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Last active January 21, 2022 14:30
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Regex
Raw
regex.md

Regex

is a very simple esoteric programming language.

The program is of the form

c/filter/flags/halt/flags2 comments

Note that /s in c must be escaped, and special chars in /filter/flags and /halt/flags2 must be escaped, as they are regular expressions and subject to their rules. Flags are case insensitive. Supported flags:

  • n - also consider non-printable characters (if on for any is automatically on for the other)
  • i - case-insensitive
  • m - also consider multiline strings (ditto)
  • l - enable multiline mode, automatically implying m
  • s - dot matches all
  • f - match the entire string
  • x - only a flag in halt, make program run infinitely
  • +group - only print a group (reference by number). Default is equivalent to +0
  • -group - same, but by name In addition, verbose mode is enabled, allowing comments.

Execution

The regex interpreter, if c is preset, takes an input, and then runs through strings, and for each string:

  • If /halt/flags2 matches inputcstring if there is input, or string if there is none, it halts.
  • If /filter/flags matches inputcstring if there is input, or string if there is none, it prints string. It counts using Pyth's base256 encoding.
Raw
regex.py
import re
class RegexSyntaxError(Exception): ...
filter_printable = re.compile("")
def basedecode(n, charset):
if n == 0: return ""
last = n % len(charset)
return basedecode(n // len(charset), charset) + charset[last]
multiline, nonprintable = False, False
def compile(regex, flags, error_context=""):
global multiline, nonprintable
if "n" in flags: nonprintable = True
if "m" in flags or "l" in flags: multiline = True
fg = re.U
if "x" in flags: return lambda x: False
if "i" in flags: fg |= re.IGNORECASE
if "l" in flags: fg |= re.MULTILINE
if "s" in flags: fg |= re.DOTALL
try: result = re.compile(regex, fg)
except re.error as e: raise RegexSyntaxError("Invalid regex in " + error_context + "(/" + regex + "/" + flags + "): " + "\n".join(e.args))
if "f" in flags: return result.fullmatch
return result.match
extraction = re.compile(r"^((?:[^\\/]|\\.)*)/((?:[^\\/]|\\.)*)/([nimsfNIMSF]*)((?:\+[0-9]+)?(?:\-\w+)?)/((?:[^\\/]|\\.)*)/([nimsfxNIMSFX]*)") # ironic
def parse(program):
matches = extraction.match(program)
sep = matches.group(1)
uinput = bool(sep)
filt = compile(matches.group(2), matches.group(3), "filter")
halt = compile(matches.group(5), matches.group(6), "halting")
printing = matches.group(4)
if "+" in printing and "-" in printing: raise RegexSyntaxError("You cannot use two priting modes")
if printing == "": group = 0
elif printing[0] == "+": group = int(printing[1:])
elif printing[0] == "-": group = printing[1:]
return sep, uinput, filt, halt, group
def enum(charset):
i = 0
while True:
yield basedecode(i, charset)
i += 1
def run(regex, get_input=input):
sep, uinput, filt, halt, group = parse(regex)
if uinput: prefix = get_input() + sep
else: prefix = ""
if nonprintable and multiline: charset = [chr(i) for i in range(128)]
if nonprintable and not multiline: charset = [chr(i) for i in range(128) if i != 10]
if not nonprintable and multiline: charset = [10] + [chr(i) for i in range(32, 127)]
if not nonprintable and not multiline: charset = [chr(i) for i in range(32, 127)]
for i in enum(charset):
if halt(prefix + i): return
if filt(prefix + i): yield filt(prefix + i).group(group)
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