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cpan/perlfaq - Update to version 5.20240218
5.20240218 2024-02-18 17:37:25Z
* add entry for "UTF-8 string" in perlglossary (PR#99, Felipe Gasper)
* update the bug tracker advice to de-emphasize rt.cpan.org (PR#107, brian d foy)
* plug CLDR::Number instead of Number::Format in perlfaq5 (PR#108, brian d foy)
* misc code sample fixes in perlfaq4 (PR#109, brian d foy)
* minor wording fixes in perlfaq5 (Karen Etheridge)
* fix assertion about Python and closures (PR#114, E. Choroba)
* improve the section on uniq perlfaq4 (PR#116, E. Choroba)
* remove mention of Perl 4 in perlfaq1 (PR#113, Joelle Maslak)
* document that smartmatch, given and when will be removed in Perl 5.42 (PR#115,
Philippe Bruhat (BooK))
This commit is contained in:
Karen Etheridge
parent
a1af65b9a8
commit
818effc8df
@ -907,8 +907,7 @@ our %Modules = (
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},
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'perlfaq' => {
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'DISTRIBUTION' => 'ETHER/perlfaq-5.20230812.tar.gz',
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'SYNCINFO' => 'jkeenan on Wed Aug 16 18:13:51 2023',
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'DISTRIBUTION' => 'ETHER/perlfaq-5.20240218.tar.gz',
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'FILES' => q[cpan/perlfaq],
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'EXCLUDED' => [ qr/^inc/, qr/^xt/, qr{^t/00-} ],
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},
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@ -2,6 +2,6 @@ use strict;
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use warnings;
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package perlfaq;
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our $VERSION = '5.20230812';
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our $VERSION = '5.20240218';
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1;
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@ -4,7 +4,7 @@ perlfaq - Frequently asked questions about Perl
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=head1 VERSION
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version 5.20230812
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version 5.20240218
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=head1 DESCRIPTION
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@ -88,10 +88,6 @@ Which version of Perl should I use?
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=item *
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What are Perl 4, Perl 5, or Raku (Perl 6)?
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=item *
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What is Raku (Perl 6)?
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=item *
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@ -720,7 +716,7 @@ How can I translate tildes (~) in a filename?
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=item *
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How come when I open a file read-write it wipes it out?
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When I open a file read-write, why does it wipe it out?
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=item *
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@ -1079,7 +1075,7 @@ How do I find out which operating system I'm running under?
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=item *
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How come exec() doesn't return?
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Why does exec() not return?
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=item *
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@ -4,7 +4,7 @@ perlfaq1 - General Questions About Perl
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=head1 VERSION
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version 5.20230812
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version 5.20240218
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=head1 DESCRIPTION
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@ -123,28 +123,6 @@ current stable release of Perl.
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=back
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=head2 What are Perl 4, Perl 5, or Raku (Perl 6)?
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In short, Perl 4 is the parent to both Perl 5 and Raku (formerly known as
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Perl 6). Perl 5 is the older sibling, and though they are different languages,
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someone who knows one will spot many similarities in the other.
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The number after Perl (i.e. the 5 after Perl 5) is the major release
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of the perl interpreter as well as the version of the language. Each
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major version has significant differences that earlier versions cannot
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support.
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The current major release of Perl is Perl 5, first released in
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1994. It can run scripts from the previous major release, Perl 4
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(March 1991), but has significant differences.
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Raku is a reinvention of Perl, a language in the same lineage but
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not compatible. The two are complementary, not mutually exclusive. Raku is
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not meant to replace Perl, and vice versa. See L</"What is Raku (Perl 6)?">
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below to find out more.
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See L<perlhist> for a history of Perl revisions.
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=head2 What is Raku (Perl 6)?
