/ 
common-sense-2.0
River stage four • 163 direct dependents • 2380 total dependents
/ common::sense

NAME

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

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;
# use warnings qw(FATAL closed threads internal debugging pack substr malloc
#                 unopened portable prototype inplace io pipe unpack regexp
#                 deprecated exiting glob digit printf utf8 layer
#                 reserved parenthesis taint closure semicolon);
# no warnings qw(exec newline);

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.

use strict qw(subs vars)

Using use strict is definitely common sense, but 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 use strict 'refs' is in scope, and $var can legally be undef:

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

This is annoying, and doesn't shield against obvious mistakes such as using "", 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 use strict in scope:

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

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

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 least I know of nobody who really complained about gratuitous 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.

no warnings, but a lot of new errors

Ah, the dreaded warnings. Even worse, the horribly dreaded -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 undef. There is nothing wrong with undef: it has well-defined semantics, it is useful, and spitting out warnings you never asked for is just evil.

The result was that every one of our modules did no warnings in the past, to avoid somebody accidentally using and forcing his bad standards on our code. Of course, this switched off all warnings, even the useful ones. Not a good situation. Really, the -w switch should only enable warnings for the main program only.

Funnily enough, perllexwarn explicitly mentions -w (and not in a favourable way, calling it outright "wrong"), but standard utilities, such as prove, or MakeMaker when running make test, still enable them blindly.

For version 2 of common::sense, we finally sat down a few hours and went through every single warning message, identifiying - according to common sense - all the useful ones.

This resulted in the rather impressive list in the SYNOPSIS. When we weren't sure, we didn't include the warning, so the list might grow in the future (we might have made a mistake, too, so the list might shrink as well).

Note the presence of FATAL in the list: we do not think that the conditions caught by these warnings are worthy of a warning, we insist that they are worthy of stopping your program, instantly. They are bugs!

Therefore we consider common::sense to be much stricter than use warnings, which is good if you are into strict things (we are not, actually, but these things tend to be subjective).

After deciding on the list, we ran the module against all of our code that uses common::sense (that is almost all of our code), and found only one occurence where one of them caused a problem: one of elmex's (unreleased) modules contained:

$fmt =~ s/([^\s\[]*)\[( [^\]]* )\]/\x0$1\x1$2\x0/xgo;

We quickly agreed that indeed the code should be changed, even though it happened to do the right thing when the warning was switched off.

mucho reduced memory usage

Just using all those pragmas mentioned in the SYNOPSIS together wastes <blink>776 kilobytes</blink> of precious memory in my perl, for every single perl process using our code, which on our machines, is a lot. In comparison, this module only uses 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...

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?

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. In fact, we did so when switching from 1.0 to 2.0, which enabled gobs of warnings, and made them FATAL on top.

Maybe we will load some nifty modules that try to emulate 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).

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

apeiron (meta-comment about us commenting^Wquoting his comment)

How about quoting this: get a clue, you fucktarded amoeba.

AUTHOR

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

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