Array slice indexing bug (when mixing positive and negative notation) #5559

p5pRT · 2002-06-11T07:38:56Z

Migrated from rt.perl.org#9533 (status was 'resolved')

Searchable as RT9533$

p5pRT · 2002-06-11T07:38:56Z

From [email protected]

This is a bug report for perl from torbenh@mips.com,
generated with the help of perlbug 1.33 running under perl v5.6.1.

#!/usr/local/bin/perl -w

# I hope the bug is obvious: I expect all the 4 last cases to be the same
# I am using perl 5.6.1 on Sun/Solaris 5.8 - I also tried perl 5.6.0 on
# i386/Linux with same result
#
# /Torben Vendt Hansen

@a = qw(1 2 3 4 5);

print("\@a: @a\n");
print("OK: \$a[3] $a[3]\n");
print("OK: \$a[-2] $a[-2]\n");
print("OK: \@a[3 .. 4] @a[3 .. 4]\n");
print("OK: \@a[-2 .. -1] @a[-2 .. -1]\n");
print("BUG: \@a[3 .. -1] @a[3 .. -1]\n");
print("BUG: \@a[-2 .. 4] @a[-2 .. 4]\n");

Flags:
category=core
severity=high

Site configuration information for perl v5.6.1:

Configured by steve at Wed Apr 25 02:36:44 EDT 2001.

Summary of my perl5 (revision 5.0 version 6 subversion 1) configuration:
Platform:
osname=solaris, osvers=2.8, archname=sun4-solaris
uname='sunos solaris 5.8 generic sun4u sparc sunw,ultra-5_10 '
config_args='-Dcc=gcc -de'
hint=recommended, useposix=true, d_sigaction=define
usethreads=undef use5005threads=undef useithreads=undef usemultiplicity=undef
useperlio=undef d_sfio=undef uselargefiles=define usesocks=undef
use64bitint=undef use64bitall=undef uselongdouble=undef
Compiler:
cc='gcc', ccflags ='-fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
optimize='-O',
cppflags='-fno-strict-aliasing -I/usr/local/include'
ccversion='', gccversion='2.95.3 20010315 (release)', gccosandvers='solaris2.8'
intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=4321
d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
alignbytes=8, usemymalloc=y, prototype=define
Linker and Libraries:
ld='gcc', ldflags =' -L/usr/local/lib '
libpth=/usr/local/lib /usr/lib /usr/ccs/lib
libs=-lsocket -lnsl -lgdbm -ldb -ldl -lm -lc
perllibs=-lsocket -lnsl -ldl -lm -lc
libc=/lib/libc.so, so=so, useshrplib=false, libperl=libperl.a
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags=' '
cccdlflags='-fPIC', lddlflags='-G -L/usr/local/lib'

Locally applied patches:

@INC for perl v5.6.1:
/usr/local/lib/perl5/5.6.1/sun4-solaris
/usr/local/lib/perl5/5.6.1
/usr/local/lib/perl5/site_perl/5.6.1/sun4-solaris
/usr/local/lib/perl5/site_perl/5.6.1
/usr/local/lib/perl5/site_perl
.

Environment for perl v5.6.1:
HOME=/home/torbenh
LANG=C
LANGUAGE (unset)
LD_LIBRARY_PATH=/mips/sw/lsf42/sparcOS5_64/lib:/mips/sw/lsf42/sparcOS5_64/lib:/usr/local/lib:/usr/openwin/lib:/usr/dt/lib::/usr/local/freetds/lib
LOGDIR (unset)
PATH=/usr/local/lsf/sparcOS5_64/bin:.:/home/torbenh/bin:/home/torbenh/bin/Solaris:/usr/local/bin:/bin:/usr/bin:/sbin:/usr/sbin:/usr/ucb:/usr/ccs/bin:/usr/openwin/bin:/usr/dt/bin:/home/eng/bin
PERL_BADLANG (unset)
SHELL=/usr/local/bin/tcsh

p5pRT · 2002-06-11T07:43:14Z

From [Unknown Contact. See original ticket]

On Jun 11, Torben Vendt Hansen said:

# I hope the bug is obvious: I expect all the 4 last cases to be the same
# I am using perl 5.6.1 on Sun/Solaris 5.8 - I also tried perl 5.6.0 on
# i386/Linux with same result

It is not a bug.

