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

comment on

( [id://3333]=superdoc: print w/replies, xml ) Need Help??

Good $localtime fellow monks

I have a large piece of code, and while debugging, the output routine is giving me the above message, lots. I am passing it an array of hasrefs (alerts basicaly), and trying to sort by the msg value in the hashrefs. I have distilled the problem to a one-liner. TBH, I expected the problem to drop out elsewhere in my code, surprised I see it in this:

perl -wle '@r=({k=>"r"},{k=>"s"},{k=>"t"});print $_->{k} for sort { $_ +->{k} cmp $_->{k} } @r' Use of uninitialized value in string comparison (cmp) at -e line 1. Use of uninitialized value in string comparison (cmp) at -e line 1. Use of uninitialized value in string comparison (cmp) at -e line 1. Use of uninitialized value in string comparison (cmp) at -e line 1. Use of uninitialized value in string comparison (cmp) at -e line 1. Use of uninitialized value in string comparison (cmp) at -e line 1. r s t

I get the same result if I deref it this way to:

perl -wle '@r=({k=>"r"},{k=>"s"},{k=>"t"});print $_->{k} for sort { $$_{k} cmp $$_{k} } @r'

Why does this happen, where is it finding unitialised values? and of course, how can I fix it?

Cheers,
R.

Pereant, qui ante nos nostra dixerunt!

In reply to Use of uninitialized value in string comparison (cmp) by Random_Walk

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 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?Last hourOther CB clients
Other Users?
Others drinking their drinks and smoking their pipes about the Monastery: (5)
As of 2024-03-29 06:42 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found