News for hackers. Stuff that matters.

A comment on Is there a regular expression to detect a valid regular expression?. Parent comment

Re:Is there a regular expression to detect a valid regular e... by tgv on Sunday September 08, 2019 @11:19AM (#20911045)
It depends on the representation. If the representation is in the FSA format (state, character, state), it becomes nearly trivial.
[ Parent | on HN ]
Re:Is there a regular expression to detect a valid regular e... by ggrrhh_ta on Sunday September 08, 2019 @11:55AM (#20911276)
Very underrated comment. Very good point to give food for thought although I think it is clear that it was meant to be on the usual textual representation using the simplest re language (without extensions).
[ Parent | on HN ]
Re:Is there a regular expression to detect a valid regular e... by morelisp on Sunday September 08, 2019 @12:08PM (#20911359)
An analogous problem for this representation would be detecting transitions to undefined states, or ambiguous (duplicate) transitions.
[ Parent | on HN ]
Re:Is there a regular expression to detect a valid regular e... by tgv on Monday September 09, 2019 @03:17AM (#20915907)
I didn't verify it, but my intuition says that can't be done with a CFG; it seems at least context-sensitive.
[ Parent | on HN ]