Weirdness
Given Perl v5.8.0, stable version at Sep 19 2002 00:33:39, the following
are all valid Perl expressions:
3 * 9
3 ** 9
3 * * 9
3 * * * * 9
3 ** * 9
3 ** * * 9
3 ** * * * 9
3 ** * * * * 9
3 * * *
The following is not:
3 * * * 9
Of course this is a very ed up thing to try, don't ask me why I did.
But can anyone explain?
S.
--
Shevek
I am the Borg.
sub AUTOLOAD{my$i=$AUTOLOAD;my$x=shift;$i=~s/^.*://;print$x\n;eval
qq{*$AUTOLOAD=sub{my\$x=shift;return unless \$x%$i;{$x}(\$x);};};}
foreach my $i (3..65535) { {'2'}($i); }
Re: Weirdness
On Sun, Nov 03, 2002 at 11:14:44AM +, Shevek wrote:
Given Perl v5.8.0, stable version at Sep 19 2002 00:33:39, the following
are all valid Perl expressions:
3 * 9
3 ** 9
3 * * 9
3 * * * * 9
3 ** * 9
3 ** * * 9
3 ** * * * 9
3 ** * * * * 9
3 * * *
The following is not:
3 * * * 9
Of course this is a very ed up thing to try, don't ask me why I did.
But can anyone explain?
Given this:
perl -le 'print * * '
*main::*
and my limited knowledge of how tokenisers work
when expecting a term, ** or * * will be interpreted as a typeglob of * in main
when expecting an expression, ** will be interpreted as exponentiation
when expecting an expression, * will be interpreted as multiply
and it seems that:
perl -le 'print * 9 '
*main::9
*main::* and *main::9 aren't numeric, so they are treated as 0.
so you had
3 times 9
3 to the power of 9
3 times *main::9
3 times *main::* times 9
3 to the power of *main::9
then '3 ** * * 9' isn't valid, so you must have typed that somewhere.
3 to the power of *main::* times 9
3 to the power of *main::* times *main::9
3 times *main::*
none of the above was checked with Deparse. Here's the last one, as seen by
Deparse:
perl5.8.0 -MO=Deparse -le 'print 3 ** * * * * 9'
BEGIN { $/ = \n; $\ = \n; }
print 3 ** ** * *9;
-e syntax OK
And the reason I know all this - blame Abigail.
(a sig with ** something which has the value 1. ie 0 ** 0, which perl is
treating as 1. I don't know enough serious maths to know if 0 ** 0 is well
defined. See perl6-language for more maths)
Nicholas Clark
--
Brainfuck better than perl? http://www.perl.org/advocacy/spoofathon/
Re: Weirdness
On Sun, Nov 03, 2002 at 11:34:53AM +, Nicholas Clark wrote: [ question and explanation elided ] And the reason I know all this - blame Abigail. (a sig with ** something which has the value 1. ie 0 ** 0, which perl is treating as 1. I don't know enough serious maths to know if 0 ** 0 is well defined. See perl6-language for more maths) 0 ** x and x ** 0 have different limits as x approaches 0, so if I recall correctly , 0 ** 0 is an indeterminate form, but it is generally accepted (I think) that 1 is the most useful answer because that makes little things like the binomial theorem work properly. Disclaimer - it's many years since I did any real maths. [ Now waiting for someone to say it shows, and give a real answer. ] -- Paul Johnson - [EMAIL PROTECTED] http://www.pjcj.net
Re: webmail
On Wed, Oct 30, 2002 at 07:49:03PM -0800, Randal L. Schwartz wrote: Paul == Paul Makepeace [EMAIL PROTECTED] writes: Paul I am also amused and puzzled at the people writing huge tracts on why Paul PHP is crap while not at the same time acknowledging there are vastly Paul more websites written in PHP doing useful things for lots of people than Paul there are in perl -- witness the scrabbling to find even remotely Paul interesting success story cases for Perl (what recent ones have there Paul been?). A lot of the ones at http://perl.apache.org/outstanding/success_stories/ seem recent. And I suppose you haven't heard of match.com or citysearch.com or ticketmaster.com before? Oh wait, you're a brit. :) That's good to see -- match.com is certainly a massive site. Still, it seems a tiny number to me considering what's out there. Paul I suspect more revenue is generated from PHP sites than Perl Paul sites. I don't. I suspect PHP runs more hobby sites. I suspect Perl does more of the e-commerce heavy lifting and pretty-lifting. I dunno, in light of reports like the one on LWN I'm struggling to see this. PHP Overtakes Microsoft's ASP as Web's #1 Server-side Scripting Language: http://lwn.net/Articles/1433/ According to a Netcraft survey published in April 2002, PHP is now being used by over 24% of the sites on the Internet. Of the 37.6 million web sites reported worldwide (http://www.netcraft.com/Survey/index-200204.html), PHP is running on over 9 million sites and continues to grow at an explosive rate. Over the past two years PHP has averaged a 6.5% monthly growth rate. That's an enormous number of hobby sites :-) Oh well, who knows - my basic point is that for all the interesting discussion about how bad PHP is there's an awful lot of productive work going on with it, that same work that probably wouldn't've happened with perl. (I know at least half a dozen PHPers who were too scared by perl.) Paul -- Paul Makepeace ... http://paulm.com/ If I could write Java Code, then some masks would be smarter than others. -- http://paulm.com/toys/surrealism/
Re: webmail
