Hi all in the monastry -- hope you are not all sworn to silence during the festive season.

I have a small challenge, being fairly new to perl. I wish to step through a hash with

  while ( ($key, $value) = each %hash ){
  }

[download]

but then modify the hash by deleting key,value pairs from the hash after some processing if they meet a certain condition, with the while loop in progress.

I have this nagging worry that modifiying the contents of the hash on the fly will stuff up the orderly progression of the while loop and that some records may be missed.

Can anyone with a deeper knowledge of perl advise on this?

A workaround would be to establish a companion array

  @array = keys %hash;
  foreach $key (@array){
   # Access the hash, and do the deed including any hash
   # key, value deletions.
  }

[download]

but this doubles the memory requirements, and my files are huge. I would like to avoid this if it is not necessary.

Looking forward to hearing from you. My first post.

In reply to Stepping through a hash while modifiying its content by Gorgarian

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


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.