex engine was replaced by boost xpressive in highlight 3.11 - expect minor grammar updates

You can use regular expressions in highlight language definitions. Note that the expression has to be defined in regex(). See Language definitions which definition parameters support regular expressions.

Note that the expression has to be defined as regex(<RE> <, GRUP-NUM>), where RE is the regex string, and GROUP-NUM is an optional parameter which defines the group number whose match should be returned.

The backslash character ('\') serves to introduce escaped constructs, as defined in the table above, as well as to quote characters that otherwise would be interpreted as unescaped constructs. Thus the expression \\ matches a single backslash and \{ matches a left brace.

It is an error to use a backslash prior to any alphabetic character that does not denote an escaped construct; these are reserved for future extensions to the regular-expression language. A backslash may be used prior to a non-alphabetic character regardless of whether that character is part of an unescaped construct.

It is necessary to double backslashes in string literals that represent regular expressions to protect them from interpretation by a compiler. The string literal “\b”, for example, matches a single backspace character when interpreted as a regular expression, while ” \\ b” matches a word boundary. The string litera “\(hello\)” is illegal and leads to a compile-time error; in order to match the string (hello) the string literal ” \\ (hello \\ )” must be used.

Character classes may appear within other character classes, and may be composed by the union operator (implicit) and the intersection operator (&&). The union operator denotes a class that contains every character that is in at least one of its operand classes. The intersection operator denotes a class that contains every character that is in both of its operand classes.

The precedence of character-class operators is as follows, from highest to lowest: - Literal escape \x - Range a-z - Grouping […] - Intersection [a-z&&[aeiou]] - Union [a-e][i-u] Note that a different set of metacharacters are in effect inside a character class than outside a character class. For instance, the regular expression . loses its special meaning inside a character class, while the expression - becomes a range forming metacharacter.

Capturing groups are numbered by counting their opening parentheses from left to right. In the expression

((A)(B(C)))

for example, there are four such groups:

- ((A)(B(C)))
- (A)
- (B(C))
- (C)

Group zero always stands for the entire expression. Note that highlight will only evaluate the highest group number to make regular expressions more suitable for language definitions. Use (?:) syntax to avoid a capture of the new group.

Regex=[[ [A-Z]\w+ ]]

Highlight identifiers beginning with a capital letter.

Regex=[[ [$@%]\w+ ]]

Highlight variables beginning with $, @ or %.

Regex=[[ \$\{(\w+)\}) ]]

or

Regex=[[ \$\{(\w+)\} ]], Group=1

Highlight variable names like ${name}. Only the name is highlighted as keyword. A sub.expression is used to achieve this effect. If no sub-expression number is defined (like in the first example above), the right-most sub match (highest sub id) is returned.

Regex=[[ (\w+)\s*\( ]]

Highlight method names. Note that a sub expression is used again.

Regex=[[STO\xe2\x88\x91]]

Unicode characters in a keyword.