On Mon, Nov 04, 2002 at 12:44:00AM +, Paul Makepeace wrote: According to a Netcraft survey published in April 2002, PHP is now being used by over 24% of the sites on the Internet. Of the 37.6 million web sites reported worldwide (http://www.netcraft.com/Survey/index-200204.html), PHP is running on over 9 million sites and continues to grow at an explosive rate. Over the past two years PHP has averaged a 6.5% monthly growth rate. That's an enormous number of hobby sites :-) Oh well, who knows - my basic point is that for all the interesting discussion about how bad PHP is there's an awful lot of productive work going on with it, that same work that probably wouldn't've happened with perl. (I know at least half a dozen PHPers who were too scared by perl.) I think the bad publicity that PHP gets is largely due to two/three things: a) The speed at which it evolves: PHP has went through a crazy development cycle in the last year or two.. quite a bit of the API changed to be more uniform, and other such language enhancements. This period is not over, Zend2 is on the way which will change some of the language syntax, although on saying that, perl6 is on the way too, and perl's syntax will probably change more than PHP's will with this upgrade. b) The number of bad PHP programmers: PHP is probably one of the easiest web languages in the world to pick up. Given that, and the number of .* in 24 hours books available for it, the universe now has a surplus of PHP coders who don't really know what they are doing. As a result of this, we now have a steady stream of security vulnerabilities published on major security mailling lists daily about insecure PHP packages (I think this is how the discussion started?). The actual PHP codebase itself has only had a few insecurities -- I haven't looked at the figures, but at a guess I'd say less than the likes of suidperl (which has been around for quite a long time I must admit, but I'm trying to make PHP look good here). A properly coded PHP project should be just as secure as it's perl or C (or insert-language-here) counterparts. It is the In-24-hrs-Newbie who is writing code like 'system(getenv(USERNAME));'. This could just as easily be done in any other language. (please skip the perl tainting rants :). c) Lack of traditions regarding project management and syntax style: Well organized PHP projects are few and far between; I've heard hundreds of anti-PHP arguments, most of them valid, but a large number have been that PHP does not cope well when given a large codebase (1000+ lines). If your PHP codebase has got messy, that is your fault, not the languages. PHP doesn't have a recognized way of organizing code (like Perl or Python modules), it leaves it up to you to be creative in finding a way. As a side note, there is a CPAN clone well under way, however, PEAR. The only real complaint I have with PHP is the memory management, which I have seen get messy in really simple situations. Apart from that, it's a nice neat little language. If you keep up with the development of the language (like any good programmer should anyway), you're sorted. Admittedly, PHP language development moves about 100 times faster then any other language at times, but thats just it's nature. /rant Dave.
Re: webmail
On 04/11/02 00:44 +, Paul Makepeace wrote: I dunno, in light of reports like the one on LWN I'm struggling to see this. PHP Overtakes Microsoft's ASP as Web's #1 Server-side Scripting Language: http://lwn.net/Articles/1433/ According to a Netcraft survey published in April 2002, PHP is now being used by over 24% of the sites on the Internet. Of the 37.6 million web sites reported worldwide (http://www.netcraft.com/Survey/index-200204.html), PHP is running on over 9 million sites and continues to grow at an explosive rate. Over the past two years PHP has averaged a 6.5% monthly growth rate. That's an enormous number of hobby sites :-) Current or ex-Netcrafters can correct me if I'm wrong, but the netcraft survey basically asks the http server what it's actually running, and so these figures are, pretty much, simply taken from distinct domains with an apache reporting that it has mod_php loaded. There are 2 major points with this: 1) Whilst mod_perl shows up in the same way, there's no direct way of Netcraft collecting data on vanilla apache servers which are being used with perl scripts (CGI.pm-enabled or otherwise). 2) Many servers, especially those at bulk hosting companies running virtual hosts for people, will be compiled with mod_php by default. Whether it's actually used by any/all of the sites on the box is a different point. The statistics may not be that accurate, basically. Having said that, I don't doubt that PHP is popular, and that it's very useful for a lot of people in a lot of situations. Personally I haven't used it very much (my old not-quite-dormant company has a couple of sites running geeklog, but that's pretty much someone else's responsibility), and I like the flexibility and power that I have with perl, especially combined with DBI and TT. Each to their own, horses for courses, and a bunch of other cliches...
