Update: As Not_a_Number points out below, the behavior described in this post applies not only to 1 (as I originally stated), but to 0 as well. And, after reading merlyn's post, well, it looks like there's a huge number of constants—all those strings beginning with "di", "ds", or "ig"—that perl won't warn about when they are evaluated in a void context. See the code responsible for this behavior, kindly posted by AM.
OK, here's another idle Perl arcana question. A scalar constant in a void context will result in a warning, unless this constant evaluates to a numeric value of 1; e.g.:
% perl -wce 5
Useless use of a constant in void context at -e line 1.
-e syntax OK
% perl -wce 1
-e syntax OK
% perl -wce '5**0'
-e syntax OK
% perl -wce 1.00
-e syntax OK
% perl -wce 'q(1)'
Useless use of a constant in void context at -e line 1.
-e syntax OK
Does anyone know the rationale for this special dispensation for (numeric) 1? The only one I can think of (and it's a pretty tortured one) is that it silences the warning that would have otherwise been triggered by the usual require-appeasing "1;" when one checks a module's syntax using perl -wc.
Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
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, 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, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
Outside of code tags, you may need to use entities for some characters:
| |
For: |
|
Use: |
| & | | & |
| < | | < |
| > | | > |
| [ | | [ |
| ] | | ] |
Link using PerlMonks shortcuts! What shortcuts can I use for linking?
See Writeup Formatting Tips and other pages linked from there for more info.
|
|
