Is there a regular expression to detect a valid regular expression?
https://stackoverflow.com/questions/172303/is-there-a-regular-expression-to-detect-a-valid-regular-expression
(submitted by lelf)
programming theory talk
@hntooter the accepted answer is misleading if you're not paying attention.
A regular expression cannot detect a valid regular expression.
An Extended regular expression (like the ones most people use nowadays) can detect a non-extended regular expression.
The third answer is the correct one: https://stackoverflow.com/a/172363
re: programming theory talk
@lizardsquid @hntooter Note that stackoverflow shows non-accepted answers in random order, possibly with biasing based on either votes or time, depending on what sorting mode you have it in. You can't guarantee that this will be the third answer every time you load the page (it was the fifth when I clicked the link, for instance)
re: programming theory talk
@lizardsquid @hntooter it'd be less atrocious if it was obvious that there were sorting options
I think it defaults to sort by votes though
the randomness is supposed to make sure that new answers don't get lost under old ones just because the old ones have had more time to accumulate votes, I think