Re^3: $array[ 'Infinity' ]

in reply to Re^2: $array[ 'Infinity' ]
in thread $array[ 'Infinity' ]

Is Perl suppose to support Infinity as a number? If so, it has two bugs: it doesn't work, and it's not in the docs. It's not in the 5.10.0 docs either.

It's not recognized by the parser:

>perl -e "use Devel::Peek; $x="Infinity"; Dump($x); $x=Infinity; Dump(
+$x)"
SV = PV(0x22612c) at 0x226000
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x182cb54 "Infinity"\0
  CUR = 8
  LEN = 12
SV = PV(0x22612c) at 0x226000
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x182cb54 "Infinity"\0
  CUR = 8
  LEN = 12

>perl -e "use Devel::Peek; $x="-Infinity"; Dump($x); $x=-Infinity; Dum
+p($x)"
SV = PV(0x226150) at 0x226000
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x1835404 "-Infinity"\0
  CUR = 9
  LEN = 12
SV = PV(0x226150) at 0x226000
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x1835404 "-Infinity"\0
  CUR = 9
  LEN = 12
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I also get different output from the commands you issued.

>perl -le "print 0+(-Infinity)"
0

>perl -le "print 0+('Infinity')"
0
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>perl -v

This is perl, v5.8.8 built for MSWin32-x86-multi-thread
(with 25 registered patches, see perl -V for more detail)

Copyright 1987-2006, Larry Wall

Binary build 817 [257965] provided by ActiveState http://www.ActiveSta
+te.com
Built Mar 20 2006 17:54:25

...
[download]

Has this been discussed on P5P?

Comment on Re^3: $array[ 'Infinity' ] Select or Download Code

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Re^4: $array[ 'Infinity' ] by ysth (Canon) on Dec 17, 2007 at 01:38 UTC
It's only supported where the underlying libc supports it (in particular, strtod). And even that was broken from some point in the past through 5.8.7. -- CollegeGear.com - more than just college gear (though, yes, we have college-branded teddy bears)	[reply]
Re^4: $array[ 'Infinity' ] by blokhead (Monsignor) on Dec 16, 2007 at 23:45 UTC
I have no idea what it's supposed to do. I couldn't find anything in my local docs about it either (nor about NaN, which has similar behavior on my build). Maybe it depends on the local floating-point arithmetic library? Searching came up with: this perl5.porters msg, and also FMTYEWTK about is_numeric, which seems to suggest that perl calls to the atof() library function. Finally, bignum suggests that "Perl doesn't always handle bareword NaN/inf properly." blokhead	[reply]

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