Beefy Boxes and Bandwidth Generously Provided by pair Networks
"be consistent"
 
PerlMonks  

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
BTW pos and regex m//g is very dangerous to use in a while loop if you do more regexes on the same string. For example the following code, similar to yours, loops once OK with the source string the same as yours. (The modification is search for a vowel. Search for the next 'x'. Search for next vowel if there is one)

However if we set $var = 'the quick brown fox jumped' then the same code gets into some endless loop whereas $var = 'The quick brown fox jump x' loops twice OK.

$var = 'the quick brown fox'; while( $var =~ m/([aeiou])/g ) { print "\n$var Matched '$1' \@ pos:", pos($var), "\n"; $var =~ m/x/g; print "$var : Matched X \@ pos:", pos($var), "\n"; }
I'm not quite sure whether this is defined behaviour but it caused me some head scratching when trying to parse some text into name/value bits. There are of course any number of work arounds, but its a bit of a surprise when misformed data causes your code to hang.

Dingus


Enter any 47-digit prime number to continue.

In reply to Re: pos()atively dangerous. by dingus
in thread pos()atively mysterious. by BrowserUk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others having an uproarious good time at the Monastery: (2)
As of 2022-05-20 13:55 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    Do you prefer to work remotely?



    Results (73 votes). Check out past polls.

    Notices?