-'-10' eq '+10' #8045

p5pRT · 2005-07-27T22:43:23Z

Migrated from rt.perl.org#36675 (status was 'resolved')

Searchable as RT36675$

p5pRT · 2005-07-27T22:43:24Z

From pfusik@op.pl

This is a bug report for perl from pfusik@op.pl,
generated with the help of perlbug 1.35 running under perl v5.8.7.

The behavior of the unary minus operator is inconsistent between
strings representing positive and negative numbers:

perl -le 'print for -"10",-"10.0",-"10foo",-"-10",-"-10.0",-"-10foo",-" -10",-" -10.0",-" -10foo"'
-10
-10
-10
+10
+10.0
+10foo
10
10
10

Perl guesses whether the argument of '-' is a number.
I think that all strings in the above example represent numbers.
Note that strings starting with a minus are not treated as numbers
-- I think they should be. However, with a leading space, they _are_
treated as numbers.

Flags:
category=core
severity=medium

Site configuration information for perl v5.8.7:

Configured by ActiveState at Sat Jun 4 07:30:27 PDT 2005.

Summary of my perl5 (revision 5 version 8 subversion 7) configuration:
Platform:
osname=linux, osvers=2.2.17, archname=i686-linux-thread-multi
uname='linux gimlet 2.2.17 #1 sun jun 25 09:24:41 est 2000 i686 unknown '

config_args='-ders -Dcc=gcc -Dusethreads -Duseithreads -Ud_sigsetjmp -Uinstallusrbinperl -Ulocincpth= -Uloclibpth= -Accflags=-DUSE_S
ITECUSTOMIZE -Duselargefiles -Accflags=-DNO_HASH_SEED -Uusemallocwrap -Dinc_version_list=5.8.6/$archname 5.8.6 5.8.4/$archname 5.8.4
5.8.3/$archname 5.8.3 5.8.2/$archname 5.8.2 5.8.1/$archname 5.8.1 5.8.0/$archname
5.8.0 -Duseshrplib -Dprefix=/opt/ActivePerl-5.8 -Accflags=-DBUILT_BY_ACTIVESTATE -Dcf_by=ActiveState -Dcf_email=support@ActiveState.
com'
hint=recommended, useposix=true, d_sigaction=define
usethreads=define use5005threads=undef useithreads=define usemultiplicity=define
useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
use64bitint=undef use64bitall=undef uselongdouble=undef
usemymalloc=n, bincompat5005=undef
Compiler:
cc='gcc', ccflags
='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DUSE_SITECUSTOMIZE -DNO_HASH_SEED -DBUILT_BY_ACTIVESTATE -fno-strict-aliasing -pip
e -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
optimize='-O2',

cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DUSE_SITECUSTOMIZE -DNO_HASH_SEED -DBUILT_BY_ACTIVESTATE -fno-strict-alias
ing -pipe'
ccversion='', gccversion='2.95.2 20000220 (Debian GNU/Linux)', gccosandvers=''
intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
alignbytes=4, prototype=define
Linker and Libraries:
ld='gcc', ldflags =''
libpth=/lib /usr/lib /usr/local/lib
libs=-lnsl -lndbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc -lposix
perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc -lposix
libc=/lib/libc-2.1.3.so, so=so, useshrplib=true, libperl=libperl.so
gnulibc_version='2.1.3'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef,
ccdlflags='-Wl,-E -Wl,-rpath,/opt/ActivePerl-5.8/lib/5.8.7/i686-linux-thread-multi/CORE'
cccdlflags='-fpic', lddlflags='-shared'

Locally applied patches:
ACTIVEPERL_LOCAL_PATCHES_ENTRY
# if !defined(PERL_DARWIN)
Iin_load_module moved for compatibility with build 806
# endif
# if defined(__hpux)
Avoid signal flag SA_RESTART for older versions of HP-UX
# endif
PerlEx hacks for CGI::Carp
Less verbose ExtUtils::Install and Pod::Find
instmodsh upgraded from ExtUtils-MakeMaker-6.25
24699 ICMP_UNREACHABLE handling in Net::Ping
21540 Fix backward-compatibility issues in if.pm

@INC for perl v5.8.7:
/opt/ActivePerl-5.8/lib/5.8.7/i686-linux-thread-multi
/opt/ActivePerl-5.8/lib/5.8.7
/opt/ActivePerl-5.8/lib/site_perl/5.8.7/i686-linux-thread-multi
/opt/ActivePerl-5.8/lib/site_perl/5.8.7
/opt/ActivePerl-5.8/lib/site_perl
.

