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authorPerl 5 Porters <perl5-porters@africa.nicoh.com>1996-12-19 16:44:00 +1200
committerChip Salzenberg <chip@atlantic.net>1996-12-19 16:44:00 +1200
commit5f05dabc4054964aa3b10f44f8468547f051cdf8 (patch)
tree7bcc2c7b6d5cf44e7f0111bac2240ca979d9c804 /pod/perlref.pod
parent6a3992aa749356d657a4c0e14be8c2f4c2f4f999 (diff)
downloadperl-5f05dabc4054964aa3b10f44f8468547f051cdf8.tar.gz
[inseparable changes from patch from perl5.003_11 to perl5.003_12]
CORE LANGUAGE CHANGES Subject: Support C<delete @hash{@keys}> From: Chip Salzenberg <chip@atlantic.net> Files: op.c op.h opcode.pl pod/perldiag.pod pod/perlfunc.pod pp.c t/op/delete.t Subject: Autovivify scalars From: Chip Salzenberg <chip@atlantic.net> Files: dump.c op.c op.h pp.c pp_hot.c DOCUMENTATION Subject: Update pods: perldelta -> perlnews, perli18n -> perllocale From: Tom Christiansen <tchrist@perl.com> Files: MANIFEST pod/perl.pod pod/perldelta.pod pod/perli18n.pod pod/perlnews.pod Subject: perltoot.pod Date: Mon, 09 Dec 1996 07:44:10 -0700 From: Tom Christiansen <tchrist@mox.perl.com> Files: MANIFEST pod/perltoot.pod Msg-ID: <199612091444.HAA09947@toy.perl.com> (applied based on p5p patch as commit 32e22efaa9ec59b73a208b6c532a0b435e2c6462) Subject: Perlguts, version 25 Date: Fri, 6 Dec 96 11:40:27 PST From: Jeff Okamoto <okamoto@hpcc123.corp.hp.com> Files: pod/perlguts.pod private-msgid: <199612061940.AA055461228@hpcc123.corp.hp.com> Subject: pod patches for English errors Date: Mon, 09 Dec 1996 13:33:11 -0800 From: Steve Kelem <steve.kelem@xilinx.com> Files: pod/*.pod Msg-ID: <24616.850167191@castor> (applied based on p5p patch as commit 0135f10892ed8a21c4dbd1fca21fbcc365df99dd) Subject: Misc doc updates Date: Sat, 14 Dec 1996 18:56:33 -0700 From: Tom Christiansen <tchrist@mox.perl.com> Files: pod/* Subject: Re: perldelta.pod Here are some diffs to the _11 pods. I forgot to add perldelta to perl.pod though. And *PLEASE* fix the Artistic License so it no longer has the bogus "whomever" misdeclined in the nominative case: under the copyright of this Package, but belong to whomever generated them, and may be sold commercially, and may be aggregated with this It should obviously be "whoever". p5p-msgid: <199612150156.SAA12506@mox.perl.com> OTHER CORE CHANGES Subject: Allow assignment to empty array values during foreach() From: Chip Salzenberg <chip@atlantic.net> Files: cop.h global.sym mg.c op.c perl.h pp_hot.c proto.h sv.c Subject: Fix nested closures From: Chip Salzenberg <chip@atlantic.net> Files: op.c opcode.pl pp.c pp_ctl.c pp_hot.c Subject: Fix core dump on auto-vivification From: Chip Salzenberg <chip@atlantic.net> Files: pp_hot.c Subject: Fix core dump on C<open $undef_var, "X"> From: Chip Salzenberg <chip@atlantic.net> Files: pp_sys.c Subject: Fix -T/-B on globs and globrefs From: Chip Salzenberg <chip@atlantic.net> Files: pp_sys.c Subject: Fix memory management of $`, $&, and $' From: Chip Salzenberg <chip@atlantic.net> Files: pp_hot.c regexec.c Subject: Fix paren matching during backtracking From: Chip Salzenberg <chip@atlantic.net> Files: regexec.c Subject: Fix memory leak and std{in,out,err} death in perl_{con,de}str From: Chip Salzenberg <chip@atlantic.net> Files: miniperlmain.c perl.c perl.h sv.c Subject: Discard garbage bytes at end of prototype() From: Chip Salzenberg <chip@atlantic.net> Files: