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

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.

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 it's 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:

   @{ 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 isnt 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 - and few
modules that are no longer maintained work with newer versions of Perl,
regardless of use feature.

If your code isn't alive, it's dead, jim.

=item much less memory

Just using all those pragmas together waste <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!

=cut

package common::sense;

our $VERSION = '0.04';

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).


=head1 WHAT OTHER PEOPLE HAVE TO SAY ABOUT THIS MODULE

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'!!!! !!!! !!"

crab

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

=head1 AUTHOR

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

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


=cut

Revision:	1.7
Committed:	Sun Aug 2 08:29:46 2009 UTC (14 years, 9 months ago) by root
Branch:	MAIN
CVS Tags:	rel-0_04
Changes since 1.6:	+45 -1 lines
Log Message:	0.04
#	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	The dreaded warnings. Even worse, the horribly dreaded C<-w> switch. Even
26	though we don't care if other people use warnings (and certainly there are
27	useful ones), a lot of warnings simply go against the spirit of Perl, most
28	prominently, the warnings related to C<undef>. There is nothing wrong with
29	C<undef>: it has well-defined semantics, it is useful, and spitting out
30	warnings you never asked for is just evil.
31
32	So every module needs C<no warnings> to avoid somebody accidentally using
33	C<-w> and forcing his bad standards on our code. No will do.
34
35	Funnily enough, L<perllexwarn> explicitly mentions C<-w> (and not in a
36	favourable way), but standard utilities, such as L<prove>, or MakeMaker
37	when running C<make test> enable them blindly.
38
39	=item use strict qw(subs vars)
40
41	Using C<use strict> is definitely common sense, but C<use strict
42	'refs'> definitely overshoots it's usefulness. After almost two
43	decades of Perl hacking, we decided that it does more harm than being
44	useful. Specifically, constructs like these:
45
46	@{ $var->[0] }
47
48	Must be written like this (or similarly), when C<use strict 'refs'> is in
49	scope, and C<$var> can legally be C<undef>:
50
51	@{ $var->[0] \|\| [] }
52
53	This is annoying, and doesn't shield against obvious mistakes such as
54	using C<"">, so one would even have to write:
55
56	@{ defined $var->[0] ? $var->[0] : [] }
57
58	... which nobody with a bit of common sense would consider
59	writing. Curiously enough, sometimes, perl is not so strict, as this works
60	even with C<use strict> in scope:
61
62	for (@{ $var->[0] }) { ...
63
64	If that isnt hipocrasy! And all that from a mere program!
65
66	=item use feature qw(say state given)
67
68	We found it annoying that we always have to enable extra features. If
69	something breaks because it didn't anticipate future changes, so be
70	it. 5.10 broke almost all our XS modules and nobody cared either - and few
71	modules that are no longer maintained work with newer versions of Perl,
72	regardless of use feature.
73
74	If your code isn't alive, it's dead, jim.
75
76	=item much less memory
77
78	Just using all those pragmas together waste <blink>I<< B<776> kilobytes
79	>></blink> of precious memory in my perl, for I<every single perl process
80	using our code>, which on our machines, is a lot. In comparison, this
81	module only uses I<< B<four> >> kilobytes (I even had to write it out so
82	it looks like more) of memory on the same platform.
83
84	The money/time/effort/electricity invested in these gigabytes (probably
85	petabytes globally!) of wasted memory could easily save 42 trees, and a
86	kitten!
87
88	=cut
89
90	package common::sense;
91
92	our $VERSION = '0.04';
93
94	sub import {
95	# no warnings
96	${^WARNING_BITS} ^= ${^WARNING_BITS};
97
98	# use strict vars subs
99	$^H \|= 0x00000600;
100
101	# use feature
102	$^H{feature_switch} =
103	$^H{feature_say} =
104	$^H{feature_state} = 1;
105	}
106
107	1;
108
109	=back
110
111	=head1 THERE IS NO 'no common::sense'!!!! !!!! !!
112
113	This module doesn't offer an unimport. First of all, it wastes even more
114	memory, second, and more importantly, who with even a bit of common sense
115	would want no common sense?
116
117	=head1 STABILITY AND FUTURE VERSIONS
118
119	Future versions might change just about everything in this module. We
120	might test our modules and upload new ones working with newer versions of
121	this module, and leave you standing in the rain because we didn't tell
122	you.
123
124	Most likely, we will pick a few useful warnings, instead of just disabling
125	all of them. And maybe we will load some nifty modules that try to emulate
126	C<say> or so with perls older than 5.10 (this module, of course, should
127	work with older perl versions - supporting 5.8 for example is just common
128	sense at this time. Maybe not in the future, but of course you can trust
129	our common sense).
130
131
132	=head1 WHAT OTHER PEOPLE HAVE TO SAY ABOUT THIS MODULE
133
134	Pista Palo
135
136	"Something in short supply these days..."
137
138	Steffen Schwigon
139
140	"This module is quite for sure not just a repetition of all the other
141	'use strict, use warnings'-approaches, and it's also not the opposite.
142	[...] And for its chosen middle-way it's also not the worst name ever.
143	And everything is documented."
144
145	BKB
146
147	"[Deleted - thanks to Steffen Schwigon for pointing out this review was
148	in error.]"
149
150	Somni
151
152	"the arrogance of the guy"
153	"I swear he tacked somenoe else's name onto the module
154	just so he could use the royal 'we' in the documentation"
155
156	dngor
157
158	"Heh. '"<elmex at ta-sa.org>"' The quotes are semantic
159	distancing from that e-mail address."
160
161	Jerad Pierce
162
163	"Awful name (not a proper pragma), and the SYNOPSIS doesn't tell you
164	anything either. Nor is it clear what features have to do with "common
165	sense" or discipline."
166
167	acme
168
169	"THERE IS NO 'no common::sense'!!!! !!!! !!"
170
171	crab
172
173	"i wonder how it would be if joerg schilling wrote perl modules."
174
175	=head1 AUTHOR
176
177	Marc Lehmann <schmorp@schmorp.de>
178	http://home.schmorp.de/
179
180	Robin Redeker, "<elmex at ta-sa.org>".
181
182
183	=cut
184