rhaeguard / rgx

a tiny regex engine written in go

rgx

A very simple regex engine written in go. This library is experimental, use it at your own risk!

read the article.

to add the dependency:

go get github.com/rhaeguard/rgx

how to use:

import "github.com/rhaeguard/rgx"

pattern, err := rgx.Compile(regexString)
if err != nil {
	// error handling
}
results := pattern.FindMatches(content)

if results.Matches {
	groupMatchString := results.Groups["group-name"]
}

todo

• ^ beginning of the string
• $ end of the string
• . any single character/wildcard
• bracket notation
  • [ ] bracket notation/ranges
  • [^ ] bracket negation notation
  • better handling of the bracket expressions: e.g., [ab-exy12]
  • special characters in the bracket
    • support escape character
• quantifiers
  • * none or more times
  • + one or more times
  • ? optional
  • {m,n} more than or equal to m and less than equal to n times
• capturing group
  • ( ) capturing group or subexpression
  • \n backreference, e.g, (dog)\1 where n is in [0, 9]
  • \k<name> named backreference, e.g, (?<animal>dog)\k<animal>
  • extracting the string that matches with the regex
• \ escape character
  • support special characters - context dependant
• better error handling in the API
• ability to work on multi-line strings (tested on Alice in Wonderland text corpus)
  • . should not match the newline - \n
  • $ should match the newline - \n
  • multiple full matches

notes

• \ escape turns any next character into a literal, no special combinations such as \d for digits, \b for backspace, etc. are allowed
• numeric groups \n only support single digit references, so \10 will be interpreted as the first capture group followed by a literal 0

credits

• Alice in Wonderland, Lewis Carroll, Project Guttenberg