@a = qw(1 2 3 4 5);

print("BUG: \@a[3 .. -1] @a[3 .. -1]\n");
print("BUG: \@a[-2 .. 4] @a[-2 .. 4]\n");

@a[-2 .. 4] is merely shorthand for @a[-2, -1, 0, 1, 2, 3, 4], which is
consistant and proper. @a[3 .. -1] should yield a warning; the range
operator takes two operands, a low and a high, in that order. It is NOT
magically linked to arrays somehow, and it does not work backwards.

--
Jeff "japhy" Pinyan japhy@pobox.com http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
** Look for "Regular Expressions in Perl" published by Manning, in 2002 **
<stu> what does y/// stand for? <tenderpuss> why, yansliterate of course.
[ I'm looking for programming work. If you like my work, let me know. ]

p5pRT · 2002-06-11T12:44:35Z

From @schwern

On Tue, Jun 11, 2002 at 10:41:58AM -0400, Jeff 'japhy' Pinyan wrote:

@a[-2 .. 4] is merely shorthand for @a[-2, -1, 0, 1, 2, 3, 4], which is
consistant and proper. @a[3 .. -1] should yield a warning; the range
operator takes two operands, a low and a high, in that order. It is NOT
magically linked to arrays somehow, and it does not work backwards.

Maybe the bug is that it doesn't produce a warning when used backwards.

$ perl -wle '@a = qw(1 2 3 4 5); print @a[3 .. -1]'

Or maybe it should just work backwards. :)

--
This sig file temporarily out of order.

p5pRT · 2002-06-11T14:41:45Z

From [Unknown Contact. See original ticket]

-----BEGIN PGP SIGNED MESSAGE-----

Moin,

From: Michael G Schwern <schwern@pobox.com>
To: japhy@pobox.com
Cc: Torben Vendt Hansen <torbenh@mips.com>, perl5-porters@perl.org
Date: Tue, 11 Jun 2002 15:43:07 -0400
Message-id: <20020611194307.GM31617@ool-18b93024.dyn.optonline.net>

On Tue, Jun 11, 2002 at 10:41:58AM -0400, Jeff 'japhy' Pinyan wrote:

@a[-2 .. 4] is merely shorthand for @a[-2, -1, 0, 1, 2, 3, 4], which is
consistant and proper. @a[3 .. -1] should yield a warning; the range
operator takes two operands, a low and a high, in that order. It is NOT
magically linked to arrays somehow, and it does not work backwards.

Maybe the bug is that it doesn't produce a warning when used backwards.

$ perl -wle '@a = qw(1 2 3 4 5); print @a[3 .. -1]'

Or maybe it should just work backwards. :)

You could overload it. Oh wait, I never managed to bribe^Wlobby someone to
implement this...:)

- --
perl -MDev::Bollocks -e'print Dev::Bollocks->rand(),"\n"'
ambassadorially transform visionary m-commerce

http://bloodgate.com/perl My current Perl projects
PGP key available on http://bloodgate.com/tels.asc or via email

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.6 (GNU/Linux)
Comment: When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

iQEVAwUBPQZvGXcLPEOTuEwVAQHNsQf+Ml4PTgnv4B2OhAFsyJBmg4k1GtCQN4/1
vVzEGTdMcN8koijMFFWlNJ6lf85JFMQDh0UJnhoCloplgciWSgqGr6nJXAZT/q7p
v1C5GB6J+75xZLKfFLJfMvB32Ec0kIZp92X391byGh/q7GgJaAtjJMQs6clvUbe3
Tp22x6czvrI3n4+2ZizYwkFkAQqpIzhd7+Qnx9uS1sNkjoyt28Ag0STlnxRdWJry
/whmxGKzRlpxWlj9E+ROSgCkstfdq4ndAtc8VFMYn/q8rs2CEQ8kMsCeIc7L8QSn
XSoNf4BiqtJE2yrQYGVNc85/kQwaH9zm6vG6QJrx8y6HKJMkVWFeZw==
=N4yf
-----END PGP SIGNATURE-----

