functional regex engine in python by psykotic of reddit

gistfile1.txt

from itertools import chain

def nil(s):
    yield s

def seq(l, r): 
    return lambda s: (sr for sl in l(s) for sr in r(sl))

def alt(l, r): 
    return lambda s: chain(l(s), r(s))

def star(e):
    return lambda s: chain(nil(s), seq(e, star(e))(s))

def plus(e):
    return seq(e, star(e))

def char(c):
    def match(s):        
        if s and s[0] == c: yield s[1:]
    return match

# c(a|d)+
re = seq(char('c'), seq(plus(alt(char('a'), char('d'))), char('r')))
import sys 
s = sys.stdin.readline()[:-1]
for r in e(s): print "Match with remainder:", r