Re: $array[ 'Infinity' ]

No, this is not caused by numerical equivalence to zero. Nor is it caused by Infinity/inf differences:

@a = (5 .. 10);
print
$a['inf'], "\n",
$a[-inf], "\n",
-inf==0 ? "-inf is zero\n" : "-inf isn't zero\n",
'inf'==0 ? "inf is zero\n" : "inf isn't zero\n";

# still outputs 10 and 5 and states that the infinities aren't zeroes
[download]

perl --version says "This is perl, v5.8.8 built for x86_64-linux-thread-multi"

Update: The weird thing is that indexing by -inf gives the first element and indexing by inf gives the last one. That's not what I'd expect.

use strict; use warnings; print "Just Another Perl Hacker\n";

Comment on Re: $array[ 'Infinity' ] Download Code

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Re^2: $array[ 'Infinity' ] by quester (Vicar) on Dec 17, 2007 at 00:25 UTC
Using perl -MO=Deparse may shed some light on some of this weirdness, although I have no idea why on Earth anyone would implement 'inf' the way it works on my box. `perl -MO=Deparse -e 'print $n[inf]'` [download] prints `print $n[999];` [download] as does `perl -MO=Deparse -e 'print $n["inf"]'` [download] On the other hand, `perl -MO=Deparse -e 'print $n[-inf]'` [download] prints `print $n[-'inf'];` [download] `perl -MO=Deparse -e 'print "", inf==0 ? "a" : "b", 'inf'==0 ? "c" : "d +", -inf==0 ? "e" : "f"'` [download] prints `print '', 'inf' == 0 ? 'a' : 'b', 'inf' == 0 ? 'c' : 'd', -'inf' == 0 +? 'e' : 'f';` [download] As nearly as I can tell at the moment, inf is only equivalent 999 if it is used by itself as a subscript; it is taken as a bareword in a simple assignment, so `perl -MO=Deparse -e '$n[inf], $n[1+inf], $n[-inf] = inf'` [download] prints `$n[999], $n[1 + 'inf'], $n[-'inf'] = 'inf';` [download] My perl -v shows, `This is perl, v5.8.8 built for i486-linux-gnu-thread-multi` [download] Does anyone know why? - quester	[reply] [d/l] [select]
Re^3: $array[ 'Infinity' ] by educated_foo (Vicar) on Dec 17, 2007 at 01:36 UTC
That is terrifyingly weird. But the `999` is just an artifact of B::Deparse, as can be seen here. I'm not sure why it does that. Then again, it makes a kind of twisted sense that `$a[inf]` means "last element of @a", and (completely by accident) `$a[-inf]` means "last element counting from the end."	[reply] [d/l] [select]
Re^3: $array[ 'Infinity' ] by ww (Archbishop) on Dec 17, 2007 at 02:01 UTC
Oddly (or maybe not so oddly) I get different output on a w2k box from the first cited by quester: `perl -MO=Deparse -e "print $n[inf]" print $n[0]; -e syntax OK` [download] from... `perl -v This is perl, v5.8.8 built for MSWin32-x86-multi-thread (with 33 registered patches, see perl -V for more detail) ... Binary build 819 [267479] provided by ActiveState http://www.ActiveSta +te.com Built Aug 29 2006 12:42:41` [download]	[reply] [d/l] [select]
Re^4: $array[ 'Infinity' ] by ikegami (Patriarch) on Dec 20, 2007 at 00:25 UTC
It's been established that ActiveState's build doesn't support infinity.	[reply]
Re: $array[ 'Infinity' ] by benizi (Hermit) on Dec 19, 2007 at 23:55 UTC
As to the "why", X = 999 == 9(99) = 9*387420489. Nine to that power is a number aproximately 1.2 billion bits long. (log(9)/log(2) (9*9)). So, for all intents and purposes, it's infinity. ~~Since it's odd,~~ -X will be negative infinity So, it avoids the (possible?) non-portability of a raw 'inf' or '-inf'. Update:* Duh, Ben. Re: strikeout. Plus it's specifically negated. I was thinking (-9)99)	[reply]
Re^2: $array[ 'Infinity' ] by almut (Canon) on Dec 16, 2007 at 23:52 UTC
Interesting. I can confirm your results for "v5.8.8 built for x86_64-linux-thread-multi". For "v5.8.8 built for i486-linux-gnu-thread-multi", however, I'm just getting `10` for `'Infinity'` (or `inf`) and nothing (undef) for `-Infinity` (or `-inf`).	[reply] [d/l] [select]

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