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Raku (formerly known as Perl 6) was I<originally> described as the community's
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@ -8,7 +8,7 @@ perlfaq2 - Obtaining and Learning about Perl
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=head1 VERSION
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version 5.20230812
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version 5.20240218
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=head1 DESCRIPTION
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@ -221,25 +221,46 @@ First, ensure that you've found an actual bug. Second, ensure you've
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found an actual bug.
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If you've found a bug with the perl interpreter or one of the modules
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in the standard library (those that come with Perl), you can submit a
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in the standard library (those that come with Perl), submit a
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bug report to the GitHub issue tracker at
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L<https://github.com/Perl/perl5/issues>.
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To determine if a module came with your version of Perl, you can
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install and use the L<Module::CoreList> module. It has the information
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about the modules (with their versions) included with each release
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of Perl.
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install and use L<Module::CoreList>. It knows the modules (with their
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versions) included with each release of Perl:
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Every CPAN module has a bug tracker set up in RT, L<http://rt.cpan.org>.
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You can submit bugs to RT either through its web interface or by
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email. To email a bug report, send it to
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bug-E<lt>distribution-nameE<gt>@rt.cpan.org . For example, if you
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wanted to report a bug in L<Business::ISBN>, you could send a message to
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bug-Business-ISBN@rt.cpan.org .
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$ corelist File::Copy
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Data for 2023-07-02
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File::Copy was first released with perl 5.002
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Some modules might have special reporting requirements, such as a
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GitHub or Google Code tracking system, so you should check the
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module documentation too.
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$ corelist Business::ISBN
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Data for 2023-07-02
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Business::ISBN was not in CORE (or so I think)
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If the module does not come with Perl, report its issues
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using the tool that the particular module author decided to use, such as
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a GitHub or Google Code. The quickest way may be to check the MetaCPAN
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page for the module (for example,
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L<https://metacpan.org/pod/Business::ISBN>), which shows the denoted
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bugtracker in the left sidebar as the "Issues" link.
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Also check the module's documentation, F<README>, the build files
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(F<Makefile.PL> or C<Build.PL>), or F<META.{json,yml}> files. Although
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many module authors follow the same pattern, some have their own way.
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Use the directions you find.
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Sometimes the module author does not declare a bugtracker. For a long
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time, everyone assumed that the CPAN Request Tracker
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(L<https://rt.cpan.org>) was the bugtracker since every distribution had
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an RT queue generated automatically. In somes cases, the author might
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use CPAN RT. They also might have not declared a different
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bugtracker but don't use CPAN RT.
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Submit bugs to RT either through its web interface,
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L<https://rt.cpan.org>, or by email. Send email to I<<
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bug-E<lt>distribution-nameE<gt>@rt.cpan.org >>. For example, if you
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wanted to report a bug in the example module L<Foo::Bar>, you could send
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a message to I<bug-Foo-Bar@rt.cpan.org>.
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=head1 AUTHOR AND COPYRIGHT
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@ -4,7 +4,7 @@ perlfaq3 - Programming Tools
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=head1 VERSION
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version 5.20230812
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version 5.20240218
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=head1 DESCRIPTION
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@ -4,7 +4,7 @@ perlfaq4 - Data Manipulation
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=head1 VERSION
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version 5.20230812
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version 5.20240218
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=head1 DESCRIPTION
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@ -886,39 +886,57 @@ X<Text::Autoformat> X<capitalize> X<case, title> X<case, sentence>
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(contributed by brian d foy)
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Damian Conway's L<Text::Autoformat> handles all of the thinking
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for you.
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for you:
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use Text::Autoformat;
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my $x = "Dr. Strangelove or: How I Learned to Stop ".
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"Worrying and Love the Bomb";
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my $s = "Going to the desert with a camel";
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print $x, "\n";
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printf "%-10s %s\n", "original:", $s;
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for my $style (qw( sentence title highlight )) {
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print autoformat($x, { case => $style }), "\n";
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printf "%-10s %s\n",
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"$style:",
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autoformat($s, { case => $style }) =~ s/\R+\z//r;
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}
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How do you want to capitalize those words?
