common-sense/sense.pm

=head1 NAME

common::sense - save a tree AND a kitten, use common::sense!

=head1 SYNOPSIS

 use common::sense;

 # roughly the same as, with much lower memory usage:
 #
 # use strict qw(vars subs);
 # use feature qw(say state switch);
 # no warnings;

=head1 DESCRIPTION

This module implements some sane defaults for Perl programs, as defined by
two typical (or not so typical - use your common sense) specimens of
Perl coders.

=over 4

=item no warnings

Ah, the dreaded warnings. Even worse, the horribly dreaded C<-w>
switch: Even though we don't care if other people use warnings (and
certainly there are useful ones), a lot of warnings simply go against the
spirit of Perl.

Most prominently, the warnings related to C<undef>. There is nothing wrong
with C<undef>: it has well-defined semantics, it is useful, and spitting
out warnings you never asked for is just evil.

So every module needs C<no warnings> to avoid somebody accidentally using
C<-w> and forcing his bad standards on our code. No will do. Really, the
C<-w> switch should only enable wanrings for the main program.

Funnily enough, L<perllexwarn> explicitly mentions C<-w> (and not in a
favourable way), but standard utilities, such as L<prove>, or MakeMaker
when running C<make test> enable them blindly.

=item use strict qw(subs vars)

Using C<use strict> is definitely common sense, but C<use strict
'refs'> definitely overshoots its usefulness. After almost two
decades of Perl hacking, we decided that it does more harm than being
useful. Specifically, constructs like these:

   @{ $var->[0] }

Must be written like this (or similarly), when C<use strict 'refs'> is in
scope, and C<$var> can legally be C<undef>:

   @{ $var->[0] || [] }

This is annoying, and doesn't shield against obvious mistakes such as
using C<"">, so one would even have to write (at least for the time
being):

   @{ defined $var->[0] ? $var->[0] :  [] }

... which nobody with a bit of common sense would consider
writing.

Curiously enough, sometimes perl is not so strict, as this works even with
C<use strict> in scope:

   for (@{ $var->[0] }) { ...

If that isn't hipocrasy! And all that from a mere program!

=item use feature qw(say state given)

We found it annoying that we always have to enable extra features. If
something breaks because it didn't anticipate future changes, so be
it. 5.10 broke almost all our XS modules and nobody cared either (or at
leats I know of nobody who really complained about gratitious changes - as
opposed to bugs).

Few modules that are not actively maintained work with newer versions of
Perl, regardless of use feature or not, so a new major perl release means
changes to many modules - new keywords are just the tip of the iceberg.

If your code isn't alive, it's dead, jim - be an active maintainer.

=item mucho reduced memory usage

Just using all those pragmas mentioned in the SYNOPSIS together wastes
<blink>I<< B<776> kilobytes >></blink> of precious memory in my perl, for
I<every single perl process using our code>, which on our machines, is a
lot. In comparison, this module only uses I<< B<four> >> kilobytes (I even
had to write it out so it looks like more) of memory on the same platform.

The money/time/effort/electricity invested in these gigabytes (probably
petabytes globally!) of wasted memory could easily save 42 trees, and a
kitten!

Unfortunately, until everybods applies more common sense, there will still
often be modules that pull in the monster pragmas. But one can hope...

=cut

package common::sense;

our $VERSION = '1.0';

sub import {
   # no warnings
   ${^WARNING_BITS} ^= ${^WARNING_BITS};

   # use strict vars subs
   $^H |= 0x00000600;

   # use feature
   $^H{feature_switch} =
   $^H{feature_say}    =
   $^H{feature_state}  = 1;
}

1;

=back

=head1 THERE IS NO 'no common::sense'!!!! !!!! !!

This module doesn't offer an unimport. First of all, it wastes even more
memory, second, and more importantly, who with even a bit of common sense
would want no common sense?

=head1 STABILITY AND FUTURE VERSIONS

Future versions might change just about everything in this module. We
might test our modules and upload new ones working with newer versions of
this module, and leave you standing in the rain because we didn't tell
you.

Most likely, we will pick a few useful warnings, instead of just disabling
all of them. And maybe we will load some nifty modules that try to emulate
C<say> or so with perls older than 5.10 (this module, of course, should
work with older perl versions - supporting 5.8 for example is just common
sense at this time. Maybe not in the future, but of course you can trust
our common sense to be consistent with, uhm, our opinion).

