… | |
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4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use common::sense; |
7 | use common::sense; |
8 | |
8 | |
9 | # roughly the same as, with much lower memory usage: |
9 | # supposed to be the same, with much lower memory usage, as: |
10 | # |
10 | # |
11 | # use strict qw(vars subs); |
11 | # use strict qw(vars subs); |
12 | # use feature qw(say state switch); |
12 | # use feature qw(say state switch); |
13 | # no warnings; |
13 | # no warnings; |
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14 | # use warnings qw(FATAL closed threads internal debugging pack substr malloc |
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15 | # unopened portable prototype inplace io pipe unpack regexp |
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16 | # deprecated exiting glob digit printf utf8 layer |
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17 | # reserved parenthesis taint closure semicolon); |
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18 | # no warnings qw(exec newline); |
14 | |
19 | |
15 | =head1 DESCRIPTION |
20 | =head1 DESCRIPTION |
16 | |
21 | |
17 | This module implements some sane defaults for Perl programs, as defined by |
22 | 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 |
23 | two typical (or not so typical - use your common sense) specimens of Perl |
19 | Perl coders. |
24 | coders. In fact, after working out details on which warnings and strict |
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25 | modes to enable and make fatal, we found that we (and our code written so |
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26 | far, and others) fully agree on every option, even though we never used |
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27 | warnings before, so it seems this module indeed reflects a "common" sense |
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28 | among some long-time Perl coders. |
20 | |
29 | |
21 | =over 4 |
30 | =over 4 |
22 | |
31 | |
23 | =item no warnings |
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24 | |
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25 | The dreaded warnings. Even worse, the horribly dreaded C<-w> switch. Even |
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26 | though we don't care if other people use warnings (and certainly there are |
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27 | useful ones), a lot of warnings simply go against the spirit of Perl, most |
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28 | prominently, the warnings related to C<undef>. There is nothing wrong with |
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29 | C<undef>: it has well-defined semantics, it is useful, and spitting out |
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30 | warnings you never asked for is just evil. |
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31 | |
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32 | So every module needs C<no warnings> to avoid somebody accidentally using |
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33 | C<-w> and forcing his bad standards on our code. No will do. |
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34 | |
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35 | Funnily enough, L<perllexwarn> explicitly mentions C<-w> (and not in a |
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36 | favourable way), but standard utilities, such as L<prove>, or MakeMaker |
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37 | when running C<make test> enable them blindly. |
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38 | |
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39 | =item use strict qw(subs vars) |
32 | =item use strict qw(subs vars) |
40 | |
33 | |
41 | Using C<use strict> is definitely common sense, but C<use strict |
34 | Using C<use strict> is definitely common sense, but C<use strict |
42 | 'refs'> definitely overshoots it's usefulness. After almost two |
35 | 'refs'> definitely overshoots its usefulness. After almost two |
43 | decades of Perl hacking, we decided that it does more harm than being |
36 | decades of Perl hacking, we decided that it does more harm than being |
44 | useful. Specifically, constructs like these: |
37 | useful. Specifically, constructs like these: |
45 | |
38 | |
46 | @{ $var->[0] } |
39 | @{ $var->[0] } |
47 | |
40 | |
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49 | scope, and C<$var> can legally be C<undef>: |
42 | scope, and C<$var> can legally be C<undef>: |
50 | |
43 | |
51 | @{ $var->[0] || [] } |
44 | @{ $var->[0] || [] } |
52 | |
45 | |
53 | This is annoying, and doesn't shield against obvious mistakes such as |
46 | This is annoying, and doesn't shield against obvious mistakes such as |
54 | using C<"">, so one would even have to write: |
47 | using C<"">, so one would even have to write (at least for the time |
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48 | being): |
55 | |
49 | |
56 | @{ defined $var->[0] ? $var->[0] : [] } |
50 | @{ defined $var->[0] ? $var->[0] : [] } |
57 | |
51 | |
58 | ... which nobody with a bit of common sense would consider |
52 | ... which nobody with a bit of common sense would consider |
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53 | writing: clear code is clearly something else. |
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54 | |
59 | writing. Curiously enough, sometimes, perl is not so strict, as this works |
55 | Curiously enough, sometimes perl is not so strict, as this works even with |
60 | even with C<use strict> in scope: |
56 | C<use strict> in scope: |
61 | |
57 | |
62 | for (@{ $var->[0] }) { ... |
58 | for (@{ $var->[0] }) { ... |
63 | |
59 | |
64 | If that isnt hipocrasy! And all that from a mere program! |
60 | If that isn't hypocrisy! And all that from a mere program! |
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61 | |
65 | |
62 | |
66 | =item use feature qw(say state given) |
63 | =item use feature qw(say state given) |
67 | |
64 | |
68 | We found it annoying that we always have to enable extra features. If |
65 | 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 |
66 | 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 |
67 | it. 5.10 broke almost all our XS modules and nobody cared either (or at |
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68 | least I know of nobody who really complained about gratuitous changes - |
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69 | as opposed to bugs). |
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70 | |
71 | modules that are no longer maintained work with newer versions of Perl, |
71 | Few modules that are not actively maintained work with newer versions of |
72 | regardless of use feature. |
72 | Perl, regardless of use feature or not, so a new major perl release means |
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73 | changes to many modules - new keywords are just the tip of the iceberg. |
