bigint
bigint(3) Perl Programmers Reference Guide bigint(3)
NAME
bigint - Transparent BigInteger support for Perl
SYNOPSIS
use bigint;
$x = 2 + 4.5,"\n"; # BigInt 6
print 2 ** 512,"\n"; # really is what you think it is
print inf + 42,"\n"; # inf
print NaN * 7,"\n"; # NaN
DESCRIPTION
All operators (including basic math operations) are overloaded. Integer
constants are created as proper BigInts.
Floating point constants are truncated to integer. All results are also
truncated.
OPTIONS
bigint recognizes some options that can be passed while loading it via
use. The options can (currently) be either a single letter form, or
the long form. The following options exist:
a or accuracy
This sets the accuracy for all math operations. The argument must be
greater than or equal to zero. See Math::BigInt's bround() function
for details.
perl -Mbigint=a,2 -le 'print 12345+1'
p or precision
This sets the precision for all math operations. The argument can be
any integer. Negative values mean a fixed number of digits after the
dot, and are <B>ignored</B> since all operations happen in integer
space. A positive value rounds to this digit left from the dot. 0 or
1 mean round to integer and are ignore like negative values.
See Math::BigInt's bfround() function for details.
perl -Mbignum=p,5 -le 'print 123456789+123'
t or trace
This enables a trace mode and is primarily for debugging bigint or
Math::BigInt.
l or lib
Load a different math lib, see "MATH LIBRARY".
perl -Mbigint=l,GMP -e 'print 2 ** 512'
Currently there is no way to specify more than one library on the
command line. This will be hopefully fixed soon ;)
v or version
This prints out the name and version of all modules used and then
exits.
perl -Mbigint=v -e ''
MATH LIBRARY
Math with the numbers is done (by default) by a module called
Math::BigInt::Calc. This is equivalent to saying:
use bigint lib => 'Calc';
You can change this by using:
use bigint lib => 'BitVect';
The following would first try to find Math::BigInt::Foo, then
Math::BigInt::Bar, and when this also fails, revert to Math::Big-
Int::Calc:
use bigint lib => 'Foo,Math::BigInt::Bar';
Please see respective module documentation for further details.
INTERNAL FORMAT
The numbers are stored as objects, and their internals might change at
anytime, especially between math operations. The objects also might
belong to different classes, like Math::BigInt, or Math::BigInt::Lite.
Mixing them together, even with normal scalars is not extraordinary,
but normal and expected.
You should not depend on the internal format, all accesses must go
through accessor methods. E.g. looking at $x->{sign} is not a good idea
since there is no guaranty that the object in question has such a hash
key, nor is a hash underneath at all.
SIGN
The sign is either '+', '-', 'NaN', '+inf' or '-inf' and stored seper-
ately. You can access it with the sign() method.
A sign of 'NaN' is used to represent the result when input arguments
are not numbers or as a result of 0/0. '+inf' and '-inf' represent plus
respectively minus infinity. You will get '+inf' when dividing a posi-
tive number by 0, and '-inf' when dividing any negative number by 0.
METHODS
Since all numbers are now objects, you can use all functions that are
part of the BigInt API. You can only use the bxxx() notation, and not
the fxxx() notation, though.
CAVEAT
But a warning is in order. When using the following to make a copy of a
number, only a shallow copy will be made.
$x = 9; $y = $x;
$x = $y = 7;
Using the copy or the original with overloaded math is okay, e.g. the
following work:
$x = 9; $y = $x;
print $x + 1, " ", $y,"\n"; # prints 10 9
but calling any method that modifies the number directly will result in
both the original and the copy beeing destroyed:
$x = 9; $y = $x;
print $x->badd(1), " ", $y,"\n"; # prints 10 10
$x = 9; $y = $x;
print $x->binc(1), " ", $y,"\n"; # prints 10 10
$x = 9; $y = $x;
print $x->bmul(2), " ", $y,"\n"; # prints 18 18
Using methods that do not modify, but testthe contents works:
$x = 9; $y = $x;
$z = 9 if $x->is_zero(); # works fine
See the documentation about the copy constructor and "=" in overload,
as well as the documentation in BigInt for further details.
MODULES USED
"bigint" is just a thin wrapper around various modules of the
Math::BigInt family. Think of it as the head of the family, who runs
the shop, and orders the others to do the work.
The following modules are currently used by bigint:
Math::BigInt::Lite (for speed, and only if it is loadable)
Math::BigInt
EXAMPLES
Some cool command line examples to impress the Python crowd ;) You
might want to compare them to the results under -Mbignum or -Mbigrat:
perl -Mbigint -le 'print sqrt(33)'
perl -Mbigint -le 'print 2*255'
perl -Mbigint -le 'print 4.5+2*255'
perl -Mbigint -le 'print 3/7 + 5/7 + 8/3'
perl -Mbigint -le 'print 123->is_odd()'
perl -Mbigint -le 'print log(2)'
perl -Mbigint -le 'print 2 ** 0.5'
perl -Mbigint=a,65 -le 'print 2 ** 0.2'
LICENSE
This program is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.
SEE ALSO
Especially bigrat as in "perl -Mbigrat -le 'print 1/3+1/4'" and bignum
as in "perl -Mbignum -le 'print sqrt(2)'".
Math::BigInt, Math::BigRat and Math::Big as well as Math::Big-
Int::BitVect, Math::BigInt::Pari and Math::BigInt::GMP.
AUTHORS
(C) by Tels <http://bloodgate.com/> in early 2002, 2003.
perl v5.8.6 2001-09-21 bigint(3)
