Re: Run length encode a bit vector

Not sure if this helps or not:

use strict;
use warnings;

my $bytes = pack 'N', 0x01020304;
my $bits = unpack('B32', $bytes);
my @counts;

while ($bits =~ /(0+|1+)/g) {
    push @counts, length($1) * (substr($1, 0, 1) == 1 ? 1 : -1);
}

print "$bits\n@counts";
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Output:

00000001000000100000001100000100
-7 1 -6 1 -7 2 -5 1 -2
[download]

Comment on Re: Run length encode a bit vector Select or Download Code

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Re^2: Run length encode a bit vector by ikegami (Patriarch) on Jan 05, 2012 at 19:28 UTC
The parent could use `B` instead of `B32`. Methods that rely on `unpack('B', $bytes)` can even handle arbitrary long packed string if they are packed in "network" (big endian) order. `my $bytes = pack 'N', 0x01020304, 0x05060708; my $bits = unpack 'B', $bytes; ...` [download] (By the way, the `== 1` is superfluous in the parent's code.)	[reply] [d/l] [select]
Re^3: Run length encode a bit vector by TJPride (Pilgrim) on Jan 05, 2012 at 20:42 UTC
Odd, I would have thought that 0 as a string would still trigger true, and that in this context the pattern match would return 0 as a string. But I tested just now and you're correct, it works the same way without the ==.	[reply]
Re^4: Run length encode a bit vector by ikegami (Patriarch) on Jan 05, 2012 at 20:59 UTC
Zero is false, no matter if it's stored in an IV, UV, NV or PV.	[reply]