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#### PerlFAQ Server

comes with the standard Perl distribution. These postings aim to

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to review and update the answers. The latest version of the complete

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4.5: How do I convert between numeric representations/bases/radixes?

As always with Perl there is more than one way to do it. Below are a few

examples of approaches to making common conversions between number

representations. This is intended to be representational rather than

exhaustive.

Some of the examples later in perlfaq4 use the "Bit::Vector" module from

CPAN. The reason you might choose "Bit::Vector" over the perl built in

functions is that it works with numbers of ANY size, that it is

optimized for speed on some operations, and for at least some

programmers the notation might be familiar.

How do I convert hexadecimal into decimal

Using perl's built in conversion of "0x" notation:

$dec = 0xDEADBEEF;

Using the "hex" function:

$dec = hex("DEADBEEF");

Using "pack":

$dec = unpack("N", pack("H8", substr("0" x 8 . "DEADBEEF", -8)));

Using the CPAN module "Bit::Vector":

use Bit::Vector;

$vec = Bit::Vector->new_Hex(32, "DEADBEEF");

$dec = $vec->to_Dec();

How do I convert from decimal to hexadecimal

Using "sprintf":

$hex = sprintf("%X", 3735928559); # upper case A-F

$hex = sprintf("%x", 3735928559); # lower case a-f

Using "unpack":

$hex = unpack("H*", pack("N", 3735928559));

Using "Bit::Vector":

use Bit::Vector;

$vec = Bit::Vector->new_Dec(32, -559038737);

$hex = $vec->to_Hex();

And "Bit::Vector" supports odd bit counts:

use Bit::Vector;

$vec = Bit::Vector->new_Dec(33, 3735928559);

$vec->Resize(32); # suppress leading 0 if unwanted

$hex = $vec->to_Hex();

How do I convert from octal to decimal

Using Perl's built in conversion of numbers with leading zeros:

$dec = 033653337357; # note the leading 0!

Using the "oct" function:

$dec = oct("33653337357");

Using "Bit::Vector":

use Bit::Vector;

$vec = Bit::Vector->new(32);

$vec->Chunk_List_Store(3, split(//, reverse "33653337357"));

$dec = $vec->to_Dec();

How do I convert from decimal to octal

Using "sprintf":

$oct = sprintf("%o", 3735928559);

Using "Bit::Vector":

use Bit::Vector;

$vec = Bit::Vector->new_Dec(32, -559038737);

$oct = reverse join('', $vec->Chunk_List_Read(3));

How do I convert from binary to decimal

Perl 5.6 lets you write binary numbers directly with the "0b"

notation:

$number = 0b10110110;

Using "oct":

my $input = "10110110";

$decimal = oct( "0b$input" );

Using "pack" and "ord":

$decimal = ord(pack('B8', '10110110'));

Using "pack" and "unpack" for larger strings:

$int = unpack("N", pack("B32",

substr("0" x 32 . "11110101011011011111011101111", -32)));

$dec = sprintf("%d", $int);

# substr() is used to left pad a 32 character string with zeros.

Using "Bit::Vector":

$vec = Bit::Vector->new_Bin(32, "11011110101011011011111011101111");

$dec = $vec->to_Dec();

How do I convert from decimal to binary

Using "sprintf" (perl 5.6+):

$bin = sprintf("%b", 3735928559);

Using "unpack":

$bin = unpack("B*", pack("N", 3735928559));

Using "Bit::Vector":

use Bit::Vector;

$vec = Bit::Vector->new_Dec(32, -559038737);

$bin = $vec->to_Bin();

The remaining transformations (e.g. hex -> oct, bin -> hex, etc.)

are left as an exercise to the inclined reader.

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The perlfaq-workers, a group of volunteers, maintain the perlfaq. They

are not necessarily experts in every domain where Perl might show up,

so please include as much information as possible and relevant in any

corrections. The perlfaq-workers also don't have access to every

operating system or platform, so please include relevant details for

corrections to examples that do not work on particular platforms.

Working code is greatly appreciated.

If you'd like to help maintain the perlfaq, see the details in

perlfaq.pod.