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RE: RE: Randomizing Unique ID?

by tye (Sage)
on Aug 09, 2000 at 21:54 UTC ( #27123=note: print w/replies, xml ) Need Help??

in reply to RE: Randomizing Unique ID?
in thread Randomizing Unique ID?

Note that this is barely adequate since a "typical" double has 53 bits of mantissa (not counting the sign bit) which can handle just under 16 decimal digits while time() currently returns 9 digits but will soon return 10, while $$ is typically no more than 5 digits (total will soon be 15 digits).

Doing the conversion to base-62 in two steps would give you lots of room (and different results).

        - tye (but my friends call me "Tye")

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RE: RE: RE: Randomizing Unique ID?
by Adam (Vicar) on Aug 09, 2000 at 22:03 UTC
    Well, If you want more room in the double, then do the base conversion before doing the concatenation, thusly:
    # Generate a truly unique ID sub GenerateBase { my $base = shift; $base = 62 if $base > 62; my @nums = (0..9,'a'..'z','A'..'Z')[0..$base-1]; return sub { my $number = shift; my $rep = ""; # this will be the end value. while( $number > 0 ) { $rep = $nums[$number % $base] . $rep; $number = int( $number / $base ); } return $rep; } } my $ToBase62 = GenerateBase( 62 ); my $ID = $ToBase62->( $$ ) . $ToBase62->( time );

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[LanX]: Choroba: do you miss chaos with ties? apply at the US government.. ;)
[ambrus]: Corion: those are good rules.
[ambrus]: Discipulus: oh sure. the input data has different filenames every time I get them.
[ambrus]: the directory structure may be 1, 2, or 3 deep, it may have spaces in the filename or not, it has dates in various format, different keywords for the same meanings, and the dates and other keywords are assembled in various ways.
[Discipulus]: no ambrus by specification i mean for example license per core instead of per socket, so fields are different

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