bignum(3perl) Perl Programmers Reference Guide bignum(3perl)
NAME
bignum - transparent big number support for Perl
SYNOPSIS
use bignum;
$x = 2 + 4.5; # Math::BigFloat 6.5
print 2 ** 512 * 0.1; # Math::BigFloat 134...09.6
print 2 ** 512; # Math::BigInt 134...096
print inf + 42; # Math::BigInt inf
print NaN * 7; # Math::BigInt NaN
print hex("0x1234567890123490"); # Perl v5.10.0 or later
{
no bignum;
print 2 ** 256; # a normal Perl scalar now
}
# for older Perls, import into current package:
use bignum qw/hex oct/;
print hex("0x1234567890123490");
print oct("01234567890123490");
DESCRIPTION
Literal numeric constants
By default, every literal integer becomes a Math::BigInt object, and
literal non-integer becomes a Math::BigFloat object. Whether a numeric
literal is considered an integer or non-integers depends only on the
value of the constant, not on how it is represented. For instance, the
constants 3.14e2 and 0x1.3ap8 become Math::BigInt objects, because they
both represent the integer value decimal 314.
The default "use bignum;" is equivalent to
use bignum downgrade => "Math::BigInt", upgrade => "Math::BigFloat";
The classes used for integers and non-integers can be set at compile
time with the "downgrade" and "upgrade" options, for example
# use Math::BigInt for integers and Math::BigRat for non-integers
use bignum upgrade => "Math::BigRat";
Note that disabling downgrading and upgrading does not affect how
numeric literals are converted to objects
# disable both downgrading and upgrading
use bignum downgrade => undef, upgrade => undef;
$x = 2.4; # becomes 2.4 as a Math::BigFloat
$y = 2; # becomes 2 as a Math::BigInt
Upgrading and downgrading
By default, when the result of a computation is an integer, an Inf, or a
NaN, the result is downgraded even when all the operands are instances
of the upgrade class.
use bignum;
$x = 2.4; # becomes 2.4 as a Math::BigFloat
$y = 1.2; # becomes 1.2 as a Math::BigFloat
$z = $x / $y; # becomes 2 as a Math::BigInt due to downgrading
Equivalently, by default, when the result of a computation is a finite
non-integer, the result is upgraded even when all the operands are
instances of the downgrade class.
use bignum;
$x = 7; # becomes 7 as a Math::BigInt
$y = 2; # becomes 2 as a Math::BigInt
$z = $x / $y; # becomes 3.5 as a Math::BigFloat due to upgrading
The classes used for downgrading and upgrading can be set at runtime
with the "downgrade()" and "upgrade()" methods, but see "CAVEATS" below.
The upgrade and downgrade classes don't have to be Math::BigInt and
Math::BigFloat. For example, to use Math::BigRat as the upgrade class,
use
use bignum upgrade => "Math::BigRat";
$x = 2; # becomes 2 as a Math::BigInt
$y = 3.6; # becomes 18/5 as a Math::BigRat
The upgrade and downgrade classes can be modified at runtime
use bignum;
$x = 3; # becomes 3 as a Math::BigInt
$y = 2; # becomes 2 as a Math::BigInt
$z = $x / $y; # becomes 1.5 as a Math::BigFlaot
bignum -> upgrade("Math::BigRat");
$w = $x / $y; # becomes 3/2 as a Math::BigRat
Disabling downgrading doesn't change the fact that literal constant
integers are converted to the downgrade class, it only prevents
downgrading as a result of a computation. E.g.,
use bignum downgrade => undef;
$x = 2; # becomes 2 as a Math::BigInt
$y = 2.4; # becomes 2.4 as a Math::BigFloat
$z = 1.2; # becomes 1.2 as a Math::BigFloat
$w = $x / $y; # becomes 2 as a Math::BigFloat due to no downgrading
If you want all numeric literals, both integers and non-integers, to
become Math::BigFloat objects, use the bigfloat pragma.
Equivalently, disabling upgrading doesn't change the fact that literal
constant non-integers are converted to the upgrade class, it only
prevents upgrading as a result of a computation. E.g.,
use bignum upgrade => undef;
$x = 2.5; # becomes 2.5 as a Math::BigFloat
$y = 7; # becomes 7 as a Math::BigInt
$z = 2; # becomes 2 as a Math::BigInt
$w = $x / $y; # becomes 3 as a Math::BigInt due to no upgrading
If you want all numeric literals, both integers and non-integers, to
become Math::BigInt objects, use the bigint pragma.
