syntax

Overview ¶

Package syntax parses regular expressions into parse trees and compiles parse trees into programs.

Syntax ¶

This package supports following syntax in addition to the golang built-in regexp.

Grouping:

(?>re)         atomic group; non-capturing
(?=re)         lookahead; non-capturing
(?!re)         negative lookahead; non-capturing
(?<=re)        lookbehind; non-capturing
(?<!re)        negative lookbehind; non-capturing
(?{func})      function call; non-capturing
(?#comment)    comment

Repetitions:

x*+            zero or more x, possessive
x++            one or more x, possessive
x?+            zero or one x, possessive
x{n,m}+        n or n+1 or ... or m x, possessive
x{n,}+         n or more x, possessive
x{n}+          exactly n x, possessive

Back reference:

\kN            refer to numbered capturing
\kName         refer to named capturing
\k{N}          refer to numbered capturing
\k{Name}       refer to named capturing

Lookbehind limitations ¶

Lookbehind and negative lookbehind only support expressions that have deterministic matching length.

(?<=abc)        // OK
(?<=.{2,5})     // OK
(?<=foo|barbaz) // OK
(?<=x+)         // NG