Smart match doesn't work with list and given-when

[p5pRT]

Migrated from rt.perl.org#75152 (status was 'rejected')

Searchable as RT75152$

[p5pRT]

From [email protected]

Hello.

I tried to run the follow script, but I get wrong result.

I checked it, I think is correct.

Smarts matches in lines 12 and 16 doesn't work as expected. This piece of
code is part of a largest program, but this piece gives a wrong answer to me
(all numbers are odd!).

Hugs! Thanks by attention.

Case of test used​:

---

1 #!/usr/bin/perl
2
3 use 5.010;
4
5 print "Enter number​: ";
6 chomp($number = <STDIN>) while (!($number ~~ /^\s*(0|[1-9]+)\s*$/));
7
8 @​divisors = &getdivisors($number);
9
10 say "Divisors​: @​divisors";
11 given( $number ) {
12 when( @​divisors ~~ 2 ) {
13 say "$_ is a even number.";
14 continue;
15 }
16 when( !(@​divisors ~~ 2) ) {
17 say "$_ is a odd number.";
18 }
19 }
20
21 sub getdivisors {
22 my ($div, @​divisors) = (1);
23
24 while ($div <= $_[0]) {
25 push(@​divisors, $div) unless ($_[0] % $div);
26 ++$div;
27 }
28
29 return @​divisors;
30 }

---

Use of uninitialized value $category in concatenation (.) or string at
/usr/local/bin/perlbug line 645.
Use of uninitialized value $severity in concatenation (.) or string at
/usr/local/bin/perlbug line 645.

---

Flags​:
  category=?
  severity=high

---

Site configuration information for perl 5.12.0​:

Configured by eof at Tue May 11 08​:12​:38 BRT 2010.

Summary of my perl5 (revision 5 version 12 subversion 0) configuration​:

  Platform​:
  osname=linux, osvers=2.6.32-22-generic, archname=i686-linux
  uname='linux golden-eagle 2.6.32-22-generic #33-ubuntu smp wed apr 28
13​:27​:30 utc 2010 i686 gnulinux '
  config_args='-de'
  hint=recommended, useposix=true, d_sigaction=define
  useithreads=undef, usemultiplicity=undef
  useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
  use64bitint=undef, use64bitall=undef, uselongdouble=undef
  usemymalloc=n, bincompat5005=undef
  Compiler​:
  cc='cc', ccflags ='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
  optimize='-O2',
  cppflags='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include'
  ccversion='', gccversion='4.4.3', gccosandvers=''
  intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
  d_longlong=define, longUse of uninitialized value $category in
concatenation (.) or string at /usr/local/bin/perlbug line 645.
Use of uninitialized value $severity in concatenation (.) or string at
/usr/local/bin/perlbug line 645.

---

Flags​:
  category=
  severity=high

---

Site configuration information for perl 5.12.0​:

Configured by eof at Tue May 11 08​:12​:38 BRT 2010.

Summary of my perl5 (revision 5 version 12 subversion 0) configuration​:

  Platform​:
  osname=linux, osvers=2.6.32-22-generic, archname=i686-linux
  uname='linux golden-eagle 2.6.32-22-generic #33-ubuntu smp wed apr 28
13​:27​:30 utc 2010 i686 gnulinux '
  config_args='-de'
  hint=recommended, useposix=true, d_sigaction=define
  useithreads=undef, usemultiplicity=undef
  useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
  use64bitint=undef, use64bitall=undef, uselongdouble=undef
  usemymalloc=n, bincompat5005=undef
  Compiler​:
  cc='cc', ccflags ='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
  optimize='-O2',
  cppflags='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include'
  ccversion='', gccversion='4.4.3', 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='cc', ldflags =' -fstack-protector -L/usr/local/lib'
  libpth=/usr/local/lib /lib /usr/lib /usr/lib64
  libs=-lnsl -ldl -lm -lcrypt -lutil -lc
  perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
  libc=/lib/libc-2.11.1.so, so=so, useshrplib=false, libperl=libperl.a
  gnulibc_version='2.11.1'
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
  cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib
-fstack-protector'

Locally applied patches​:

---

@​INC for perl 5.12.0​:
  /usr/local/lib/perl5/site_perl/5.12.0/i686-linux
  /usr/local/lib/perl5/site_perl/5.12.0
  /usr/local/lib/perl5/5.12.0/i686-linux
  /usr/local/lib/perl5/5.12.0
  .

