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| Code Block | ||||
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our $BufferSize = 512;
# ...
my $nblocks = 1 + (($nbytes - 1) >> 9); # because $BufferSize = 512 = 2^9
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The programmer might assume that " everyone knows $BufferSize equals 512 " and that right-shifting 9 bits is the same (for positive numbers) as dividing by 512. But if $BufferSize changes to 1024 on some systems, the subsequent expression must also be updated and can be overlooked easily. This makes modifications of constants difficult and error prone.
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| Code Block | ||||
|---|---|---|---|---|
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my $nblocks = 1 + (($nbytes - 1) / $BufferSize;
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Tool | Diagnostic |
|---|---|
Perl::Critic | ValuesAndExpressions::ProhibitMagicNumbers |
Related Guidelines
Bibliography
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|http://search.cpan.org/~elliotjs/Perl-Critic-1.116/] [ProhibitMagicNumbers|http://search.cpan.org/dist/Perl-Critic/lib/Perl/Critic/Policy/ValuesAndExpressions/ProhibitMagicNumbers.pm]
\[[Wall 2011|AA. Bibliography#Manpages]\] [perlfunc|http://perldoc.perl.org/perlfunc.html]
02. Expressions