Is there a regular expression to detect a valid regular expression? (2008)
1–10 of 13 posts
Re: Is there a regular expression to detect a valid regular expression? (2008)
#2Related:
Is there a regular expression to detect a valid regular expression? - https://news.ycombinator.com/item?id=20909939 - Sept 2019 (219 comments)
Re: Is there a regular expression to detect a valid regular expression? (2008)
#3Other than the appealing symmetry of being able to use a language to parse that same language, this feels very similar to https://stackoverflow.com/questions/1732348/regex-match-open...
Edit: I just checked and sadly someone beat me to it in 2019: https://news.ycombinator.com/item?id=20910120
Re: Is there a regular expression to detect a valid regular expression? (2008)
#4Damian Conway's https://metacpan.org/pod/PPR module defines a regex (in the commonly used sense) that can match perl source code - including perl regexes!
Edit: "The PPR module provides a single regular expression that defines a set of independent subpatterns suitable for matching entire Perl documents, as well as a wide range of individual syntactic components of Perl (i.e. statements, expressions, control blocks, variables, etc.)"
Re: Is there a regular expression to detect a valid regular expression? (2008)
#5I answered a funny regex question once, “can strings that are base64 encoded twice be matched with a regex?”
https://stackoverflow.com/questions/49650847/determine-if-st...
The answer is yes, they’re regular. :-D
Re: Is there a regular expression to detect a valid regular expression? (2008)
#6The user ID that asked the question looks to have last answered a question in 2016.
I'm not sure what this means. Have we asked and answered all the good questions already?
Re: Is there a regular expression to detect a valid regular expression? (2008)
#7Technically, the set of strings containing balanced parentheses is not a regular language...
Re: Is there a regular expression to detect a valid regular expression? (2008)
#8Oh man you've already got two problems? Maybe it's four now.
Re: Is there a regular expression to detect a valid regular expression? (2008)
#9I answered a funny regex question once, “can strings that are base64 encoded twice be matched with a regex?” https://stackoverflow.com/questions/49650847/determine-if-st... The answer is yes, they’re regular. :-D
That's amazing. Thank you!
Re: Is there a regular expression to detect a valid regular expression? (2008)
#10What about a regular expression that detects regular expressions that detect valid regular expressions?