---

Environment for perl 5.12.0​:
  HOME=/home/eof
  LANG=en_US.utf8
  LANGUAGE (unset)
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)

PATH=/usr/local/sbin​:/usr/local/bin​:/usr/sbin​:/usr/bin​:/sbin​:/bin​:/usr/games
  PERL_BADLANG (unset)
  SHELL=/bin/bashlongsize=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='cc', ldflags =' -fstack-protector -L/usr/local/lib'
  libpth=/usr/local/lib /lib /usr/lib /usr/lib64
  libs=-lnsl -ldl -lm -lcrypt -lutil -lc
  perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
  libc=/lib/libc-2.11.1.so, so=so, useshrplib=false, libperl=libperl.a
  gnulibc_version='2.11.1'
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
  cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib
-fstack-protector'

Locally applied patches​:

---

@​INC for perl 5.12.0​:
  /usr/local/lib/perl5/site_perl/5.12.0/i686-linux
  /usr/local/lib/perl5/site_perl/5.12.0
  /usr/local/lib/perl5/5.12.0/i686-linux
  /usr/local/lib/perl5/5.12.0
  .

---

Environment for perl 5.12.0​:
  HOME=/home/eof
  LANG=en_US.utf8
  LANGUAGE (unset)
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)

PATH=/usr/local/sbin​:/usr/local/bin​:/usr/sbin​:/usr/bin​:/sbin​:/bin​:/usr/games
  PERL_BADLANG (unset)
  SHELL=/bin/bash

--
Hudson Flávio Vieira Mateus
7° período - Ciência da Computação
Universidade Federal de Lavras

Linux registered user #488195

[p5pRT]

From @rgarcia

2010/5/18 Hudson Flávio Vieira Mateus <perlbug-followup@​perl.org>​:

Hello.

I tried to run the follow script, but I get wrong result.

I checked it, I think is correct.

Smarts matches in lines 12 and 16 doesn't work as expected. This piece of
code is part of a largest program, but this piece gives a wrong answer to me
(all numbers are odd!).

Hugs! Thanks by attention.

Case of test used​:
----------------------------------------------
1  #!/usr/bin/perl
2
3  use 5.010;
4
5  print "Enter number​: ";
6  chomp($number = <STDIN>) while (!($number ~~ /^\s*(0|[1-9]+)\s*$/));
7
8  @​divisors = &getdivisors($number);
9
10 say "Divisors​: @​divisors";
11 given( $number ) {
12     when( @​divisors ~~ 2 ) {

You want if() there, not when(), because $number is not used in your condition.
Also, to test correctly, you should invert the operands :
if (2 ~~ @​divisors) ...
This is described in more detail in the perlsyn man page.

13         say "$_ is a even number.";
14         continue;
15     }
16     when( !(@​divisors ~~ 2) ) {
17         say "$_ is a odd number.";
18     }
19 }
20
21 sub getdivisors {
22     my ($div, @​divisors) = (1);
23
24     while ($div <= $_[0]) {
25         push(@​divisors, $div) unless ($_[0] % $div);
26         ++$div;
27     }
28
29    return @​divisors;
30 }
----------------------------------------------

Use of uninitialized value $category in concatenation (.) or string at
/usr/local/bin/perlbug line 645.
Use of uninitialized value $severity in concatenation (.) or string at
/usr/local/bin/perlbug line 645.
---
Flags​:
   category=?
   severity=high
---
Site configuration information for perl 5.12.0​:

Configured by eof at Tue May 11 08​:12​:38 BRT 2010.

