Beefy Boxes and Bandwidth Generously Provided by pair Networks BBQ
Perl: the Markov chain saw
 
PerlMonks  

Re: RFC: Perl regex to validate arithmetic expressions

by mellon85 (Monk)
on Feb 21, 2011 at 18:53 UTC ( #889463=note: print w/ replies, xml ) Need Help??


in reply to RFC: Perl regex to validate arithmetic expressions

You actually can parse an arithmetic expression with a "regular" expression if it uses a stack automata. Just think that a regular language can't even check if there is a correct number of parenthesis if the maximum depth is undefined, as such, strictly speaking that is not so much regular...


Comment on Re: RFC: Perl regex to validate arithmetic expressions
Re^2: RFC: Perl regex to validate arithmetic expressions
by JavaFan (Canon) on Feb 22, 2011 at 09:58 UTC
    Since 5.10, Perl regular expressions can match anything that's matched by a context-free grammar - and then some (backreferences add even more power). Matching balanced parenthesis is easy in 5.10 and later: /^(\((?1)*\))$/.

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://889463]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others pondering the Monastery: (9)
As of 2014-04-16 05:54 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    April first is:







    Results (414 votes), past polls