perlfaq4 - tweaks for "How do I convert between numeric representations"
[email protected] (Iain Truskett)
| Newsgroups | perl.perlfaq.workers |
|---|---|
| Message-ID | <[email protected]> |
Attached are some diffs that accomplish the following things for the radix conversion. 1. Some common synonyms added to the heading (for keyword searches) 2. Consistent use of ':' on the 'Using...' parts. 3. Useless use of sprintf removed. 4. Mention both %X and %x for dec->hex. 5. Mention ord's ability to convert binary numbers. 6. Mention sprintf's %b on 5.6+. cheers, -- Iain.
radix.patch
(text/plain, 2.8 KB)
--- perlfaq/perlfaq4.pod 2003-08-23 16:08:43.000000000 +1000
+++ pod/perlfaq4.pod 2003-08-23 23:22:24.000000000 +1000
@@ -102,7 +102,7 @@ Perl numbers whose absolute values are i
machines) will work pretty much like mathematical integers. Other numbers
are not guaranteed.
-=head2 How do I convert between numeric representations?
+=head2 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
@@ -121,18 +121,15 @@ programmers the notation might be famili
Using perl's built in conversion of 0x notation:
- $int = 0xDEADBEEF;
- $dec = sprintf("%d", $int);
+ $dec = 0xDEADBEEF;
Using the hex function:
- $int = hex("DEADBEEF");
- $dec = sprintf("%d", $int);
+ $dec = hex("DEADBEEF");
Using pack:
- $int = unpack("N", pack("H8", substr("0" x 8 . "DEADBEEF", -8)));
- $dec = sprintf("%d", $int);
+ $dec = unpack("N", pack("H8", substr("0" x 8 . "DEADBEEF", -8)));
Using the CPAN module Bit::Vector:
@@ -144,13 +141,14 @@ Using the CPAN module Bit::Vector:
Using sprintf:
- $hex = sprintf("%X", 3735928559);
+ $hex = sprintf("%X", 3735928559); # upper case A-F
+ $hex = sprintf("%x", 3735928559); # lower case a-f
-Using unpack
+Using unpack:
$hex = unpack("H*", pack("N", 3735928559));
-Using Bit::Vector
+Using Bit::Vector:
use Bit::Vector;
$vec = Bit::Vector->new_Dec(32, -559038737);
@@ -167,13 +165,11 @@ And Bit::Vector supports odd bit counts:
Using Perl's built in conversion of numbers with leading zeros:
- $int = 033653337357; # note the leading 0!
- $dec = sprintf("%d", $int);
+ $dec = 033653337357; # note the leading 0!
Using the oct function:
- $int = oct("33653337357");
- $dec = sprintf("%d", $int);
+ $dec = oct("33653337357");
Using Bit::Vector:
@@ -188,7 +184,7 @@ Using sprintf:
$oct = sprintf("%o", 3735928559);
-Using Bit::Vector
+Using Bit::Vector:
use Bit::Vector;
$vec = Bit::Vector->new_Dec(32, -559038737);
@@ -199,13 +195,18 @@ Using Bit::Vector
Perl 5.6 lets you write binary numbers directly with
the 0b notation:
- $number = 0b10110110;
+ $number = 0b10110110;
+
+Using ord:
+
+ my $input = "10110110";
+ $decimal = ord( "0b$input" );
-Using pack and ord
+Using pack and ord:
$decimal = ord(pack('B8', '10110110'));
-Using pack and unpack for larger strings
+Using pack and unpack for larger strings:
$int = unpack("N", pack("B32",
substr("0" x 32 . "11110101011011011111011101111", -32)));
@@ -220,6 +221,10 @@ Using Bit::Vector:
=item 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));