Re:Building a Regex Engine in Fewer Than 40 Lines of Code
by ridiculous_fish on Tuesday December 05, 2017 @04:02AM
(#15850663)
I've written a JS regexp parser and engine. It did not fit in 40 lines.
The most obnoxious part is backreferences. The atom \3 is a backreference if the whole regexp contains at least 3 capture groups; otherwise it is an octal (!) escape for char code 3. But you don't know how many capture groups there are until you're done parsing. This is why JS regexp parsers sometimes must make two passes!
The most obnoxious part is backreferences. The atom \3 is a backreference if the whole regexp contains at least 3 capture groups; otherwise it is an octal (!) escape for char code 3. But you don't know how many capture groups there are until you're done parsing. This is why JS regexp parsers sometimes must make two passes!