pp.c Subject: Fix local($pack::{foo}) From: Chip Salzenberg <chip@atlantic.net> Files: global.sym pp.c pp_hot.c proto.h scope.c Subject: Disable warn, die, and parse hooks _before_ global destruction From: Chip Salzenberg <chip@atlantic.net> Files: perl.c Subject: Re: Bug in formline Date: Sun, 08 Dec 1996 14:58:32 -0500 From: Gurusamy Sarathy <gsar@engin.umich.edu> Files: pp_ctl.c Msg-ID: <199612081958.OAA26025@aatma.engin.umich.edu> (applied based on p5p patch as commit b386bda18108ba86d0b76ebe2d8745eafa80f39e) Subject: Fix C<@a = ($a,$b,$c,$d) = (1,2)> From: Chip Salzenberg <chip@atlantic.net> Files: pp_hot.c Subject: Properly support and document newRV{,_inc,_noinc} From: Chip Salzenberg <chip@atlantic.net> Files: global.sym pod/perlguts.pod sv.c sv.h Subject: Allow lvalue pos inside recursive function From: Chip Salzenberg <chip@atlantic.net> Files: op.c pp.c pp_ctl.c pp_hot.c PORTABILITY Subject: Make $privlib contents compatible with 5.003 From: Chip Salzenberg <chip@atlantic.net> Files: INSTALL ext/Opcode/Safe.pm installperl lib/FileHandle.pm lib/Test/Harness.pm Subject: Support $bincompat3 config variable; update metaconfig units From: Chip Salzenberg <chip@atlantic.net> Files: Configure MANIFEST compat3.sym config_h.SH embed.pl global.sym old_embed.pl old_global.sym old_perl_exp.SH perl_exp.SH Subject: Look for gettimeofday() in Configure Date: Wed, 11 Dec 1996 15:49:57 +0100 From: John Hughes <john@AtlanTech.COM> Files: Configure config_H config_h.SH pp.c Subject: perl5.003_11, Should base use of gettimeofday on HAS_GETTIMEOFDAY, not I_SYS_TIME I've been installing perl5.003_11 on a SCO system that has the TCP/IP runtime installed but not the TCP/IP development system. Unfortunately the <sys/time.h> include file is included in the TCP/IP runtime while libsocket.a is in the development system. This means that pp.c decides to use "gettimeofday" because <sys/time.h> is present but I can't link the perl that gets compiled. So, here's a patch to base the use of "gettimeofday" on "HAS_GETTIMEOFDAY" instead of "I_SYS_TIME". I also took the liberty of removing the special case for plan9 (I assume plan9 has <sys/time.h> but no gettimeofday. Am I right?). p5p-msgid: <01BBE77A.F6F37F80@malvinas.AtlanTech.COM> Subject: Make $startperl a relative path if people want portable scrip From: Chip Salzenberg <chip@atlantic.net> Files: Configure Subject: Homogenize use of "eval exec" hack From: Chip Salzenberg <chip@atlantic.net> Files: Porting/Glossary eg/README eg/nih eg/sysvipc/ipcmsg eg/sysvipc/ipcsem eg/sysvipc/ipcshm lib/diagnostics.pm makeaperl.SH pod/checkpods.PL pod/perlrun.pod pod/pod2html.PL pod/pod2latex.PL pod/pod2man.PL pod/pod2text.PL utils/c2ph.PL utils/h2ph.PL utils/h2xs.PL utils/perlbug.PL utils/perldoc.PL utils/pl2pm.PL x2p/a2py.c x2p/find2perl.PL x2p/s2p.PL Subject: LynxOS support Date: Thu, 12 Dec 1996 09:25:00 PST From: Greg Seibert <seibert@Lynx.COM> Files: Configure MANIFEST hints/lynxos.sh t/op/stat.t Msg-ID: <m0vYEsY-0000IZC@kzinti.lynx.com> (applied based on p5p patch as commit 6693373533b15e559fd8f0f1877e5e6ec15483cc) Subject: Re: db-recno.t failures with _11 on Freebsd 2.1-stable Date: 11 Dec 1996 18:58:56 -0500 From: Roderick Schertler <roderick@gate.net> Files: INSTALL hints/freebsd.sh Msg-ID: <pzohg0r5tr.fsf@eeyore.ibcinc.com> (applied based on p5p patch as commit 