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Each style has a different idea of what if should do with small words:
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FRED AND BARNEY'S LODGE # all uppercase
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Fred And Barney's Lodge # title case
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Fred and Barney's Lodge # highlight case
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original: Going to the desert with a camel
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sentence: Going to the desert with a camel
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title: Going To The Desert With A Camel
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highlight: Going to the Desert with a Camel
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It's not as easy a problem as it looks. How many words do you think
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are in there? Wait for it... wait for it.... If you answered 5
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you're right. Perl words are groups of C<\w+>, but that's not what
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you want to capitalize. How is Perl supposed to know not to capitalize
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that C<s> after the apostrophe? You could try a regular expression:
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Trying this yourself in a simple regex has more than a few pitfalls.
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Perl "words" are groups of C<\w+>, but that's not what you want to
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capitalize. Some of those characters aren't even letters. What if you
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used a word boundary, C<\b>?
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$string =~ s/ (
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(^\w) #at the beginning of the line
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| # or
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(\s\w) #preceded by whitespace
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)
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/\U$1/xg;
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my $string = "A camel's journey";
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$string =~ s/\b(\w)/\U$1/g; # A Camel'S Journey
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How is Perl supposed to know not to capitalize that C<s>? You could work
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harder to look for preceding whitespace or the beginning of the string:
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$string =~ s/( (?:^|\s) \w ) /\U$1/xg; # A Camel's Journey
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Or maybe you match the entire group, lowercase it all (C<L>), then
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uppercase the first letter (C<\u>):
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$string =~ s/([\w']+)/\u\L$1/g;
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Now, what if you don't want to capitalize that "and"? Just use
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Each of these have their annoying edge cases. Perl v5.22 added fancier
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Unicode word and sentence boundaries to fix this sort of problem. The
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C<\b{wb}> word boundary ignores some things that it doesn't think start
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or end "human" words:
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use v5.22;
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my $string = "A camel's journey";
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$string =~ s/\b{wb}(\w)/\U$1/g; # A Camel's Journey
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The details are in Unicode Technical Report #29
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(L<https://unicode.org/reports/tr29/>), and you should make sure that
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its idea of a word boundary corresponds to yours.
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Now, what if you don't want to capitalize that "and" or "the"? Just use
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L<Text::Autoformat> and get on with the next problem. :)
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=head2 How can I split a [character]-delimited string except when inside [character]?
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@ -1459,18 +1477,18 @@ elements.
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my @unique = keys %hash;
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If you want to use a module, try the C<uniq> function from
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L<List::MoreUtils>. In list context it returns the unique elements,
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L<List::Util>. In list context it returns the unique elements,
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preserving their order in the list. In scalar context, it returns the
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number of unique elements.
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use List::MoreUtils qw(uniq);
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use List::Util qw(uniq);
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my @unique = uniq( 1, 2, 3, 4, 4, 5, 6, 5, 7 ); # 1,2,3,4,5,6,7
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my $unique = uniq( 1, 2, 3, 4, 4, 5, 6, 5, 7 ); # 7
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my @unique = uniq( 1, 2, 3, 4, 4, 5, 6, 5, 8 ); # 1,2,3,4,5,6,8
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my $unique = uniq( 1, 2, 3, 4, 4, 5, 6, 5, 8 ); # 7
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You can also go through each element and skip the ones you've seen
|
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before. Use a hash to keep track. The first time the loop sees an
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element, that element has no key in C<%Seen>. The C<next> statement
|
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element, that element has no key in C<%seen>. The C<next> statement
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creates the key and immediately uses its value, which is C<undef>, so
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the loop continues to the C<push> and increments the value for that
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key. The next time the loop sees that same element, its key exists in
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@ -4,7 +4,7 @@ perlfaq5 - Files and Formats
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=head1 VERSION
|
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|
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version 5.20230812
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version 5.20240218
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=head1 DESCRIPTION
|
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@ -708,12 +708,38 @@ X<number, commify>
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(contributed by brian d foy and Benjamin Goldberg)
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You can use L<Number::Format> to separate places in a number.