You can even do
use bignum upgrade => "Math::BigRat", upgrade => undef;
which converts all integer literals to Math::BigInt objects and all non-
integer literals to Math::BigRat objects. However, when the result of a
computation involving two Math::BigInt objects results in a non-integer
(e.g., 7/2), the result will be truncted to a Math::BigInt rather than
being upgraded to a Math::BigRat, since upgrading is disabled.
Overloading
Since all numeric literals become objects, you can call all the usual
methods from Math::BigInt and Math::BigFloat on them. This even works to
some extent on expressions:
perl -Mbignum -le '$x = 1234; print $x->bdec()'
perl -Mbignum -le 'print 1234->copy()->binc();'
perl -Mbignum -le 'print 1234->copy()->binc()->badd(6);'
Options
"bignum" recognizes some options that can be passed while loading it via
via "use". 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() method
for details.
perl -Mbignum=a,50 -le 'print sqrt(20)'
Note that setting precision and accuracy 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, while a positive value rounds to this digit left from the dot.
0 means round to integer. See Math::BigInt's bfround() method for
details.
perl -Mbignum=p,-50 -le 'print sqrt(20)'
Note that setting precision and accuracy at the same time is not
possible.
l, lib, try, or only
Load a different math lib, see "Math Library".
perl -Mbignum=l,GMP -e 'print 2 ** 512'
perl -Mbignum=lib,GMP -e 'print 2 ** 512'
perl -Mbignum=try,GMP -e 'print 2 ** 512'
perl -Mbignum=only,GMP -e 'print 2 ** 512'
hex Override the built-in hex() method with a version that can handle
big numbers. This overrides it by exporting it to the current
package. Under Perl v5.10.0 and higher, this is not so necessary, as
hex() is lexically overridden in the current scope whenever the
"bignum" pragma is active.
oct Override the built-in oct() method with a version that can handle
big numbers. This overrides it by exporting it to the current
package. Under Perl v5.10.0 and higher, this is not so necessary, as
oct() is lexically overridden in the current scope whenever the
"bignum" pragma is active.
v or version
this prints out the name and version of the modules and then exits.
perl -Mbignum=v
Math Library
Math with the numbers is done (by default) by a backend library module
called Math::BigInt::Calc. The default is equivalent to saying:
use bignum 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 if this also fails, revert to Math::BigInt::Calc:
use bignum lib => 'Foo,Math::BigInt::Bar';
Using c<lib> warns if none of the specified libraries can be found and
Math::BigInt and Math::BigFloat fell 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.
Method calls
Since all numbers are now objects, you can use the methods that are part
of the Math::BigInt and Math::BigFloat API.
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 $x->is_zero(); # works fine
See the documentation about the copy constructor and "=" in overload, as
well as the documentation in Math::BigFloat for further details.
Methods
inf()
A shortcut to return "inf" as an object. Useful because Perl does
not always handle bareword "inf" properly.
NaN()
A shortcut to return "NaN" as an object. Useful because Perl does
not always handle bareword "NaN" properly.
e
# perl -Mbignum=e -wle 'print e'
Returns Euler's number "e", aka exp(1) (= 2.7182818284...).
PI
# perl -Mbignum=PI -wle 'print PI'
Returns PI (= 3.1415926532..).
bexp()
bexp($power, $accuracy);
Returns Euler's number "e" raised to the appropriate power, to the
wanted accuracy.
Example:
# perl -Mbignum=bexp -wle 'print bexp(1,80)'
bpi()
bpi($accuracy);
Returns PI to the wanted accuracy.
Example:
# perl -Mbignum=bpi -wle 'print bpi(80)'
accuracy()
Set or get the accuracy.
precision()
Set or get the precision.
round_mode()
Set or get the rounding mode.
div_scale()
Set or get the division scale.
upgrade()
Set or get the class that the downgrade class upgrades to, if any.
Set the upgrade class to "undef" to disable upgrading. See
"/CAVEATS" below.
downgrade()
Set or get the class that the upgrade class downgrades to, if any.
Set the downgrade class to "undef" to disable upgrading. See
"CAVEATS" below.
in_effect()
use bignum;
print "in effect\n" if bignum::in_effect; # true
{
no bignum;
print "in effect\n" if bignum::in_effect; # false
}
Returns true or false if "bignum" is in effect in the current scope.
This method only works on Perl v5.9.4 or later.
