Automaton
. Regular expressions are built from the following abstract syntax:
regexp | ::= | unionexp | ||
| | ||||
unionexp | ::= | interexp | unionexp | (union) | |
| | interexp | |||
interexp | ::= | concatexp & interexp | (intersection) | [OPTIONAL] |
| | concatexp | |||
concatexp | ::= | repeatexp concatexp | (concatenation) | |
| | repeatexp | |||
repeatexp | ::= | repeatexp ? | (zero or one occurrence) | |
| | repeatexp * | (zero or more occurrences) | ||
| | repeatexp + | (one or more occurrences) | ||
| | repeatexp {n} | (n occurrences) | ||
| | repeatexp {n,} | (n or more occurrences) | ||
| | repeatexp {n,m} | (n to m occurrences, including both) | ||
| | complexp | |||
complexp | ::= | ~ complexp | (complement) | [OPTIONAL] |
| | charclassexp | |||
charclassexp | ::= | [ charclasses ] | (character class) | |
| | [^ charclasses ] | (negated character class) | ||
| | simpleexp | |||
charclasses | ::= | charclass charclasses | ||
| | charclass | |||
charclass | ::= | charexp - charexp | (character range, including end-points) | |
| | charexp | |||
simpleexp | ::= | charexp | ||
| | . | (any single character) | ||
| | # | (the empty language) | [OPTIONAL] | |
| | @ | (any string) | [OPTIONAL] | |
| | " <Unicode string without double-quotes> " | (a string) | ||
| | ( ) | (the empty string) | ||
| | ( unionexp ) | (precedence override) | ||
| | < <identifier> > | (named automaton) | [OPTIONAL] | |
| | <n-m> | (numerical interval) | [OPTIONAL] | |
charexp | ::= | <Unicode character> | (a single non-reserved character) | |
| | \ <Unicode character> | (a single character) |
The productions marked [OPTIONAL] are only allowed if specified by the syntax flags passed to the RegExp
constructor. The reserved characters used in the (enabled) syntax must be escaped with backslash (\) or double-quotes ("..."). (In contrast to other regexp syntaxes, this is required also in character classes.) Be aware that dash (-) has a special meaning in charclass expressions. An identifier is a string not containing right angle bracket (>) or dash (-). Numerical intervals are specified by non-negative decimal integers and include both end points, and if n and m have the same number of digits, then the conforming strings must have that length (i.e. prefixed by 0's). @lucene.experimental