RE Parser

RE parser provides a simple API to regular expression parsing. It is also able to convert a regular expression into a NFA or a DFA and produce dot files from it.

Building RE parser

From the re_parser directory:

make all

RE parser in command line

RE parser can be used as a command line tool to generate NFA and DFA dot files from a regular expression:

./re_parser "a(b|c)+d*"

Will produce the two files nfa.dot and dfa.dot.

These can be directly viwed with xdot:

xdot nfa.dot
xdot dfa.dot

Or translated to png images with dot:

dot -Tpng -onfa.png nfa.dot
dot -Tpng -odfa.png dfa.dot

See man dot for available formats.

RE parser as a web app

RE parser comes with a web app that allow users to submit regular expression and see the resulting NFA and DFA.

To run the web app server:

./re_app --host localhost --port 3000

The server will be available at http://localhost:3000.

RE parser as a library

You can also use RE parser as a library by importing re_parser.

import re_parser

var re = "a(b|c)+d*"

# Parse re
var re_parser = new REParser
var node = re_parser.parse_re(re)

if node == null then
    print re_parser.last_error.as(not null)
    exit 1
    abort
end

# Build NFA and DFA
var nfa = re_parser.make_nfa(node)
print nfa.to_dot(false)
print nfa.to_dfa.to_dot(false)

Use to_dot(true) to merge transitions on characters.