10e40321ee752c58e3407b204c74c8049894cb51) Subject: VMS patches to 5.003_11 Date: Mon, 09 Dec 1996 23:16:10 -0500 (EST) From: Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU> Files: MANIFEST regexec.c t/lib/filehand.t util.c vms/* private-msgid: <01ICTR32LCZG001A1D@hmivax.humgen.upenn.edu> TESTING Subject: recurse recurse recurse ... Date: Mon, 9 Dec 1996 23:44:27 +0200 (EET) From: Jarkko Hietaniemi <jhi@cc.hut.fi> Files: MANIFEST t/op/recurse.t private-msgid: <199612092144.XAA29025@alpha.hut.fi> UTILITIES, LIBRARY, AND EXTENSIONS Subject: Add CPAN and Net::FTP From: Chip Salzenberg <chip@atlantic.net> Files: MANIFEST lib/CPAN.pm lib/CPAN/FirstTime.pm lib/CPAN/Nox.pm lib/Net/FTP.pm lib/Net/Netrc.pm lib/Net/Socket.pm pod/perlmod.pod Subject: Add File::Compare Date: Mon, 16 Dec 1996 18:44:59 GMT From: Nick Ing-Simmons <nik@tiuk.ti.com> Files: MANIFEST lib/File/Compare.pm pod/perlmod.pod Msg-ID: <199612161844.SAA02152@pluto> (applied based on p5p patch as commit ec971c5c328aca84fb827f69f2cc1dc3be81f830) Subject: Add Tie::RefHash Date: Sun, 15 Dec 1996 18:58:08 -0500 From: Gurusamy Sarathy <gsar@engin.umich.edu> Files: MANIFEST lib/Tie/RefHash.pm pod/perlmod.pod Msg-ID: <199612152358.SAA28665@aatma.engin.umich.edu> (applied based on p5p patch as commit 9a079709134ebbf4c935cc8752fdb564e5c82b94) Subject: Put "splain" in utils. From: Chip Salzenberg <chip@atlantic.net> Files: Makefile.SH installperl utils/Makefile utils/splain.PL Subject: Some h2ph fixes Date: Fri, 13 Dec 1996 11:34:12 -0800 From: Jeff Okamoto <okamoto@hpcc123.corp.hp.com> Files: utils/h2ph.PL Here is a message regarding changes to h2ph that should probably be folded into the 5.004 release. p5p-msgid: <199612131934.AA289845652@hpcc123.corp.hp.com>
Diffstat (limited to 'pod/perlref.pod')
-rw-r--r--pod/perlref.pod50
1 files changed, 33 insertions, 17 deletions
diff --git a/pod/perlref.pod b/pod/perlref.pod
index 5303c3a12a..bbbe57feba 100644
--- a/pod/perlref.pod
+++ b/pod/perlref.pod
@@ -7,9 +7,9 @@ perlref - Perl references and nested data structures
Before release 5 of Perl it was difficult to represent complex data
structures, because all references had to be symbolic, and even that was
difficult to do when you wanted to refer to a variable rather than a
-symbol table entry. Perl 5 not only makes it easier to use symbolic
+symbol table entry. Perl not only makes it easier to use symbolic
references to variables, but lets you have "hard" references to any piece
-of data. Any scalar may hold a hard reference. Since arrays and hashes
+of data. Any scalar may hold a hard reference. Because arrays and hashes
contain scalars, you can now easily build arrays of arrays, arrays of
hashes, hashes of arrays, arrays of hashes of functions, and so on.
@@ -25,7 +25,7 @@ references to objects that have been officially "blessed" into a class package.)
A symbolic reference contains the name of a variable, just as a
-symbolic link in the filesystem merely contains the name of a file.
+symbolic link in the filesystem contains merely the name of a file.
The C<*glob> notation is a kind of symbolic reference. Hard references
are more like hard links in the file system: merely another way
at getting at the same underlying object, irrespective of its name.
@@ -44,7 +44,7 @@ References can be constructed several ways.
By using the backslash operator on a variable, subroutine, or value.