73 | |
74 | |
74 | If your code isn't alive, it's dead, jim. |
75 | If your code isn't alive, it's dead, Jim - be an active maintainer. |
75 | |
76 | |
76 | =item much less memory |
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77 | |
77 | |
78 | Just using all those pragmas together wastes <blink>I<< B<776> kilobytes |
78 | =item no warnings, but a lot of new errors |
79 | >></blink> of precious memory in my perl, for I<every single perl process |
79 | |
80 | using our code>, which on our machines, is a lot. In comparison, this |
80 | Ah, the dreaded warnings. Even worse, the horribly dreaded C<-w> |
81 | module only uses I<< B<four> >> kilobytes (I even had to write it out so |
81 | switch: Even though we don't care if other people use warnings (and |
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82 | certainly there are useful ones), a lot of warnings simply go against the |
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83 | spirit of Perl. |
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84 | |
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85 | Most prominently, the warnings related to C<undef>. There is nothing wrong |
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86 | with C<undef>: it has well-defined semantics, it is useful, and spitting |
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87 | out warnings you never asked for is just evil. |
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88 | |
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89 | The result was that every one of our modules did C<no warnings> in the |
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90 | past, to avoid somebody accidentally using and forcing his bad standards |
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91 | on our code. Of course, this switched off all warnings, even the useful |
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92 | ones. Not a good situation. Really, the C<-w> switch should only enable |
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93 | warnings for the main program only. |
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94 | |
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95 | Funnily enough, L<perllexwarn> explicitly mentions C<-w> (and not in a |
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96 | favourable way, calling it outright "wrong"), but standard utilities, such |
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97 | as L<prove>, or MakeMaker when running C<make test>, still enable them |
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98 | blindly. |
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99 | |
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100 | For version 2 of common::sense, we finally sat down a few hours and went |
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101 | through I<every single warning message>, identifiying - according to |
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102 | common sense - all the useful ones. |
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103 | |
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104 | This resulted in the rather impressive list in the SYNOPSIS. When we |
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105 | weren't sure, we didn't include the warning, so the list might grow in |
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106 | the future (we might have made a mistake, too, so the list might shrink |
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107 | as well). |
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108 | |
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109 | Note the presence of C<FATAL> in the list: we do not think that the |
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110 | conditions caught by these warnings are worthy of a warning, we I<insist> |
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111 | that they are worthy of I<stopping> your program, I<instantly>. They are |
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112 | I<bugs>! |
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113 | |
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114 | Therefore we consider C<common::sense> to be much stricter than C<use |
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115 | warnings>, which is good if you are into strict things (we are not, |
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116 | actually, but these things tend to be subjective). |
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117 | |
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118 | After deciding on the list, we ran the module against all of our code that |
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119 | uses C<common::sense> (that is almost all of our code), and found only one |
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120 | occurence where one of them caused a problem: one of elmex's (unreleased) |
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121 | modules contained: |
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122 | |
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123 | $fmt =~ s/([^\s\[]*)\[( [^\]]* )\]/\x0$1\x1$2\x0/xgo; |
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124 | |
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125 | We quickly agreed that indeed the code should be changed, even though it |
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126 | happened to do the right thing when the warning was switched off. |
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127 | |
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128 | |
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129 | =item mucho reduced memory usage |
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130 | |
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131 | Just using all those pragmas mentioned in the SYNOPSIS together wastes |
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132 | <blink>I<< B<776> kilobytes >></blink> of precious memory in my perl, for |
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133 | I<every single perl process using our code>, which on our machines, is a |
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134 | lot. In comparison, this module only uses I<< B<four> >> kilobytes (I even |
82 | it looks like more) of memory on the same platform. |
135 | had to write it out so it looks like more) of memory on the same platform. |
83 | |
136 | |
84 | The money/time/effort/electricity invested in these gigabytes (probably |
137 | The money/time/effort/electricity invested in these gigabytes (probably |
85 | petabytes globally!) of wasted memory could easily save 42 trees, and a |
138 | petabytes globally!) of wasted memory could easily save 42 trees, and a |
86 | kitten! |
139 | kitten! |
87 | |
140 | |