CAVEATS
The upgrade() and downgrade() methods
Note that setting both the upgrade and downgrade classes at runtime
with the "upgrade()" and "downgrade()" methods, might not do what
you expect:
# Assuming that downgrading and upgrading hasn't been modified so far, so
# the downgrade and upgrade classes are Math::BigInt and Math::BigFloat,
# respectively, the following sets the upgrade class to Math::BigRat, i.e.,
# makes Math::BigInt upgrade to Math::BigRat:
bignum -> upgrade("Math::BigRat");
# The following sets the downgrade class to Math::BigInt::Lite, i.e., makes
# the new upgrade class Math::BigRat downgrade to Math::BigInt::Lite
bignum -> downgrade("Math::BigInt::Lite");
# Note that at this point, it is still Math::BigInt, not Math::BigInt::Lite,
# that upgrades to Math::BigRat, so to get Math::BigInt::Lite to upgrade to
# Math::BigRat, we need to do the following (again):
bignum -> upgrade("Math::BigRat");
A simpler way to do this at runtime is to use import(),
bignum -> import(upgrade => "Math::BigRat",
downgrade => "Math::BigInt::Lite");
Hexadecimal, octal, and binary floating point literals
Perl (and this module) accepts hexadecimal, octal, and binary
floating point literals, but use them with care with Perl versions
before v5.32.0, because some versions of Perl silently give the
wrong result.
Operator vs literal overloading
"bigrat" works by overloading handling of integer and floating point
literals, converting them to Math::BigRat objects.
This means that arithmetic involving only string values or string
literals are performed using Perl's built-in operators.
For example:
use bigrat;
my $x = "900000000000000009";
my $y = "900000000000000007";
print $x - $y;
outputs 0 on default 32-bit builds, since "bignum" never sees the
string literals. To ensure the expression is all treated as
"Math::BigFloat" objects, use a literal number in the expression:
print +(0+$x) - $y;
Ranges
Perl does not allow overloading of ranges, so you can neither safely
use ranges with "bignum" endpoints, nor is the iterator variable a
"Math::BigFloat".
use 5.010;
for my $i (12..13) {
for my $j (20..21) {
say $i ** $j; # produces a floating-point number,
# not an object
}
}
in_effect()
This method only works on Perl v5.9.4 or later.
hex()/oct()
"bignum" overrides 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 bignum":
use bignum qw/hex oct/;
print hex("0x1234567890123456");
{
no bignum;
print hex("0x1234567890123456");
}
The second call to hex() will warn about a non-portable constant.
Compare this to:
use bignum;
# will warn only under Perl older than v5.9.4
print hex("0x1234567890123456");
EXAMPLES
Some cool command line examples to impress the Python crowd ;)
perl -Mbignum -le 'print sqrt(33)'
perl -Mbignum -le 'print 2**255'
perl -Mbignum -le 'print 4.5+2**255'
perl -Mbignum -le 'print 3/7 + 5/7 + 8/3'
perl -Mbignum -le 'print 123->is_odd()'
perl -Mbignum -le 'print log(2)'
perl -Mbignum -le 'print exp(1)'
perl -Mbignum -le 'print 2 ** 0.5'
perl -Mbignum=a,65 -le 'print 2 ** 0.2'
perl -Mbignum=l,GMP -le 'print 7 ** 7777'
BUGS
Please report any bugs or feature requests to "bug-bignum at
rt.cpan.org", or through the web interface at
<https://rt.cpan.org/Ticket/Create.html?Queue=bignum> (requires login).
We will be notified, and then you'll automatically be notified of
progress on your bug as I make changes.
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc bignum
You can also look for information at:
• GitHub
<https://github.com/pjacklam/p5-bignum>
• RT: CPAN's request tracker
<https://rt.cpan.org/Dist/Display.html?Name=bignum>
• MetaCPAN
<https://metacpan.org/release/bignum>
• CPAN Testers Matrix
<http://matrix.cpantesters.org/?dist=bignum>
LICENSE
This program is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.
SEE ALSO
bigint and bigrat.
Math::BigInt, Math::BigFloat, Math::BigRat and Math::Big as well as
Math::BigInt::FastCalc, Math::BigInt::Pari and Math::BigInt::GMP.
AUTHORS
• (C) by Tels <http://bloodgate.com/> in early 2002 - 2007.
• Maintained by Peter John Acklam <pjacklam@gmail.com>, 2014-.
perl v5.40.1 2026-08-30 bignum(3perl)
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