Environment for perl v5.8.7:
HOME=/home/fox
LANG=en_US.UTF-8
LANGUAGE (unset)
LD_LIBRARY_PATH (unset)
LOGDIR (unset)
PATH=/opt/ActivePerl-5.8/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/usr/java/j2sdk1.4.2_01/bin:/home/fox/bin
PERL_BADLANG (unset)
SHELL=/bin/bash

p5pRT · 2005-12-16T17:54:05Z

From @smpeters

[pfusik@op.pl - Wed Jul 27 15:43:24 2005]:

This is a bug report for perl from pfusik@op.pl,
generated with the help of perlbug 1.35 running under perl v5.8.7.

-----------------------------------------------------------------

The behavior of the unary minus operator is inconsistent between
strings representing positive and negative numbers:

perl -le 'print for
-"10",-"10.0",-"10foo",-"-10",-"-10.0",-"-10foo",-" -10",-" -10.0",-"
-10foo"'
-10
-10
-10
+10
+10.0
+10foo
10
10
10

Perl guesses whether the argument of '-' is a number.
I think that all strings in the above example represent numbers.
Note that strings starting with a minus are not treated as numbers
-- I think they should be. However, with a leading space, they _are_
treated as numbers.

Let's see what Scalar::Util::looks_like_number() says...

steve@kirk:~/perl-current$ perl -MScalar::Util=looks_like_number -
le 'for(-"10" \
,-"10.0",-"10foo",-"-10",-"-10.0",-"-\ 10foo",-" -10",-" -10.0",-" -
10foo") \
{ print; print looks_like_number($_) ? "YES" : "NO"}'
-10
YES
-10
YES
-10
YES
+10
YES
+10.0
YES
+ 10foo
NO
10
YES
10
YES
10
YES

Note that strings starting with a minus are not treated as numbers

Perl certainly does treat them like numbers when they appear to be
numbers. In your particular example, however, Perl doesn't believe
that the string "-\ 10foo" is a number, and I really have to agree with
it.

p5pRT · 2005-12-16T17:54:06Z

The RT System itself - Status changed from 'new' to 'open'

p5pRT · 2005-12-16T17:54:06Z

@smpeters - Status changed from 'open' to 'resolved'

p5pRT · 2005-12-17T04:26:30Z

From BQW10602@nifty.com

The behavior of the unary minus operator is inconsistent between
strings representing positive and negative numbers:

perl -le 'print for
-"10",-"10.0",-"10foo",-"-10",-"-10.0",-"-10foo",-" -10",-" -10.0",-"
-10foo"'
-10
-10
-10
+10
+10.0
+10foo
10
10
10

Perl guesses whether the argument of '-' is a number.
I think that all strings in the above example represent numbers.
Note that strings starting with a minus are not treated as numbers
-- I think they should be. However, with a leading space, they _are_
treated as numbers.

It is documented in perlop.pod that unary minus opposes the sign
at the start of a string. (try not-a-number, like -"-xyz")

Unary ``-''
.... Otherwise, if the string starts with a plus or minus,
a string starting with the opposite sign is returned.

cf. PP(pp_negate)
...
else if (SvPOKp(sv)) {
...
else if (*s == '+' || *s == '-') {
sv_setsv(TARG, sv);
*SvPV_force(TARG, len) = *s == '-' ? '+' : '-';
}

I think the case of (-'-10' eq '+10') is conformable
with the documentation (thus not a bug).
(I guess the case of -" -10.0" is not (clearly?) documented.)