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141 | Unfortunately, until everybods applies more common sense, there will still |
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142 | often be modules that pull in the monster pragmas. But one can hope... |
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143 | |
88 | =cut |
144 | =cut |
89 | |
145 | |
90 | package common::sense; |
146 | package common::sense; |
91 | |
147 | |
92 | our $VERSION = '0.04'; |
148 | our $VERSION = '2.01'; |
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149 | |
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150 | # paste this into perl to find bitmask |
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151 | |
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152 | # no warnings; |
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153 | # use warnings qw(FATAL closed threads internal debugging pack substr malloc unopened portable prototype |
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154 | # inplace io pipe unpack regexp deprecated exiting glob digit printf |
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155 | # utf8 layer reserved parenthesis taint closure semicolon); |
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156 | # no warnings qw(exec newline); |
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157 | # BEGIN { warn join "", map "\\x$_", unpack "(H2)*", ${^WARNING_BITS}; exit 0 }; |
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158 | |
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159 | # overload should be included |
93 | |
160 | |
94 | sub import { |
161 | sub import { |
95 | # no warnings |
162 | # verified with perl 5.8.0, 5.10.0 |
96 | ${^WARNING_BITS} ^= ${^WARNING_BITS}; |
163 | ${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\xfc\x3f\xf3\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x03"; |
97 | |
164 | |
98 | # use strict vars subs |
165 | # use strict vars subs |
99 | $^H |= 0x00000600; |
166 | $^H |= 0x00000600; |
100 | |
167 | |
101 | # use feature |
168 | # use feature |
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117 | =head1 STABILITY AND FUTURE VERSIONS |
184 | =head1 STABILITY AND FUTURE VERSIONS |
118 | |
185 | |
119 | Future versions might change just about everything in this module. We |
186 | 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 |
187 | 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 |
188 | this module, and leave you standing in the rain because we didn't tell |
122 | you. |
189 | you. In fact, we did so when switching from 1.0 to 2.0, which enabled gobs |
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190 | of warnings, and made them FATAL on top. |
123 | |
191 | |
124 | Most likely, we will pick a few useful warnings, instead of just disabling |
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125 | all of them. And maybe we will load some nifty modules that try to emulate |
192 | Maybe we will load some nifty modules that try to emulate C<say> or so |
126 | C<say> or so with perls older than 5.10 (this module, of course, should |
193 | with perls older than 5.10 (this module, of course, should work with older |
127 | work with older perl versions - supporting 5.8 for example is just common |
194 | perl versions - supporting 5.8 for example is just common sense at this |
128 | sense at this time. Maybe not in the future, but of course you can trust |
195 | time. Maybe not in the future, but of course you can trust our common |
129 | our common sense). |
196 | sense to be consistent with, uhm, our opinion). |
130 | |
197 | |
131 | |
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132 | =head1 WHAT OTHER PEOPLE HAVE TO SAY ABOUT THIS MODULE |
198 | =head1 WHAT OTHER PEOPLE HAD TO SAY ABOUT THIS MODULE |
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199 | |
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200 | apeiron |
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201 | |
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202 | "... wow" |
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203 | "I hope common::sense is a joke." |
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204 | |
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205 | crab |
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206 | |
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207 | "i wonder how it would be if joerg schilling wrote perl modules." |
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208 | |
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209 | Adam Kennedy |
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210 | |
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211 | "Very interesting, efficient, and potentially something I'd use all the time." |
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212 | [...] |
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213 | "So no common::sense for me, alas." |
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214 | |
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215 | H.Merijn Brand |
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216 | |
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217 | "Just one more reason to drop JSON::XS from my distribution list" |
133 | |
218 | |
134 | Pista Palo |
219 | Pista Palo |
135 | |
220 | |
136 | "Something in short supply these days..." |
221 | "Something in short supply these days..." |
137 | |
222 | |
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166 | |
251 | |
167 | acme |
252 | acme |
168 | |
253 | |
169 | "THERE IS NO 'no common::sense'!!!! !!!! !!" |
254 | "THERE IS NO 'no common::sense'!!!! !!!! !!" |
170 | |
255 | |
171 | crab |
256 | apeiron (meta-comment about us commenting^Wquoting his comment) |
172 | |
257 | |
173 | "i wonder how it would be if joerg schilling wrote perl modules." |
258 | How about quoting this: get a clue, you fucktarded amoeba. |
174 | |
259 | |
175 | H.Merijn Brand |
260 | quanth |
176 | |
261 | |
177 | "Just one more reason to drop JSON::XS from my distribution list" |
262 | common sense is beautiful, json::xs is fast, Anyevent, EV are fast and |
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263 | furious. I love mlehmannware ;) |
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264 | |
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265 | =head1 FREQUQNTLY ASKED QUESTIONS |
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266 | |
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267 | Or frequently-come-up confusions. |
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268 | |
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269 | =over 4 |
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270 | |
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271 | =item Is this module meant to be serious? |
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272 | |
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273 | Yes, we would have put it under the C<Acme::> namespace otherwise. |
