From 14f6169fcf5c34455c21ca80850eeb5652a85e4a Mon Sep 17 00:00:00 2001
From: William Carroll <wpcarro@gmail.com>
Date: Fri, 13 Nov 2020 16:55:39 +0000
Subject: Document subset of BNF for regex engine

Adding some documentation for my future self.
---
 scratch/facebook/parsing/regex.py | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'scratch/facebook/parsing/regex.py')

diff --git a/scratch/facebook/parsing/regex.py b/scratch/facebook/parsing/regex.py
index e0757e1f788f..7fc2ef34e2ff 100644
--- a/scratch/facebook/parsing/regex.py
+++ b/scratch/facebook/parsing/regex.py
@@ -3,6 +3,16 @@
 #   - parser
 #   - compiler
 # ...for regex.
+#
+# BNF
+# expression -> ( char_class | CHAR ) quantifier? ( "|" expression )*
+# char_class -> "[" CHAR+ "]"
+# quantifier -> "?" | "*" | "+" | "{" INT? "," INT? "}"
+#
+# Of the numerous things I do not support, here are a few items of which I'm
+# aware:
+#   - alternatives:   (a|b)
+#   - capture groups: (ab)cd
 
 from parser import Parser
 import string
-- 
cgit 1.4.1