p5pRT · 2002-06-12T03:00:50Z

From @Abigail

On Tue, Jun 11, 2002 at 03:43:07PM -0400, Michael G Schwern wrote:

On Tue, Jun 11, 2002 at 10:41:58AM -0400, Jeff 'japhy' Pinyan wrote:

@a[-2 .. 4] is merely shorthand for @a[-2, -1, 0, 1, 2, 3, 4], which is
consistant and proper. @a[3 .. -1] should yield a warning; the range
operator takes two operands, a low and a high, in that order. It is NOT
magically linked to arrays somehow, and it does not work backwards.

Maybe the bug is that it doesn't produce a warning when used backwards.

I don't think so. I find the behaviour useful and I often exploit it.
Not with 2 constants in the range of course, but with one of them
variable.

# Deal with the rest of the array.
foreach my $elem (@array [$i .. $#array]) { ... }

And this neatly skips doesn't run the loop if the range is empty,
that is, if $i > $#array.

$ perl -wle '@a = qw(1 2 3 4 5); print @a[3 .. -1]'

Or maybe it should just work backwards. :)

That's why we have $#array and @array in scalar context.

Abigail

p5pRT · 2002-06-12T03:15:12Z

From @iabyn

On Wed, Jun 12, 2002 at 02:59:10AM -0700, Abigail wrote:

On Tue, Jun 11, 2002 at 03:43:07PM -0400, Michael G Schwern wrote:

On Tue, Jun 11, 2002 at 10:41:58AM -0400, Jeff 'japhy' Pinyan wrote:

@a[-2 .. 4] is merely shorthand for @a[-2, -1, 0, 1, 2, 3, 4], which is
consistant and proper. @a[3 .. -1] should yield a warning; the range
operator takes two operands, a low and a high, in that order. It is NOT
magically linked to arrays somehow, and it does not work backwards.

Maybe the bug is that it doesn't produce a warning when used backwards.

I don't think so. I find the behaviour useful and I often exploit it.
Not with 2 constants in the range of course, but with one of them
variable.
\# Deal with the rest of the array\.
foreach my $elem $@&#8203;array \[$i \.\. $\#array\]$ \{  \.\.\.  \}

Maybe a warning only when both values are constant?
(Of course, this would still annoy those people using eval.)

Dave.

--
"Emacs isn't a bad OS once you get used to it.
It just lacks a decent editor."

p5pRT closed this as completed Nov 28, 2003

p5pRT added Severity High distro-Solaris type-core labels Oct 18, 2019

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Array slice indexing bug (when mixing positive and negative notation) #5559

Array slice indexing bug (when mixing positive and negative notation) #5559

p5pRT commented Jun 11, 2002

p5pRT commented Jun 11, 2002

p5pRT commented Jun 11, 2002

p5pRT commented Jun 11, 2002

p5pRT commented Jun 11, 2002

p5pRT commented Jun 12, 2002

p5pRT commented Jun 12, 2002

Array slice indexing bug (when mixing positive and negative notation) #5559

Array slice indexing bug (when mixing positive and negative notation) #5559

Comments

p5pRT commented Jun 11, 2002

p5pRT commented Jun 11, 2002

From [email protected]

p5pRT commented Jun 11, 2002

From [Unknown Contact. See original ticket]

p5pRT commented Jun 11, 2002

From @schwern

p5pRT commented Jun 11, 2002

From [Unknown Contact. See original ticket]

p5pRT commented Jun 12, 2002

From @Abigail

p5pRT commented Jun 12, 2002

From @iabyn