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274 | |
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275 | =item But the manpage is written in a funny/stupid/... way? |
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276 | |
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277 | This was meant to make it clear that our common sense is a subjective |
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278 | thing and other people can use their own notions, taking the steam out |
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279 | of anybody who might be offended (as some people are always offended no |
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280 | matter what you do). |
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281 | |
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282 | This was a failure. |
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283 | |
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284 | But we hope the manpage still is somewhat entertaining even though it |
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285 | explains boring rationale. |
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286 | |
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287 | =item Why do you impose your conventions on my code? |
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288 | |
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289 | For some reason people keep thinking that C<common::sense> imposes |
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290 | process-wide limits, even though the SYNOPSIS makes it clear that it works |
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291 | like other similar modules - only on the scope that uses them. |
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292 | |
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293 | So, no, we don't - nobody is forced to use this module, and using a module |
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294 | that relies on common::sense does not impose anything on you. |
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295 | |
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296 | =item Why do you think only your notion of common::sense is valid? |
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297 | |
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298 | Well, we don't, and have clearly written this in the documentation to |
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299 | every single release. We were just faster than anybody else w.r.t. to |
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300 | grabbing the namespace. |
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301 | |
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302 | =item But everybody knows that you have to use strict and use warnings, |
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303 | why do you disable them? |
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304 | |
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305 | Well, we don't do this either - we selectively disagree with the |
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306 | usefulness of some warnings over others. This module is aimed at |
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307 | experienced Perl programmers, not people migrating from other languages |
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308 | who might be surprised about stuff such as C<undef>. |
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309 | |
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310 | In fact, this module is considerably I<more> strict than the canonical |
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311 | C<use strict; use warnings>, as it makes all warnings fatal in nature, so |
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312 | you can get away with as many things as with the canonical approach. |
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313 | |
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314 | This was not implemented in version 1.0 because of the daunting number |
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315 | of warning categories and the difficulty in getting exactly the set of |
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316 | warnings you wish (i.e. look at the SYNOPSIS in how complicated it is to |
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317 | get a specific set of warnings - it is not reasonable to put this into |
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318 | every module, the maintainance effort would be enourmous). |
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319 | |
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320 | =item But many modules C<use strict> or C<use warnings>, so the memory |
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321 | savings do not apply? |
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322 | |
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323 | I am suddenly so sad. |
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324 | |
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325 | But yes, that's true. Fortunately C<common::sense> still uses only a |
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326 | miniscule amount of RAM. |
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327 | |
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328 | =item But it adds another dependency to your modules! |
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329 | |
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330 | It's a fact, yeah. But it's trivial to install, most popular modules have |
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331 | many more dependencies and we consider dependencies a good thing - it |
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332 | leads to better APIs, more thought about interworking of modules and so |
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333 | on. |
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334 | |
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335 | =item But! But! |
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336 | |
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337 | Yeah, we know. |
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338 | |
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339 | =back |
178 | |
340 | |
179 | =head1 AUTHOR |
341 | =head1 AUTHOR |
180 | |
342 | |
181 | Marc Lehmann <schmorp@schmorp.de> |
343 | Marc Lehmann <schmorp@schmorp.de> |
182 | http://home.schmorp.de/ |
344 | http://home.schmorp.de/ |
183 | |
345 | |
184 | Robin Redeker, "<elmex at ta-sa.org>". |
346 | Robin Redeker, "<elmex at ta-sa.org>". |
185 | |
347 | |
186 | |
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187 | =cut |
348 | =cut |
188 | |
349 | |