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 v5.9.4 or later
{
no bigint;
print 2 ** 256,"\n"; # a normal Perl scalar now
}
# Note that this will be global:
use bigint qw/hex oct/;
print hex("0x1234567890123490"),"\n";
print oct("01234567890123490"),"\n";
DESCRIPTION
All operators (including basic math operations) 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 integerand
use bigint: the former will not affect assignments to variables and the return value of some functions.
biginttruncates 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:
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
Note that setting precision and accurary at the same time is not possible. 
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
Note that setting precision and accurary at the same time is not possible. 
t or trace  This enables a trace mode and is primarily for debugging bigint or Math::BigInt. 
hex  Override the builtin hex() method with a version that can handle big integers. Note that under Perl v5.9.4 or ealier, this will be global and cannot be disabled with no bigint;. 
oct  Override the builtin oct() method with a version that can handle big integers. Note that under Perl v5.9.4 or ealier, this will be global and cannot be disabled with no bigint;. 
l, lib, try or only 
Load a different math lib, see Math Library.
perl Mbigint=lib,GMP e print 2 ** 512
perl Mbigint=try,GMP e print 2 ** 512
perl Mbigint=only,GMP e print 2 ** 512
Currently there is no way to specify more than one library on the command line. This means the following does not work:
perl Mbignum=l,GMP,Pari e print 2 ** 512
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

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
libwarns if none of the specified libraries can be found and Math::BigInt did fall back to one of the default libraries. To supress this warning, use
tryinstead:
use bignum try => GMP;
If you want the code to die instead of falling back, use
onlyinstead:
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
$x>{sign} is not a good idea since there is no guaranty that the object in question has such a hash key, nor is a hash underneath at all.
Sign
The sign is either ’+’, ’’, ’NaN’, ’+inf’ or ’inf’. You can access it with the sign() method.
A sign of ’NaN’ is used to represent the result when input arguments are not numbers or as a result of 0/0. ’+inf’ and ’inf’ represent plus respectively minus infinity. You will get ’+inf’ when dividing a positive number by 0, and ’inf’ when dividing any negative number by 0.
Methods
Since all numbers are now objects, you can use all functions that are part of the BigInt API. You can only use the bxxx() notation, and not the fxxx() notation, though.
inf() 
A shortcut to return Math::BigInt>binf(). Useful because Perl does not always
handle bareword infproperly. 
NaN() 
A shortcut to return Math::BigInt>bnan(). Useful because Perl does not always
handle bareword NaNproperly. 
e 
# perl Mbigint=e wle print e
Returns Euler’s number e, aka exp(1). Note that under bigint, this is truncated to an integer, and hence simple ’2’. 
PI 
# perl Mbigint=PI wle print PI
Returns PI. Note that under bigint, this is truncated to an integer, and hence simple ’3’. 
bexp() 
bexp($power,$accuracy);
Returns Euler’s number eraised to the appropriate power, to the wanted accuracy. Note that under bigint, the result is truncated to an integer. Example:
# perl Mbigint=bexp wle print bexp(1,80)

bpi() 
bpi($accuracy);
Returns PI to the wanted accuracy. Note that under bigint, this is truncated to an integer, and hence simple ’3’. Example:
# perl Mbigint=bpi wle print bpi(80)

upgrade() 
Return the class that numbers are upgraded to, is in fact returning
$Math::BigInt::upgrade. 
in_effect() 
use bigint;
print "in effect\n" if bigint::in_effect; # true
{
no bigint;
print "in effect\n" if bigint::in_effect; # false
}
Returns true or false if bigintis in effect in the current scope. This method only works on Perl v5.9.4 or later. 
\s1MATH\s0 \s1LIBRARY\s0
Math with the numbers is done (by default) by a module called
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 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 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.
CAVAETS
in_effect()  This method only works on Perl v5.9.4 or later. 
hex()/oct() 
bigintoverrides these routines with versions that can also handle big integer values. Under Perl prior to version v5.9.4, however, this will not happen unless you specifically ask for it with the two import tags hex and oct  and then it will be global and cannot be disabled inside a scope with no bigint:
use bigint qw/hex oct/;
print hex("0x1234567890123456");
{
no bigint;
print hex("0x1234567890123456");
}
The second call to hex() will warn about a nonportable constant. Compare this to:
use bigint;
# will warn only under Perl older than v5.9.4
print hex("0x1234567890123456");

MODULES USED
bigintis 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+1/4and bignum as in
perl Mbignum le print sqrt(2).
Math::BigInt, Math::BigRat and Math::Big as well as Math::BigInt::BitVect, Math::BigInt::Pari and Math::BigInt::GMP.
AUTHORS
(C) by Tels <http://bloodgate.com/> in early 2002  2007.