bigint - Transparent BigInteger support for Perl |
bigint - Transparent BigInteger support for Perl
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";
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 the integer manpage, this pragma creates integer constants that are only limited in their size by the available memory and CPU time.
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"
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:
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.
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.
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()
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;''.
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 ;)
perl -Mbigint=v
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
the Math::BigInt manpage did fall back to one of the default libraries.
To supress 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.
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 $x->{sign} is not a good idea since there is no guaranty that the object in question has such a hash key, nor is a hash underneath at all.
The sign is either '+', '-', 'NaN', '+inf' or '-inf'.
You can access it with the sign()
method.
A sign of 'NaN' is used to represent the result when input arguments are not numbers or as a result of 0/0. '+inf' and '-inf' represent plus respectively minus infinity. You will get '+inf' when dividing a positive number by 0, and '-inf' when dividing any negative number by 0.
Since all numbers are now objects, you can use all functions that are part of
the BigInt API. You can only use the bxxx()
notation, and not the fxxx()
notation, though.
inf()
inf
properly.
NaN()
NaN
properly.
# perl -Mbigint=e -wle 'print e'
Returns Euler's number e
, aka exp(1). Note that under bigint, this is
truncated to an integer, and hence simple '2'.
# perl -Mbigint=PI -wle 'print PI'
Returns PI. Note that under bigint, this is truncated to an integer, and hence simple '3'.
bexp()
bexp($power,$accuracy);
Returns Euler's number e
raised to the appropriate power, to
the wanted accuracy.
Note that under bigint, the result is truncated to an integer.
Example:
# perl -Mbigint=bexp -wle 'print bexp(1,80)'
bpi()
bpi($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()
$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 bigint
is in effect in the current scope.
This method only works on Perl v5.9.4 or later.
Math with the numbers is done (by default) by a module called
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.
in_effect()
hex()/oct()
bigint
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 bigint'':
use bigint qw/hex oct/;
print hex("0x1234567890123456"); { no bigint; print hex("0x1234567890123456"); }
The second call to hex()
will warn about a non-portable constant.
Compare this to:
use bigint;
# will warn only under Perl older than v5.9.4 print hex("0x1234567890123456");
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
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'
This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.
Especially the bigrat manpage as in perl -Mbigrat -le 'print 1/3+1/4'
and
the bignum manpage as in perl -Mbignum -le 'print sqrt(2)'
.
the Math::BigInt manpage, the Math::BigRat manpage and the Math::Big manpage as well as the Math::BigInt::BitVect manpage, the Math::BigInt::Pari manpage and the Math::BigInt::GMP manpage.
(C) by Tels http://bloodgate.com/ in early 2002 - 2007.
bigint - Transparent BigInteger support for Perl |