Regards,
SADAHIRO Tomoyuki

p5pRT · 2005-12-17T15:37:34Z

From @smpeters

[BQW10602@nifty.com - Fri Dec 16 20:26:30 2005]:

The behavior of the unary minus operator is inconsistent between
strings representing positive and negative numbers:

perl -le 'print for
-"10",-"10.0",-"10foo",-"-10",-"-10.0",-"-10foo",-" -10",-" -10.0",-"
-10foo"'
-10
-10
-10
+10
+10.0
+10foo
10
10
10

Perl guesses whether the argument of '-' is a number.
I think that all strings in the above example represent numbers.
Note that strings starting with a minus are not treated as numbers
-- I think they should be. However, with a leading space, they _are_
treated as numbers.

It is documented in perlop.pod that unary minus opposes the sign
at the start of a string. (try not-a-number, like -"-xyz")

Unary ``-''
.... Otherwise, if the string starts with a plus or minus,
a string starting with the opposite sign is returned.

cf. PP(pp_negate)
...
else if (SvPOKp(sv)) {
...
else if (*s == '+' || *s == '-') {
sv_setsv(TARG, sv);
*SvPV_force(TARG, len) = *s == '-' ? '+' : '-';
}

I think the case of (-'-10' eq '+10') is conformable
with the documentation (thus not a bug).
(I guess the case of -" -10.0" is not (clearly?) documented.)

No, its not. The following change fixes this. Also, much of the string
handling for arithmetic negation is under- or non-tested. The change
also adds t/op/negate.t to remedy this.

Change 26387 by stevep@stevep-mccoy on 2005/12/17 15:35:45

Addition documentation explaining aritmetic negation on strings. Also,
additional test cases based partially on code by Piotr Fusik in
RT #36675: -'-10' eq '+10'.

Affected files ...

... //depot/perl/pod/perlop.pod#136 edit
... //depot/perl/t/op/negate.t#1 add

Differences ...

==== //depot/perl/pod/perlop.pod#136 (text) ====

@@ -199,7 +199,11 @@
concatenated with the identifier is returned. Otherwise, if the string
starts with a plus or minus, a string starting with the opposite sign
is returned. One effect of these rules is that -bareword is equivalent
-to the string "-bareword".
+to the string "-bareword". If, however, the string begins with a
+non-alphabetic characters, Perl will attempt to convert the string to a
numeric
+and the arithmetic negation is performed. If the string cannot be cleanly
+converted to a numeric, Perl will give the warning B<Argument "the string"
+isn't numeric in negation (-) at ...>.
X<-> X<negation, arithmetic>

Unary "~" performs bitwise negation, i.e., 1's complement. For

p5pRT · 2005-12-17T15:42:47Z

From @smpeters

[stmpeters - Sat Dec 17 07:37:34 2005]:

[BQW10602@nifty.com - Fri Dec 16 20:26:30 2005]:

The behavior of the unary minus operator is inconsistent between
strings representing positive and negative numbers:

perl -le 'print for
-"10",-"10.0",-"10foo",-"-10",-"-10.0",-"-10foo",-" -10",-" -10.0",-"
-10foo"'
-10
-10
-10
+10
+10.0
+10foo
10
10
10

Perl guesses whether the argument of '-' is a number.
I think that all strings in the above example represent numbers.
Note that strings starting with a minus are not treated as numbers
-- I think they should be. However, with a leading space, they _are_
treated as numbers.

It is documented in perlop.pod that unary minus opposes the sign
at the start of a string. (try not-a-number, like -"-xyz")

Unary ``-''
.... Otherwise, if the string starts with a plus or minus,
a string starting with the opposite sign is returned.

cf. PP(pp_negate)
...
else if (SvPOKp(sv)) {
...
else if (*s == '+' || *s == '-') {
sv_setsv(TARG, sv);
*SvPV_force(TARG, len) = *s == '-' ? '+' : '-';
}

I think the case of (-'-10' eq '+10') is conformable
with the documentation (thus not a bug).
(I guess the case of -" -10.0" is not (clearly?) documented.)

No, its not. The following change fixes this. Also, much of the string
handling for arithmetic negation is under- or non-tested. The change
also adds t/op/negate.t to remedy this.

Change 26387 by stevep@stevep-mccoy on 2005/12/17 15:35:45
Addition documentation explaining aritmetic negation on strings\.  Also\,
additional test cases based partially on code by Piotr Fusik in 
RT \#36675&#8203;: \-'\-10' eq '\+10'\.
Affected files ...