Summary of my perl5 (revision 5 version 12 subversion 0) configuration​:

 Platform​:
   osname=linux, osvers=2.6.32-22-generic, archname=i686-linux
   uname='linux golden-eagle 2.6.32-22-generic #33-ubuntu smp wed apr 28
13​:27​:30 utc 2010 i686 gnulinux '
   config_args='-de'
   hint=recommended, useposix=true, d_sigaction=define
   useithreads=undef, usemultiplicity=undef
   useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
   use64bitint=undef, use64bitall=undef, uselongdouble=undef
   usemymalloc=n, bincompat5005=undef
 Compiler​:
   cc='cc', ccflags ='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
   optimize='-O2',
   cppflags='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include'
   ccversion='', gccversion='4.4.3', gccosandvers=''
   intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
   d_longlong=define, longUse of uninitialized value $category in
concatenation (.) or string at /usr/local/bin/perlbug line 645.
Use of uninitialized value $severity in concatenation (.) or string at
/usr/local/bin/perlbug line 645.
---
Flags​:
   category=
   severity=high
---
Site configuration information for perl 5.12.0​:

Configured by eof at Tue May 11 08​:12​:38 BRT 2010.

Summary of my perl5 (revision 5 version 12 subversion 0) configuration​:

 Platform​:
   osname=linux, osvers=2.6.32-22-generic, archname=i686-linux
   uname='linux golden-eagle 2.6.32-22-generic #33-ubuntu smp wed apr 28
13​:27​:30 utc 2010 i686 gnulinux '
   config_args='-de'
   hint=recommended, useposix=true, d_sigaction=define
   useithreads=undef, usemultiplicity=undef
   useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
   use64bitint=undef, use64bitall=undef, uselongdouble=undef
   usemymalloc=n, bincompat5005=undef
 Compiler​:
   cc='cc', ccflags ='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
   optimize='-O2',
   cppflags='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include'
   ccversion='', gccversion='4.4.3', 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='cc', ldflags =' -fstack-protector -L/usr/local/lib'
   libpth=/usr/local/lib /lib /usr/lib /usr/lib64
   libs=-lnsl -ldl -lm -lcrypt -lutil -lc
   perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
   libc=/lib/libc-2.11.1.so, so=so, useshrplib=false, libperl=libperl.a
   gnulibc_version='2.11.1'
 Dynamic Linking​:
   dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
   cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib
-fstack-protector'

Locally applied patches​:

---
@​INC for perl 5.12.0​:
   /usr/local/lib/perl5/site_perl/5.12.0/i686-linux
   /usr/local/lib/perl5/site_perl/5.12.0
   /usr/local/lib/perl5/5.12.0/i686-linux
   /usr/local/lib/perl5/5.12.0
   .

---
Environment for perl 5.12.0​:
   HOME=/home/eof
   LANG=en_US.utf8
   LANGUAGE (unset)
   LD_LIBRARY_PATH (unset)
   LOGDIR (unset)

PATH=/usr/local/sbin​:/usr/local/bin​:/usr/sbin​:/usr/bin​:/sbin​:/bin​:/usr/games
   PERL_BADLANG (unset)
   SHELL=/bin/bashlongsize=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='cc', ldflags =' -fstack-protector -L/usr/local/lib'
   libpth=/usr/local/lib /lib /usr/lib /usr/lib64
   libs=-lnsl -ldl -lm -lcrypt -lutil -lc
   perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
   libc=/lib/libc-2.11.1.so, so=so, useshrplib=false, libperl=libperl.a
   gnulibc_version='2.11.1'
 Dynamic Linking​:
   dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
   cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib
-fstack-protector'

Locally applied patches​:

---
@​INC for perl 5.12.0​:
   /usr/local/lib/perl5/site_perl/5.12.0/i686-linux
   /usr/local/lib/perl5/site_perl/5.12.0
   /usr/local/lib/perl5/5.12.0/i686-linux
   /usr/local/lib/perl5/5.12.0
   .

---
Environment for perl 5.12.0​:
   HOME=/home/eof
   LANG=en_US.utf8
   LANGUAGE (unset)
   LD_LIBRARY_PATH (unset)
   LOGDIR (unset)

PATH=/usr/local/sbin​:/usr/local/bin​:/usr/sbin​:/usr/bin​:/sbin​:/bin​:/usr/games
   PERL_BADLANG (unset)
   SHELL=/bin/bash

--
Hudson Flávio Vieira Mateus
7° período - Ciência da Computação
Universidade Federal de Lavras

Linux registered user #488195

--
"You don't mean odds and ends, you mean des curieux et des bouts",
corrected the manager.
-- Terry Pratchett, Hogfather

[p5pRT]

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

[p5pRT]

@rgs - Status changed from 'open' to 'rejected'

[p5pRT]

From [email protected]

I've tested others cases and $number is used.