=head1 WHAT OTHER PEOPLE HAD TO SAY ABOUT THIS MODULE

apeiron

   "... wow"
   "I hope common::sense is a joke."

crab

   "i wonder how it would be if joerg schilling wrote perl modules."

H.Merijn Brand

   "Just one more reason to drop JSON::XS from my distribution list"

Pista Palo

   "Something in short supply these days..."

Steffen Schwigon

   "This module is quite for sure *not* just a repetition of all the other
   'use strict, use warnings'-approaches, and it's also not the opposite.
   [...] And for its chosen middle-way it's also not the worst name ever.
   And everything is documented."

BKB

   "[Deleted - thanks to Steffen Schwigon for pointing out this review was
   in error.]"

Somni

   "the arrogance of the guy"
   "I swear he tacked somenoe else's name onto the module
   just so he could use the royal 'we' in the documentation"

dngor

   "Heh.  '"<elmex at ta-sa.org>"'  The quotes are semantic
   distancing from that e-mail address."

Jerad Pierce

   "Awful name (not a proper pragma), and the SYNOPSIS doesn't tell you
   anything either. Nor is it clear what features have to do with "common
   sense" or discipline."

acme

   "THERE IS NO 'no common::sense'!!!! !!!! !!"

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

 Robin Redeker, "<elmex at ta-sa.org>".