(This works much like the & (address-of) operator works in C.) Note
-that this typically creates I<ANOTHER> reference to a variable, since
+that this typically creates I<ANOTHER> reference to a variable, because
there's already a reference to the variable in the symbol table. But
the symbol table reference might go away, and you'll still have the
reference that the backslash returned. Here are some examples:
@@ -55,9 +55,11 @@ reference that the backslash returned. Here are some examples:
$coderef = \&handler;
$globref = \*foo;
-It isn't possible to create a reference to an IO handle (filehandle or
+It isn't possible to create a true reference to an IO handle (filehandle or
dirhandle) using the backslash operator. See the explanation of the
-*foo{THING} syntax below.
+*foo{THING} syntax below. (However, you're apt to find Perl code
+out there using globrefs as though they were IO handles, which is
+grandfathered into continued functioning.)
=item 2.
@@ -167,7 +169,7 @@ newprint() I<despite> the fact that the "my $x" has seemingly gone out of
scope by the time the anonymous subroutine runs. That's what closure
is all about.
-This only applies to lexical variables, by the way. Dynamic variables
+This applies to only lexical variables, by the way. Dynamic variables
continue to work as they have always worked. Closure is not something
that most Perl programmers need trouble themselves about to begin with.
@@ -186,7 +188,7 @@ named new(), but don't have to be:
=item 6.
References of the appropriate type can spring into existence if you
-dereference them in a context that assumes they exist. Since we haven't
+dereference them in a context that assumes they exist. Because we haven't
talked about dereferencing yet, we can't show you any examples yet.
=item 7.
@@ -209,8 +211,13 @@ IO handle, used for file handles (L<perlfunc/open>), sockets
(L<perlfunc/opendir>). For compatibility with previous versions of
Perl, *foo{FILEHANDLE} is a synonym for *foo{IO}.
-The use of *foo{IO} is the best way to pass bareword filehandles into
-or out of subroutines, or to store them in larger data structures.
+*foo{THING} returns undef if that particular THING hasn't been used yet,
+except in the case of scalars. *foo{SCALAR} returns a reference to an
+anonymous scalar if $foo hasn't been used yet. This might change in a
+future release.
+
+The use of *foo{IO} is the best way to pass bareword filehandles into or
+out of subroutines, or to store them in larger data structures.
splutter(*STDOUT{IO});
sub splutter {
@@ -224,9 +231,18 @@ or out of subroutines, or to store them in larger data structures.
return scalar <$fh>;
}
-The best way to do this used to be to use the entire *foo typeglob (or a
-reference to it), so you'll probably come across old code which does it
-that way.
+Beware, though, that you can't do this with a routine which is going to
+open the filehandle for you, because *HANDLE{IO} will be undef if HANDLE
+hasn't been used yet. Use \*HANDLE for that sort of thing instead.
+
+Using \*HANDLE (or *HANDLE) is another way to use and store non-bareword
+filehandles (before 5.002 it was the only way). The two methods are
+largely interchangeable, you can do
+
+ splutter(\*STDOUT);
+ $rec = get_rec(\*STDIN);
+
+with the above subroutine definitions.
=back
@@ -282,7 +298,7 @@ subscripted expressions:
Because of being able to omit the curlies for the simple case of C<$$x>,
people often make the mistake of viewing the dereferencing symbols as
proper operators, and wonder about their precedence. If they were,
-though, you could use parens instead of braces. That's not the case.
+though, you could use parentheses instead of braces. That's not the case.
Consider the difference below; case 0 is a short-hand version of case 1,
I<NOT> case 2:
@@ -348,7 +364,7 @@ reference is pointing to. See L<perlfunc>.
The bless() operator may be used to associate a reference with a package
functioning as an object class. See L<perlobj>.
-A typeglob may be dereferenced the same way a reference can, since
+A typeglob may be dereferenced the same way a reference can, because
the dereference syntax always indicates the kind of reference desired.
So C<${*foo}> and C<${\$foo}> both indicate the same scalar variable.
@@ -447,7 +463,7 @@ subscripting a hash. So now, instead of writing
$array{ "aaa" }{ "bbb" }{ "ccc" }
-you can just write
+you can write just
$array{ aaa }{ bbb }{ ccc }
@@ -464,7 +480,7 @@ makes it more than a bareword:
$array{ shift @_ }
The B<-w> switch will warn you if it interprets a reserved word as a string.
-But it will no longer warn you about using lowercase words, since the
+But it will no longer warn you about using lowercase words, because the
string is effectively quoted.
=head1 WARNING