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qw and x operator #763

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p5pRT opened this issue Oct 22, 1999 · 1 comment
Closed

qw and x operator #763

p5pRT opened this issue Oct 22, 1999 · 1 comment

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@p5pRT
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@p5pRT p5pRT commented Oct 22, 1999

Migrated from rt.perl.org#1687 (status was 'resolved')

Searchable as RT1687$

@p5pRT
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@p5pRT p5pRT commented Oct 22, 1999

From marcel.grunauer@lovely.net

I've come across a behavior of the qw() operator in conjunction with
the x operator that I can't explain. I've checked perlop.

#!/usr/bin/perl -w
use strict;
my %test;
@​test{qw/a b c/} = ('n') x 3;
print "$_ => $test{$_}\n" foreach keys %test;

produces, as expected​:

a => n
b => n
c => n

If I replace the hash slice line above with

@​test{qw/a b c/} = qw/n/ x 3;

it produces​:

Bareword "x" not allowed while "strict subs" in use at ...
Unquoted string "x" may clash with future reserved word at ...
syntax error at ..., near "qw/n/ x "
Number found where operator expected at ..., near "x 3"
  (Do you need to predeclare x?)

The following two work ok​:

@​test{qw/a b c/} = (qw/n/) x 3;
@​test{qw/a b c/} = (split(' ', q/n/)) x 3;

According to Tad McClellan (tadmc@​metronet.com)​:

Note also that you get the same messages if you replace the
line above with just​:

x 3;

Looks like perl is taking "@​test{qw/a b c/} = qw/n/" as an
entire statement, and then resuming the parse...

According to Abigail (abigail@​delanet.com)​:

Based on [the repetition operator documentation], I would assume that

@​test\{qw/a b c/\} = qw/n/ x 3;

would lead to​:

%test = \(a => '111'\, b => undef\, c => undef\);

This is because the left operand of x will be evaluated in scalar context,
hence the split qw// does is done to @​_, and the amount of produced fields
is returned. This being 1, leads to 1 x 3 which is '111'.


Site configuration information for perl 5.00502​:

Summary of my perl5 (5.0 patchlevel 5 subversion 02) configuration​:
  Platform​:
  osname=MSWin32, osvers=4.0, archname=MSWin32-x86-object
  uname=''
  hint=recommended, useposix=true, d_sigaction=undef
  usethreads=undef useperlio=undef d_sfio=undef
  Compiler​:
  cc='cl.exe', optimize='-O2 -MD -DNDEBUG -TP -GX', gccversion=
  cppflags='-DWIN32'
  ccflags ='-O2 -MD -DNDEBUG -TP -GX -DWIN32 -D_CONSOLE -DNO_STRICT
-DHAVE_DES_FCRYPT -DPERL_OBJECT'
  stdchar='char', d_stdstdio=define, usevfork=false
  intsize=4, longsize=4, ptrsize=4, doublesize=8
  d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=10
  alignbytes=8, usemymalloc=n, prototype=define
  Linker and Libraries​:
  ld='link', ldflags ='-nologo -nodefaultlib -release -machine​:x86'
  libpth="C​:\usr\lib\core" "C​:\Program Files\Mts\Lib"
  libs= oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib
comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib
netapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib version.lib
odbc32.lib odbccp32.lib PerlCRT.lib
  libc=C​:\usr\lib\core\PerlCRT.lib, so=dll, useshrplib=yes,
libperl=perlcore.lib
  Dynamic Linking​:
  dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
  cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -release
-machine​:x86'

Locally applied patches​:
  ACTIVEPERL_LOCAL_PATCHES_ENTRY


@​INC for perl 5.00502​:
  C​:\root\perldev\lib
  C​:\usr\lib
  C​:\usr\site\lib
  .


Environment for perl 5.00502​:
  HOME=C​:\root
  LANG (unset)
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)

PATH=c​:\cygnus\CYGWIN1\H-I5861\bin;.;C​:\usr\bin;C​:\WINNT\system32;C​:\WINNT;C​:\rootbin;c​:\cygnus\CYGWIN1\H-I5861\bin;G​:\jdk1.2.2\bin;c​:\Program
Files\Winzip;C​:\DAYNA
  PERL5LIB=C​:\root\perldev\lib
  PERL_BADLANG (unset)
  SHELL=/bin/sh

--
Marcel, Perl Padawan
sub AUTOLOAD{$_=$AUTOLOAD;s;.*​::;;;y;_; ;;print}&Just_Another_Perl_Hacker;

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