=cut

Revision:	1.11
Committed:	Sat Aug 22 20:21:29 2009 UTC (14 years, 10 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_0
Changes since 1.10:	+53 -41 lines
Log Message:	1.0
#	Content
1	=head1 NAME
2
3	common::sense - save a tree AND a kitten, use common::sense!
4
5	=head1 SYNOPSIS
6
7	use common::sense;
8
9	# roughly the same as, with much lower memory usage:
10	#
11	# use strict qw(vars subs);
12	# use feature qw(say state switch);
13	# no warnings;
14
15	=head1 DESCRIPTION
16
17	This module implements some sane defaults for Perl programs, as defined by
18	two typical (or not so typical - use your common sense) specimens of
19	Perl coders.
20
21	=over 4
22
23	=item no warnings
24
25	Ah, the dreaded warnings. Even worse, the horribly dreaded C<-w>
26	switch: Even though we don't care if other people use warnings (and
27	certainly there are useful ones), a lot of warnings simply go against the
28	spirit of Perl.
29
30	Most prominently, the warnings related to C<undef>. There is nothing wrong
31	with C<undef>: it has well-defined semantics, it is useful, and spitting
32	out warnings you never asked for is just evil.
33
34	So every module needs C<no warnings> to avoid somebody accidentally using
35	C<-w> and forcing his bad standards on our code. No will do. Really, the
36	C<-w> switch should only enable wanrings for the main program.
37
38	Funnily enough, L<perllexwarn> explicitly mentions C<-w> (and not in a
39	favourable way), but standard utilities, such as L<prove>, or MakeMaker
40	when running C<make test> enable them blindly.
41
42	=item use strict qw(subs vars)
43
44	Using C<use strict> is definitely common sense, but C<use strict
45	'refs'> definitely overshoots its usefulness. After almost two
46	decades of Perl hacking, we decided that it does more harm than being
47	useful. Specifically, constructs like these:
48
49	@{ $var->[0] }
50
51	Must be written like this (or similarly), when C<use strict 'refs'> is in
52	scope, and C<$var> can legally be C<undef>:
53
54	@{ $var->[0] \|\| [] }
55
56	This is annoying, and doesn't shield against obvious mistakes such as
57	using C<"">, so one would even have to write (at least for the time
58	being):
59
60	@{ defined $var->[0] ? $var->[0] : [] }
61
62	... which nobody with a bit of common sense would consider
63	writing.
64
65	Curiously enough, sometimes perl is not so strict, as this works even with
66	C<use strict> in scope:
67
68	for (@{ $var->[0] }) { ...
69
70	If that isn't hipocrasy! And all that from a mere program!
71
72	=item use feature qw(say state given)
73
74	We found it annoying that we always have to enable extra features. If
75	something breaks because it didn't anticipate future changes, so be
76	it. 5.10 broke almost all our XS modules and nobody cared either (or at
77	leats I know of nobody who really complained about gratitious changes - as
78	opposed to bugs).
79
80	Few modules that are not actively maintained work with newer versions of
81	Perl, regardless of use feature or not, so a new major perl release means
82	changes to many modules - new keywords are just the tip of the iceberg.
83
84	If your code isn't alive, it's dead, jim - be an active maintainer.
85
86	=item mucho reduced memory usage
87
88	Just using all those pragmas mentioned in the SYNOPSIS together wastes
89	<blink>I<< B<776> kilobytes >></blink> of precious memory in my perl, for
90	I<every single perl process using our code>, which on our machines, is a
91	lot. In comparison, this module only uses I<< B<four> >> kilobytes (I even
92	had to write it out so it looks like more) of memory on the same platform.
93
94	The money/time/effort/electricity invested in these gigabytes (probably
95	petabytes globally!) of wasted memory could easily save 42 trees, and a
96	kitten!
97
98	Unfortunately, until everybods applies more common sense, there will still
99	often be modules that pull in the monster pragmas. But one can hope...
100
101	=cut
102
103	package common::sense;
104
105	our $VERSION = '1.0';
106
107	sub import {
108	# no warnings
109	${^WARNING_BITS} ^= ${^WARNING_BITS};
110
111	# use strict vars subs
112	$^H \|= 0x00000600;
113
114	# use feature
115	$^H{feature_switch} =
116	$^H{feature_say} =
117	$^H{feature_state} = 1;
118	}
119
120	1;
121
122	=back
123
124	=head1 THERE IS NO 'no common::sense'!!!! !!!! !!
125
126	This module doesn't offer an unimport. First of all, it wastes even more
127	memory, second, and more importantly, who with even a bit of common sense
128	would want no common sense?
129
130	=head1 STABILITY AND FUTURE VERSIONS
131
132	Future versions might change just about everything in this module. We
133	might test our modules and upload new ones working with newer versions of
134	this module, and leave you standing in the rain because we didn't tell
135	you.
136
137	Most likely, we will pick a few useful warnings, instead of just disabling
138	all of them. And maybe we will load some nifty modules that try to emulate
139	C<say> or so with perls older than 5.10 (this module, of course, should
140	work with older perl versions - supporting 5.8 for example is just common
141	sense at this time. Maybe not in the future, but of course you can trust
142	our common sense to be consistent with, uhm, our opinion).
143
144	=head1 WHAT OTHER PEOPLE HAD TO SAY ABOUT THIS MODULE
145
146	apeiron
147
148	"... wow"
149	"I hope common::sense is a joke."
150
151	crab
152
153	"i wonder how it would be if joerg schilling wrote perl modules."
154
155	H.Merijn Brand
156
157	"Just one more reason to drop JSON::XS from my distribution list"
158
159	Pista Palo
160
161	"Something in short supply these days..."
162
163	Steffen Schwigon
164
165	"This module is quite for sure not just a repetition of all the other
166	'use strict, use warnings'-approaches, and it's also not the opposite.
167	[...] And for its chosen middle-way it's also not the worst name ever.
168	And everything is documented."
169
170	BKB
171
172	"[Deleted - thanks to Steffen Schwigon for pointing out this review was
173	in error.]"
174
175	Somni
176
177	"the arrogance of the guy"
178	"I swear he tacked somenoe else's name onto the module
179	just so he could use the royal 'we' in the documentation"
180
181	dngor
182
183	"Heh. '"<elmex at ta-sa.org>"' The quotes are semantic
184	distancing from that e-mail address."
185
186	Jerad Pierce
187
188	"Awful name (not a proper pragma), and the SYNOPSIS doesn't tell you
189	anything either. Nor is it clear what features have to do with "common
190	sense" or discipline."
191
192	acme
193
194	"THERE IS NO 'no common::sense'!!!! !!!! !!"
195
196	=head1 AUTHOR
197
198	Marc Lehmann <schmorp@schmorp.de>
199	http://home.schmorp.de/
200
201	Robin Redeker, "<elmex at ta-sa.org>".
202
203	=cut
204