[PATCH] Document for(;;) and while() in perlsyn

[p5pRT]

Migrated from rt.perl.org#122015 (status was 'resolved')

Searchable as RT122015$

[p5pRT]

From [email protected]

for(;;) and while() do not appear to be documented in core; attached
is a patch to perlsyn to at least reference them somewhere, for
discussion.

Summary of my perl5 (revision 5 version 20 subversion 0) configuration​:
  Commit id​: d7d4ece
  Platform​:
  osname=linux, osvers=3.13.0-24-generic, archname=x86_64-linux
  uname='linux pmubuntu 3.13.0-24-generic #46-ubuntu smp thu apr 10
19​:11​:08 utc 2014 x86_64 x86_64 x86_64 gnulinux '
  config_args='-DDEBUGGING -des'
  hint=recommended, useposix=true, d_sigaction=define
  useithreads=undef, usemultiplicity=undef
  use64bitint=define, use64bitall=define, uselongdouble=undef
  usemymalloc=n, bincompat5005=undef
  Compiler​:
  cc='cc', ccflags ='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe
-fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64',
  optimize='-O2 -g',
  cppflags='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe
-fstack-protector -I/usr/local/include'
  ccversion='', gccversion='4.8.2', gccosandvers=''
  intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
  ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
  alignbytes=8, prototype=define
  Linker and Libraries​:
  ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
  libpth=/usr/local/lib
/usr/lib/gcc/x86_64-linux-gnu/4.8/include-fixed
/usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu
/lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
  libs=-lnsl -ldl -lm -lcrypt -lutil -lc
  perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
  libc=libc-2.19.so, so=so, useshrplib=false, libperl=libperl.a
  gnulibc_version='2.19'
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
  cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib
-fstack-protector'

Characteristics of this binary (from libperl)​:
  Compile-time options​: DEBUGGING HAS_TIMES PERLIO_LAYERS
  PERL_DONT_CREATE_GVSV
  PERL_HASH_FUNC_ONE_AT_A_TIME_HARD PERL_MALLOC_WRAP
  PERL_NEW_COPY_ON_WRITE PERL_PRESERVE_IVUV
  USE_64_BIT_ALL USE_64_BIT_INT USE_LARGE_FILES
  USE_LOCALE USE_LOCALE_COLLATE USE_LOCALE_CTYPE
  USE_LOCALE_NUMERIC USE_PERLIO USE_PERL_ATOF
  Built under linux
  Compiled at May 29 2014 00​:05​:39
  @​INC​:
  /usr/local/lib/perl5/site_perl/5.20.0/x86_64-linux
  /usr/local/lib/perl5/site_perl/5.20.0
  /usr/local/lib/perl5/5.20.0/x86_64-linux
  /usr/local/lib/perl5/5.20.0
  /usr/local/lib/perl5/site_perl/5.19.9
  /usr/local/lib/perl5/site_perl/5.19.5
  /usr/local/lib/perl5/site_perl/5.18.1
  /usr/local/lib/perl5/site_perl
  .

[p5pRT]

From [email protected]

0001-Document-empty-conditional-in-for-while.patch

From 62b13428938b1bde786bf346daacb1b5069dd610 Mon Sep 17 00:00:00 2001
From: Peter Martini <[email protected]>
Date: Mon, 2 Jun 2014 07:16:59 -0400
Subject: [PATCH] Document empty conditional in for/while

An empty conditional in both for and while has been treated
as true since perl 1.0.  This has a clear analogue in C/C++
in the case of for(;;), but while() is not legal C and should
be documented.
---
 pod/perlsyn.pod | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/pod/perlsyn.pod b/pod/perlsyn.pod
index 244372c..cea4d50 100644
--- a/pod/perlsyn.pod
+++ b/pod/perlsyn.pod
@@ -429,6 +429,21 @@ those variables is exactly the C<for> loop (the body of the loop
 and the control sections).
 X<my>
 
+As a special case, if the test in the C<for> loop (or the corresponding
+C<while> loop) is empty, it is treated as true.  That is, both
+
+    for (;;) {
+	...
+    }
+
+and
+
+    while () {
+	...
+    }
+
+are treated as infinite loops.
+
 Besides the normal array index looping, C<for> can lend itself
 to many other interesting applications.  Here's one that avoids the
 problem you get into if you explicitly test for end-of-file on
-- 
1.9.1

[p5pRT]

From @jkeenan

On Mon Jun 02 04​:23​:46 2014, pcm wrote​:

for(;;) and while() do not appear to be documented in core; attached
is a patch to perlsyn to at least reference them somewhere, for
discussion.

Seems reasonable to me. Any objection to applying?

Thank you very much.
Jim Keenan

[p5pRT]

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

[p5pRT]

From @khwilliamson

On Mon Jun 02 13​:40​:32 2014, jkeenan wrote​:

On Mon Jun 02 04​:23​:46 2014, pcm wrote​:

for(;;) and while() do not appear to be documented in core; attached
is a patch to perlsyn to at least reference them somewhere, for
discussion.

Seems reasonable to me. Any objection to applying?

Thank you very much.
Jim Keenan

+1 to applying
--
Karl Williamson

[p5pRT]

From @jkeenan

Pushed to blead in commit 62bd8e4. Resolving ticket.

Thank you very much.
Jim Keenan

[p5pRT]

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