Hello Jim,
Tuesday, January 27, 2004, 7:46:33 PM, you wrote:
JH> $Bill Luebkert in <[EMAIL PROTECTED]>:
>> Jim Hill wrote:
>>
>> > Flags=1414
>> >
>> > Is there a module or a perl algorithm for determining which of
>> > the 14 checkboxes are enabled from a "Flags=" value?
>>
>> I would just use a hash and for loop. eg:
JH> I suspected that there might be solution completely outside my
JH> ken. Thanks $Bill, another brilliant response.
>> use strict;
>> my $flags = 2;
>> my %hash = (1 => 'Subscriber is Suspended', 2 => 'Receives List Messages', ...);
>> foreach (sort keys %hash) {
>> print "$hash{$_}\n" if $flags & $_;
>> }
JH> I don't follow that. How are the keys in the hash processed such
JH> that they sum to the $flags value?
Each value is assigned, in turn, to $_. $_ is then "and"ed with the
flags value.
JH> Is it possible to get the matching hash values to print out in
JH> the same order in which the hash was initialised?
A bitwise and (&) will return true if the flag bit is true in a value.
Eg:
1414 & 1024 == true # text/plain digests.
This might make more sense in binary:
10110000110 # 1414
& 10000000000 # 1024
== 10000000000; # true
Bitwise and sets each bit in the return value to 1 if both input bits
at the same position are 1. And remember, any non-zero value is a
"true" boolean (At least in C, I can only assume the same about perl
:P).
I also wanted to point out that the binary value for 1414 posted by
Mark Messenger is a bit wild. I would suggest against using unpack (at
least in that form) to get the binary values of perl integers. Unpack
seems to get some of the underlying data structure or at least the
binary machine representation in the unpacking.
Eg:
print unpack(b16,1);
10001100
print unpack(b16,2);
01001100
print unpack(b16,1414);
1000110000101100
print unpack(b16,14);
1000110000101100
print unpack(b32,1414);
10001100001011001000110000101100
It looks like perl's integer data-type is 1 byte per decimal place
with the left four bits representing decimal values 0-9 (little
endian). The right four bits seem to always be "1100".
Heck, those look like the (reversed) ascii values of the characters to
me.
00110000 0
00110001 1
00110010 2
00110011 3
00110100 4
00110101 5
00110110 6
00110111 7
00111000 8
00111001 9
Woops, I guess so (just looked it up). Is there some way to force
unpack to do this using the integer value? & seems immune,
fortunately.
--
Best regards,
Sam mailto:[EMAIL PROTECTED]
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