Hi guys, I'm sure this question has come up before, but I can't make a decent search query that turns up anything useful. Why does it appear that 0 (zero, 0x00) has non-zero bits in it? This came up when I tracked down a bug that ultimately reduced to: 
% perl -le 'print vec(0x0, 5,1)'
1

[download]
Strange! But: 
% perl -le 'print vec(0x0, 6,1)'
0

[download]
Huh? And: 
% perl -le 'print vec("", 5,1)'
0

[download]
I thought "" would be the same as 0 in memory -- all 0 bits! So I naturally looked up the perldoc on vec(), and tried out this: 
% perl -le '@bits = split(//, unpack("b*", 0x0)); print "@bits"'
0 0 0 0 1 1 0 0

[download]
What gives? Can anyone explain to me why 0 has two non-zero bits in it? And is the only real solution to my bug to just use bit operations rather than vec() (ugh!) Thanks!

In reply to bits, vec(), zero, and unpack weirdness by Anonymous Monk

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.