Anyway, try this​:

use 5.010;

$number = 2;

given ($number) {
  when (2) {
  say "2 here!";
  }
}

Well, I've seen in a book ("Learning Perl - Fifth Edition") that smart match
is comutative.

So, this another example too​:

use 5.010;

@​array = (1,2,3);

if (@​array ~~ 2) {
  say "Matched!";
}

This e-mail was tested in 5.10. First e-mail was tested in 5.12 too and
didn't work.

Hugs!

--
Hudson Flávio Vieira Mateus
7° período - Ciência da Computação
Universidade Federal de Lavras

Linux registered user #488195

[p5pRT]

From @rgarcia

On 18 May 2010 15​:18, Hudson Flavio V Mateus <hudson@​comp.ufla.br> wrote​:

I've tested others cases and $number is used.

Anyway, try this​:

use 5.010;

$number = 2;

given ($number) {
   when (2) {
       say "2 here!";
   }
}

Well, I've seen in a book ("Learning Perl - Fifth Edition") that smart match
is comutative.

No, it's not. It was in 5.10.0, but that caused problems, so in some
cases it's no longer commutative in 5.10.1 and 5.12.*. The perl
documentation remains the authoritative source for perl's behaviour.

[p5pRT]

From [email protected]

Really, sometimes works, sometimes no... =/

Thanks by attention!

On Tue, May 18, 2010 at 12​:14 PM, Rafael Garcia-Suarez <rgs@​consttype.org>wrote​:

On 18 May 2010 15​:18, Hudson Flavio V Mateus <hudson@​comp.ufla.br> wrote​:

I've tested others cases and $number is used.

Anyway, try this​:

use 5.010;

$number = 2;

given ($number) {
when (2) {
say "2 here!";
}
}

Well, I've seen in a book ("Learning Perl - Fifth Edition") that smart
match
is comutative.

No, it's not. It was in 5.10.0, but that caused problems, so in some
cases it's no longer commutative in 5.10.1 and 5.12.*. The perl
documentation remains the authoritative source for perl's behaviour.

--
Hudson Flávio Vieira Mateus
7° período - Ciência da Computação
Universidade Federal de Lavras

Linux registered user #488195

[p5pRT]

From @ikegami

On Tue, May 18, 2010 at 11​:43 AM, Hudson Flavio V Mateus <
hudson@​comp.ufla.br> wrote​:

Really, sometimes works, sometimes no... =/

It always works if the arguments are ordered as per the 5.10.1 and newer
documentation. Non-commutative functions aren't exactly rare. 2**3 is not
the same as 3**2, and f() || g() is not the same as g() || f().

There was a whole class of problems that could only be solved by removing
the commutativity. Sorry for the inconvenience that this change caused.

[p5pRT]

From [email protected]

"It always works if the arguments are ordered as per the 5.10.1 and newer
documentation. Non-commutative functions aren't exactly rare. 2**3 is not
the same as 3**2, and f() || g() is not the same as g() || f()."

Oh, yes. I agree with you in *this case*. But, in case of Perl smart match
~~, documentation Perl *5.10*, not .1 or newer, says that the order that I
was using was correct. See more​: <
http​://perldoc.perl.org/5.10.0/perlsyn.html#Switch-statements>, section
"Smart matching in detail". There says exactly "It is *always commutative*".

But take this out.

Thanks by attention!

On Wed, May 19, 2010 at 11​:43 AM, Eric Brine <ikegami@​adaelis.com> wrote​:

On Tue, May 18, 2010 at 11​:43 AM, Hudson Flavio V Mateus <
hudson@​comp.ufla.br> wrote​:

Really, sometimes works, sometimes no... =/

It always works if the arguments are ordered as per the 5.10.1 and newer
documentation. Non-commutative functions aren't exactly rare. 2**3 is not
the same as 3**2, and f() || g() is not the same as g() || f().

There was a whole class of problems that could only be solved by removing
the commutativity. Sorry for the inconvenience that this change caused.

--
Hudson Flávio Vieira Mateus
7° período - Ciência da Computação
Universidade Federal de Lavras

Linux registered user #488195