bigfloat(3perl)  Perl Programmers Reference Guide  bigfloat(3perl) 
NAME¶
bigfloat  transparent big floating point number support for Perl
SYNOPSIS¶
use bigfloat; $x = 2 + 4.5; # Math::BigFloat 6.5 print 2 ** 512 * 0.1; # Math::BigFloat 134...09.6 print inf + 42; # Math::BigFloat inf print NaN * 7; # Math::BigFloat NaN print hex("0x1234567890123490"); # Perl v5.10.0 or later { no bigfloat; print 2 ** 256; # a normal Perl scalar now } # for older Perls, import into current package: use bigfloat qw/hex oct/; print hex("0x1234567890123490"); print oct("01234567890123490");
DESCRIPTION¶
All numeric literals in the given scope are converted to Math::BigFloat objects.
All operators (including basic math operations) except the range operator ".." are overloaded.
So, the following:
use bigfloat; $x = 1234;
creates a Math::BigFloat and stores a reference to in $x. This happens transparently and behind your back, so to speak.
You can see this with the following:
perl Mbigfloat le 'print ref(1234)'
Since numbers are actually objects, you can call all the usual methods from Math::BigFloat on them. This even works to some extent on expressions:
perl Mbigfloat le '$x = 1234; print $x>bdec()' perl Mbigfloat le 'print 1234>copy()>binc();' perl Mbigfloat le 'print 1234>copy()>binc>badd(6);' perl Mbigfloat le 'print +(1234)>copy()>binc()'
(Note that print doesn't do what you expect if the expression starts with '(' hence the "+")
You can even chain the operations together as usual:
perl Mbigfloat le 'print 1234>copy()>binc>badd(6);' 1241
Please note the following does not work as expected (prints nothing), since overloading of '..' is not yet possible in Perl (as of v5.8.0):
perl Mbigfloat le 'for (1..2) { print ref($_); }'
Options¶
"bigfloat" 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 Mbigfloat=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 Mbigfloat=p,50 le 'print sqrt(20)'
Note that setting precision and accuracy at the same time is not possible.
 t or trace
 This enables a trace mode and is primarily for debugging.
 l, lib, try, or only
 Load a different math lib, see "Math Library".
perl Mbigfloat=l,GMP e 'print 2 ** 512' perl Mbigfloat=lib,GMP e 'print 2 ** 512' perl Mbigfloat=try,GMP e 'print 2 ** 512' perl Mbigfloat=only,GMP e 'print 2 ** 512'
 hex
 Override the builtin 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 "bigfloat" pragma is active.
 oct
 Override the builtin 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 "bigfloat" pragma is active.
 v or version
 this prints out the name and version of the modules and then exits.
perl Mbigfloat=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 bigfloat lib => 'Calc';
you can change this by using:
use bigfloat 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 bigfloat lib => 'Foo,Math::BigInt::Bar';
Using c<lib> warns if none of the specified libraries can be found and Math::BigInt fell back to one of the default libraries. To suppress this warning, use c<try> instead:
use bigfloat try => 'GMP';
If you want the code to die instead of falling back, use "only" instead:
use bigfloat only => 'GMP';
Please see respective module documentation for further details.
Method calls¶
Since all numbers are now objects, you can use all methods that are part of the 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 Math::BigFloat>binf(). Useful because Perl does not always handle bareword "inf" properly.
 NaN()
 A shortcut to return Math::BigFloat>bnan(). Useful because Perl does not always handle bareword "NaN" properly.
 e

# perl Mbigfloat=e wle 'print e'
Returns Euler's number "e", aka exp(1)
 PI

# perl Mbigfloat=PI wle 'print PI'
Returns PI.
 bexp()

bexp($power, $accuracy);
Returns Euler's number "e" raised to the appropriate power, to the wanted accuracy.
Example:
# perl Mbigfloat=bexp wle 'print bexp(1,80)'
 bpi()

bpi($accuracy);
Returns PI to the wanted accuracy.
Example:
# perl Mbigfloat=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.
Upgrading is disabled by default.
 downgrade()
 Set or get the class that the upgrade class downgrades to, if any. Set the
downgrade class to "undef" to disable
upgrading.
Downgrading is disabled by default.
 in_effect()

use bigfloat; print "in effect\n" if bigfloat::in_effect; # true { no bigfloat; print "in effect\n" if bigfloat::in_effect; # false }
Returns true or false if "bigfloat" is in effect in the current scope.
This method only works on Perl v5.9.4 or later.
CAVEATS¶
 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 builtin operators.
For example:
use bigrat; my $x = "900000000000000009"; my $y = "900000000000000007"; print $x  $y;
outputs 0 on default 32bit builds, since "bigfloat" never sees the string literals. To ensure the expression is all treated as "Math::BigFloat" objects, use a literal number in the expression:
print +(0+$x)  $y;
 Ranges
 Perl does not allow overloading of ranges, so you can neither safely use
ranges with "bigfloat" 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 floatingpoint number, # not an object } }
 in_effect()
 This method only works on Perl v5.9.4 or later.
 hex()/oct()
 "bigfloat" 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 bigfloat":
use bigfloat qw/hex oct/; print hex("0x1234567890123456"); { no bigfloat; print hex("0x1234567890123456"); }
The second call to hex() will warn about a nonportable constant.
Compare this to:
use bigfloat; # 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 Mbigfloat le 'print sqrt(33)' perl Mbigfloat le 'print 2**255' perl Mbigfloat le 'print 4.5+2**255' perl Mbigfloat le 'print 3/7 + 5/7 + 8/3' perl Mbigfloat le 'print 123>is_odd()' perl Mbigfloat le 'print log(2)' perl Mbigfloat le 'print exp(1)' perl Mbigfloat le 'print 2 ** 0.5' perl Mbigfloat=a,65 le 'print 2 ** 0.2' perl Mbigfloat=l,GMP le 'print 7 ** 7777'
BUGS¶
Please report any bugs or feature requests to "bugbignum 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 bigfloat
You can also look for information at:
 GitHub
 RT: CPAN's request tracker
 MetaCPAN
 CPAN Testers Matrix
 CPAN Ratings
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.
20221018  perl v5.36.0 