Color me crazy, but why do you want to spend the time calculating 2**30 when you may not even use it?!? 

% perl -MO=Deparse -e 'print 2**30'
print 1073741824;
-e syntax OK

[download]

(1) Calculating 2 ** $n, where n is a human-scale integer, is ridiculously easy and cheap for computers to do. It's just a bit shifting operation.

(2) Sub-expressions consisting of constants, such as (2**30) are computed during the compilation stage, not the runtime stage, as demonstrated above. In Perl this doesn't matter that much for runtime savings, since you must compile on every run, but why not use Perl's compiler to do the work instead of expressing yet more (possibly buggy) Perl code to be interpreted to accomplish the same calculation?

(3) Yes, I said possibly buggy. In your first map definition, you define KB, MB and GB as consecutive multiples of ten, not consecutive powers of 1000. If a maintenance programmer would find the numeric literal or simple expression more readable than the code that derives those values, please, use the numbers!

Update: Okay, you wanted 10, 20, 30 for KB, MB, GB, just to do a runtime 2**$e later. I still say this doesn't save resources and it doesn't make it more readable. But I'll grant it's what you intended, and not a bug. :)

--
[ e d @ h a l l e y . c c ]

In reply to Re: Re: Re: why is this code bad under -w option? by halley
in thread why is this code bad under -w option? by Grygonos

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