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It handles locale information for those of you who want to insert
|
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full stops instead (or anything else that they want to use,
|
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really).
|
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The L<CLDR::Number> module (the Unicode Common Locale Data Repository)
|
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knows how to format numbers based on a locale to use its
|
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digit grouping and separator:
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|
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This subroutine will add commas to your number:
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use CLDR::Number;
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my $number = 1234567890;
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foreach my $locale ( qw(en-US de-DE en-IN) ) {
|
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my $cldr = CLDR::Number->new( locale => $locale );
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my $decimal = $cldr->decimal_formatter;
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printf "%-5s %s\n", $locale, $decimal->format( $number );
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}
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The output shows the same number formatted according to each locale's
|
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rules. The bare C<en> uses commas between groups of three, the C<de>
|
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uses dots and groups of three, and the C<en-IN> uses the 3:2:2 rule with
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commas:
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|
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en-US 1,234,567,890
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de-DE 1.234.567.890
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en-IN 1,23,45,67,890
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L<CLDR::Number> has many more advanced features to handle just about
|
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anything that you might want. Olaf Alders' article "Stop Writing Your Own
|
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Commify Functions" has more examples
|
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(L<https://www.olafalders.com/2015/09/04/stop-writing-your-own-commify-
|
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functions/>).
|
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|
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If you know exactly what you want, a simple subroutine might suffice.
|
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This example will add separators to your number between groups of three
|
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digits (or whatever grouping). This uses groups of three and a comma:
|
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|
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sub commify {
|
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local $_ = shift;
|
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@ -721,7 +747,7 @@ This subroutine will add commas to your number:
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return $_;
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}
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|
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This regex from Benjamin Goldberg will add commas to numbers:
|
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This regex from Benjamin Goldberg does the same thing without the loop:
|
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|
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s/(^[-+]?\d+?(?=(?>(?:\d{3})+)(?!\d))|\G\d{3}(?=\d))/$1,/g;
|
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|
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@ -762,7 +788,7 @@ Within Perl, you may use this directly:
|
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: ( $ENV{HOME} || $ENV{LOGDIR} )
|
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}ex;
|
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|
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=head2 How come when I open a file read-write it wipes it out?
|
||||
=head2 When I open a file read-write, why does it wipe it out?
|
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X<clobber> X<read-write> X<clobbering> X<truncate> X<truncating>
|
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|
||||
Because you're using something like this, which truncates the file
|
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@ -1494,7 +1520,7 @@ array in double quotes. You can send it to print without them:
|
||||
(contributed by brian d foy)
|
||||
|
||||
The L<File::Find> module, which comes with Perl, does all of the hard
|
||||
work to traverse a directory structure. It comes with Perl. You simply
|
||||
work to traverse a directory structure. You simply
|
||||
call the C<find> subroutine with a callback subroutine and the
|
||||
directories you want to traverse:
|
||||
|
||||
|
||||
@ -4,7 +4,7 @@ perlfaq6 - Regular Expressions
|
||||
|
||||
=head1 VERSION
|
||||
|
||||
version 5.20230812
|
||||
version 5.20240218
|
||||
|
||||
=head1 DESCRIPTION
|
||||
|
||||
|
||||
@ -4,7 +4,7 @@ perlfaq7 - General Perl Language Issues
|
||||
|
||||
=head1 VERSION
|
||||
|
||||
version 5.20230812
|
||||
version 5.20240218
|
||||
|
||||
=head1 DESCRIPTION
|
||||
|
||||
@ -266,10 +266,10 @@ binding).
