Re^4: Portability of floor(log(N))

And, IIUC, the test script should accept '1000e-36' as correct when NV precision is 64 bits

Alternatively (and since you're already using POSIX) you should get the result you expected, if you replace the log() calls with POSIX::log10(). That way both numerator and divisor should be exact (for these particular inputs), as should also be the result of the division ... irrespective of the precision of the NV:

$ perl -MPOSIX -le 'print POSIX::floor(POSIX::log10(1e-33) / POSIX::lo
+g10(1000));'
-11
[download]

Cheers,
Rob

Comment on Re^4: Portability of floor(log(N)) Download Code

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Re^5: Portability of floor(log(N)) by toolic (Bishop) on Mar 14, 2018 at 17:31 UTC
Using POSIX::log10() looks like the simplest solution. I will attempt to pester the tester with a modified version of FormatEng.pm. Do you think I can simplify it by replacing POSIX::log10(1000) with 3, or will it be better to keep your code as-is? `my $e = floor( POSIX::log10($num) / 3 );` [download]	[reply] [d/l]
Re^6: Portability of floor(log(N)) by pryrt (Abbot) on Mar 14, 2018 at 18:22 UTC
log10(1000) will never change, and is exactly 3, so there's no reason not to use it	[reply]