Re: Re: Re: Hex to decimal

[Albannach]

D:\Perl\dl>perl -e "print unpack('s',pack 's', hex('ffaa'))"
-86

This:

• takes the string 'ffaa' and makes a decimal value with hex
• packs that value into a signed short
• unpacks that structure as a signed short
• and prints it

--
I'd like to be able to assign to an luser

[tye]

Note that pack/unpack were not useful in converting from hex to decimal (unlike most people seem to think) but were used here to convert from unsiged to signed-short.

Also, sprintf isn't useful for converting from hex to decimal but is the proper choice for going the other direction.

Update: Ah, thanks merlyn; I didn't think of that way to use pack/unpack to convert hex to decimal. To convert without having to worry about little-/big-endian issues gets rather complicated when using pack/unpack and signed values:

my $hex= "FFAA";
my $signed= unpack "s", pack "S", unpack "v", pack "H*", $hex;

and it gets even more complicated if you want to handle different numbers of hex digits:

my $hex= "ABC";
my $unsigned= unpack "V", pack "h*", "".reverse "00000000".$hex;
my $signed= unpack "l", pack "L", unpack "V", pack "h*",
    "".reverse(  ( $hex=~/^[89a-f]/i ? "F" : "0" ) x 8 . $hex  );

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

[merlyn]

You can skip the hex step with:

perl -e 'print unpack "s", pack "H*", "ffaa"'

If that's wrong on your system, it's an endian problem. {grin} So you can also try:

print unpack "s", pack "h*", scalar reverse "ffaa";

which does print -86 on my machine.

-- Randal L. Schwartz, Perl hacker