... //depot/perl/pod/perlop.pod#136 edit
... //depot/perl/t/op/negate.t#1 add

Differences ...

==== //depot/perl/pod/perlop.pod#136 (text) ====

@@ -199,7 +199,11 @@
concatenated with the identifier is returned. Otherwise, if the string
starts with a plus or minus, a string starting with the opposite sign
is returned. One effect of these rules is that -bareword is equivalent
-to the string "-bareword".
+to the string "-bareword". If, however, the string begins with a
+non-alphabetic characters, Perl will attempt to convert the string to a
numeric
+and the arithmetic negation is performed. If the string cannot be
cleanly
+converted to a numeric, Perl will give the warning B<Argument "the
string"
+isn't numeric in negation (-) at ...>.
X<-> X<negation, arithmetic>

Unary "~" performs bitwise negation, i.e., 1's complement. For

Errr... a bit clearer is

Change 26388 by stevep@stevep-mccoy on 2005/12/17 15:41:38

Fix a typo and add some clarification to change #26387.

Affected files ...

... //depot/perl/pod/perlop.pod#137 edit

Differences ...

==== //depot/perl/pod/perlop.pod#137 (text) ====

@@ -200,10 +200,10 @@
starts with a plus or minus, a string starting with the opposite sign
is returned. One effect of these rules is that -bareword is equivalent
to the string "-bareword". If, however, the string begins with a
-non-alphabetic characters, Perl will attempt to convert the string to a
numeric
-and the arithmetic negation is performed. If the string cannot be cleanly
-converted to a numeric, Perl will give the warning B<Argument "the string"
-isn't numeric in negation (-) at ...>.
+non-alphabetic character (exluding "+" or "-"), Perl will attempt to
convert
+the string to a numeric and the arithmetic negation is performed. If the
+string cannot be cleanly converted to a numeric, Perl will give the warning
+B<Argument "the string" isn't numeric in negation (-) at ...>.
X<-> X<negation, arithmetic>

Unary "~" performs bitwise negation, i.e., 1's complement. For

p5pRT · 2005-12-17T16:07:53Z

From @tamias

On Sat, Dec 17, 2005 at 07:42:49AM -0800, Steve Peters via RT wrote:

==== //depot/perl/pod/perlop.pod#137 (text) ====

@@ -200,10 +200,10 @@
starts with a plus or minus, a string starting with the opposite sign
is returned. One effect of these rules is that -bareword is equivalent
to the string "-bareword". If, however, the string begins with a
-non-alphabetic characters, Perl will attempt to convert the string to a
numeric
-and the arithmetic negation is performed. If the string cannot be cleanly
-converted to a numeric, Perl will give the warning B<Argument "the string"
-isn't numeric in negation (-) at ...>.
+non-alphabetic character (exluding "+" or "-"), Perl will attempt to
convert
+the string to a numeric and the arithmetic negation is performed. If the
+string cannot be cleanly converted to a numeric, Perl will give the warning
+B<Argument "the string" isn't numeric in negation (-) at ...>.
X<-> X<negation, arithmetic>

Nits: "exluding" should be "excluding"; "numeric" is an adjective, not a
noun, so it should be replaced with "number".

Ronald

p5pRT closed this as completed Dec 16, 2005

p5pRT added the Severity Low label Oct 18, 2019

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-'-10' eq '+10' #8045

-'-10' eq '+10' #8045

p5pRT commented Jul 27, 2005

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-'-10' eq '+10' #8045

-'-10' eq '+10' #8045

Comments

p5pRT commented Jul 27, 2005

p5pRT commented Jul 27, 2005

From pfusik@op.pl

p5pRT commented Dec 16, 2005

From @smpeters

p5pRT commented Dec 16, 2005

p5pRT commented Dec 16, 2005

p5pRT commented Dec 17, 2005

From BQW10602@nifty.com

p5pRT commented Dec 17, 2005

From @smpeters

p5pRT commented Dec 17, 2005

From @smpeters

p5pRT commented Dec 17, 2005

From @tamias