From the.rob.dixon@gmail.com

This is a bug report for perl from the.rob.dixon@​gmail.com,
generated with the help of perlbug 1.40 running under perl 5.20.0.

I notice that

  ($x, $y) = split

is usefully optimised to

  ($x, $y) = split(' ', $_, 3)

and I wonder how hard it would be to do something similar by changing

  $x = (split)[3]

to

  $x = (split ' ', $_, 4)[3]

because at present this is most efficiently coded as the ugly

  (undef, undef, undef, $x) = split;

Flags​:
  category=core
  severity=wishlist

Site configuration information for perl 5.20.0​:

Configured by strawberry-perl at Fri May 30 23​:27​:10 2014.

Summary of my perl5 (revision 5 version 20 subversion 0) configuration​:

  Platform​:
  osname=MSWin32, osvers=6.2, archname=MSWin32-x86-multi-thread-64int
  uname='Win32 strawberry-perl 5.20.0.1 #1 Fri May 30 23​:25​:11 2014 i386'
  config_args='undef'
  hint=recommended, useposix=true, d_sigaction=undef
  useithreads=define, usemultiplicity=define
  use64bitint=define, use64bitall=undef, uselongdouble=undef
  usemymalloc=n, bincompat5005=undef
  Compiler​:
  cc='gcc', ccflags =' -s -O2 -DWIN32 -DPERL_TEXTMODE_SCRIPTS
-DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -DUSE_PERLIO -fwrapv
-fno-strict-aliasing -mms-bitfields',
  optimize='-s -O2',
  cppflags='-DWIN32'
  ccversion='', gccversion='4.8.2', gccosandvers=''
  intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=12345678
  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
  ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='long
long', lseeksize=8
  alignbytes=8, prototype=define
  Linker and Libraries​:
  ld='g++', ldflags ='-s -L"C​:\STRAWB3\perl\lib\CORE"
-L"C​:\STRAWB3\c\lib"'
  libpth=C​:\STRAWB3\c\lib C​:\STRAWB3\c\i686-w64-mingw32\lib
C​:\STRAWB3\c\lib\gcc\i686-w64-mingw32\4.8.2
  libs=-lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32
-ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr
-lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32
  perllibs=-lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32
-ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr
-lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32
  libc=, so=dll, useshrplib=true, libperl=libperl520.a
  gnulibc_version=''
  Dynamic Linking​:
  dlsrc=dl_win32.xs, dlext=xs.dll, d_dlsymun=undef, ccdlflags=' '
  cccdlflags=' ', lddlflags='-mdll -s -L"C​:\STRAWB3\perl\lib\CORE"
-L"C​:\STRAWB~3\c\lib"'

@​INC for perl 5.20.0​:
  C​:/Strawberry/perl/site/lib/MSWin32-x86-multi-thread-64int
  C​:/Strawberry/perl/site/lib
  C​:/Strawberry/perl/vendor/lib
  C​:/Strawberry/perl/lib
  .

Environment for perl 5.20.0​:
  HOME (unset)
  LANG (unset)
  LANGUAGE (unset)
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)
  PATH=C​:\Program Files (x86)\ImageMagick-6.8.3-Q16;C​:\Program
Files\ImageMagick-6.8.3-Q16;C​:\Program Files (x86)\NVIDIA
Corporation\PhysX\Common;C​:\Program Files (x86)\PC Connectivity
Solution\;C​:\Program Files\Common Files\Microsoft Shared\Windows
Live;C​:\Program Files
(x86)\PHP\;C​:\Windows\system32;C​:\Windows;C​:\Windows\System32\Wbem;C​:\Windows\System32\WindowsPowerShell\v1.0\;C​:\Program
Files\jEdit;C​:\usr\local\ppt\bin;C​:\Program Files
(x86)\GnuWin32\bin;C​:\Program Files (x86)\Smart
Projects\IsoBuster;C​:\Program Files (x86)\Oracle\Berkeley DB 11gR2
5.3.15\bin;C​:\Program Files (x86)\Git\cmd;C​:\Program Files
(x86)\Bazaar;C​:\Program Files (x86)\Lua\5.1;C​:\Program Files
(x86)\Lua\5.1\clibs;C​:\Program
Files\TortoiseSVN\bin;C​:\MediaInfoCLI;C​:\Program Files
(x86)\MKVToolNix;C​:\Program Files (x86)\Subversion\bin;C​:\Program Files
(x86)\Common Files\Ulead Systems\MPEG;C​:\Program Files
(x86)\QuickTime\QTSystem\;C​:\Program Files\Microsoft Network Monitor
3\;C​:\Program Files\Calibre2\;C​:\Program Files (x86)\MySQL\MySQL Utilities
1.3.4\;C​:\Program Files (x86)\Common Files\Acronis\SnapAPI\;C​:\Program
Files (x86)\Windows Kits\8.1\Windows Performance Toolkit\;C​:\Program
Files\Microsoft SQL Server\110\Tools\Binn\;C​:\Program Files (x86)\Microsoft
SDKs\TypeScript\1.0\;C​:\Strawberry\c\bin;C​:\Strawberry\perl\site\bin;C​:\Strawberry\perl\bin;C​:\SQLite;C​:\Program
Files\WinRAR;C​:\Program Files\Common Files\Microsoft Shared\Windows
Live;C​:\Program Files (x86)\Common Files\Hackety Hack\0.r1529\..;C​:\Program
Files (x86)\IDM Computer Solutions\UltraCompare\;C​:\ffmpeg\bin;C​:\Program
Files (x86)\Serviio\lib;C​:\Program Files (x86)\Microsoft Visual Studio
10.0\VC\bin\x86_amd64;C​:\Program Files (x86)\Microsoft Visual Studio
10.0\VC\bin\amd64;C​:\SWIG;C​:\MinGW\bin;C​:\MinGW\MSYS\1.0\bin;C​:\Python27;C​:\Curl;C​:\pkg-config\bin;C​:\glib\bin;C​:\gettext-runtime\bin;C​:\Program
Files (x86)\IDM Computer Solutions\UltraEdit\;C​:\LuaRocks\2.0;C​:\Program
Files
(x86)\Android\android-sdk\platform-tools;C​:\Ruby193\bin;C​:\Ruby193.DevKit\bin;C​:\Program
Files (x86)\Nmap;C​:\MobiPerl;E​:\Perl\source;C​:\Program Files
(x86)\EaseUS\Todo Backup\bin\x64\
  PERL_BADLANG (unset)
  SHELL (unset)

From @cpansprout

On Sun Jun 08 14​:53​:33 2014, the.rob.dixon@​gmail.com wrote​:

This is a bug report for perl from the.rob.dixon@​gmail.com,
generated with the help of perlbug 1.40 running under perl 5.20.0.

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

I notice that

($x, $y) = split

is usefully optimised to

($x, $y) = split(' ', $_, 3)

and I wonder how hard it would be to do something similar by changing

$x = (split)[3]

to

$x = (split ' ', $_, 4)[3]

because at present this is most efficiently coded as the ugly

(undef, undef, undef, $x) = split;

But adding an implicit limit changes the behaviour​:

$ perl -le 'print "[",$_//"undef","]" for (split /,/, "a,,,,,,")[3]'
$ perl -le 'print "[",$_//"undef","]" for (split /,/, "a,,,,,,", 5)[3]'
[]

And fixing the existing optimisation to be a pure optimisation is controversial. See ticket #118879.

--

Father Chrysostomos

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