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Perl Documentation

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
print hex("0x1234567890123490"),"\n"; # Perl v5.10.0 or later
{
  no bigint;
  print 2 ** 256,"\n";                # a normal Perl scalar now
}
# Import into current package:
use bigint qw/hex oct/;
print hex("0x1234567890123490"),"\n";
print oct("01234567890123490"),"\n";

DESCRIPTION

All operators (including basic math operations) except the range operator .. are overloaded. Integer constants are created as proper BigInts.

Floating point constants are truncated to integer. All parts and results of expressions are also truncated.

Unlike integer, this pragma creates integer constants that are only limited in their size by the available memory and CPU time.

use integer vs. use bigint

There is one small difference between use integer and use bigint: the former will not affect assignments to variables and the return value of some functions. bigint truncates these results to integer too:

# perl -Minteger -wle 'print 3.2'
3.2
# perl -Minteger -wle 'print 3.2 + 0'
3
# perl -Mbigint -wle 'print 3.2'
3
# perl -Mbigint -wle 'print 3.2 + 0'
3
# perl -Mbigint -wle 'print exp(1) + 0'
2
# perl -Mbigint -wle 'print exp(1)'
2
# perl -Minteger -wle 'print exp(1)'
2.71828182845905
# perl -Minteger -wle 'print exp(1) + 0'
2

In practice this makes seldom a difference as parts and results of expressions will be truncated anyway, but this can, for instance, affect the return value of subroutines:

sub three_integer { use integer; return 3.2; }
sub three_bigint { use bigint; return 3.2; }
print three_integer(), " ", three_bigint(),"\n";    # prints "3.2 3"

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:

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 bignum lib => 'GMP';

The following would first try to find Math::BigInt::Foo, then Math::BigInt::Bar, and when this also fails, revert to Math::BigInt::Calc:

use bigint lib => 'Foo,Math::BigInt::Bar';

Using lib warns if none of the specified libraries can be found and Math::BigInt did fall back to one of the default libraries. To suppress this warning, use try instead:

use bignum try => 'GMP';

If you want the code to die instead of falling back, use only instead:

use bignum only => 'GMP';

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'. 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 positive number by 0, and '-inf' when dividing any negative number by 0.

Method calls

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.

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 being 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 test that the 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.

Methods

CAVEATS

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'
perl -Mbignum=a,65,l,GMP -le 'print 7 ** 7777'

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::BigInt::Pari and Math::BigInt::GMP.

AUTHORS

(C) by Tels http://bloodgate.com/ in early 2002 - 2007.