|
||||
Closures are most often used in programming languages where you can
|
||||
have the return value of a function be itself a function, as you can
|
||||
in Perl. Note that some languages provide anonymous functions but are
|
||||
not capable of providing proper closures: the Python language, for
|
||||
example. For more information on closures, check out any textbook on
|
||||
functional programming. Scheme is a language that not only supports
|
||||
but encourages closures.
|
||||
not capable of providing proper closures: for example Python 2. For
|
||||
more information on closures, check out any textbook on functional
|
||||
programming. Scheme is a language that not only supports but
|
||||
encourages closures.
|
||||
|
||||
Here's a classic non-closure function-generating function:
|
||||
|
||||
@ -696,7 +696,7 @@ details, see L<perlsub>.
|
||||
=head2 How do I create a switch or case statement?
|
||||
|
||||
There is a given/when statement in Perl, but it is experimental and
|
||||
likely to change in future. See L<perlsyn> for more details.
|
||||
will be removed in Perl 5.42. See L<perlsyn> for more details.
|
||||
|
||||
The general answer is to use a CPAN module such as L<Switch::Plain>:
|
||||
|
||||
|
||||
@ -4,7 +4,7 @@ perlfaq8 - System Interaction
|
||||
|
||||
=head1 VERSION
|
||||
|
||||
version 5.20230812
|
||||
version 5.20240218
|
||||
|
||||
=head1 DESCRIPTION
|
||||
|
||||
@ -23,7 +23,7 @@ The C<$^O> variable (C<$OSNAME> if you use C<English>) contains an
|
||||
indication of the name of the operating system (not its release
|
||||
number) that your perl binary was built for.
|
||||
|
||||
=head2 How come exec() doesn't return?
|
||||
=head2 Why does exec() not return?
|
||||
X<exec> X<system> X<fork> X<open> X<pipe>
|
||||
|
||||
(contributed by brian d foy)
|
||||
|
||||
@ -4,7 +4,7 @@ perlfaq9 - Web, Email and Networking
|
||||
|
||||
=head1 VERSION
|
||||
|
||||
version 5.20230812
|
||||
version 5.20240218
|
||||
|
||||
=head1 DESCRIPTION
|
||||
|
||||
|
||||
@ -7,7 +7,7 @@ perlglossary - Perl Glossary
|
||||
|
||||
=head1 VERSION
|
||||
|
||||
version 5.20230812
|
||||
version 5.20240218
|
||||
|
||||
=head1 DESCRIPTION
|
||||
|
||||
@ -3298,6 +3298,9 @@ called a “case structure”, named after the similar Pascal construct. Most
|
||||
switch statements in Perl are spelled C<given>. See “The C<given>
|
||||
statement” in Camel chapter 4, “Statements and Declarations”.
|
||||
|
||||
The C<given>, C<when> keywords and the smartmatch (C<~~>) operator will
|
||||
be removed in Perl 5.42.
|
||||
|
||||
=item symbol
|
||||
|
||||
Generally, X<symbols>X<symbols>any B<token> or B<metasymbol>. Often used
|
||||
@ -3613,6 +3616,15 @@ characters with the General Category of Uppercase Letter, but any character
|
||||
with the Uppercase property, including some Letter Numbers and Symbols. Not
|
||||
to be confused with B<titlecase>.
|
||||
|
||||
=item UTF-8 string
|
||||
|
||||
A L</string> whose ordinals represent a valid sequence of UTF-8 bytes.
|
||||
Sometimes called a "UTF-8 encoded string".
|
||||
|
||||
(B<IMPORTANT:> This is unrelated to Perl’s internal
|
||||
L<“UTF8 flag”|perlunifaq/What is "the UTF8 flag"?>, which only Perl itself
|
||||
should usually care about. UTF-8 strings may have that flag set or unset.)
|
||||
|
||||
=back
|
||||
|
||||
=head2 V
|
||||
|
||||
Loading…
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Reference in New Issue
Block a user