lpeg email pattern

gistfile1.lua

local P = lpeg.P
local R = lpeg.R
local S = lpeg.S
local V = lpeg.V
local C = lpeg.C

local CHAR = R"\0\127"
local SPACE = S"\40\32"
local CTL = R"\0\31" + P"127"

local specials = S[=[()<>@,;:\".[]]=]

local atom = (CHAR-specials-SPACE-CTL)^1
local dtext = CHAR - S"[]\\\13"
local qtext = CHAR - S'"\\\13'
local quoted_pair = "\\" * CHAR
local domain_literal = P"[" * ( dtext + quoted_pair )^0 + P"]"
local quoted_string = P'"' * ( qtext + quoted_pair )^0 * P'"'
local word = atom + quoted_string

-- Implements an email "addr-spec" according to RFC822
local email = P {
	V"addr_spec" ;
	addr_spec = V"local_part" * P"@" * C(V"domain") ;
	local_part = word * ( P"." * word )^0 ;
	domain = V"sub_domain" * ( P"." * V"sub_domain" )^0 ;
	sub_domain = V"domain_ref" + domain_literal ;
	domain_ref = atom ;
}