| 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 v5.10.0 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";
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 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 accuracy 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 accuracy at the same time is not possible.
hex() method with a version that can handle big
integers. 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 bigint pragma is active.
oct() method with a version that can handle big
integers. 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 bigint pragma is active.
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 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.
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.
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 $x->is_zero(); # works fine
See the documentation about the copy constructor and = in overload, as
well as the documentation in BigInt for further details.
inf()inf properly.
NaN()NaN properly.
# perl -Mbigint=e -wle 'print e'
Returns Euler's number e, aka exp(1). Note that under bigint, this is
truncated to an integer, and hence simple '2'.
# perl -Mbigint=PI -wle 'print PI'
Returns PI. Note that under bigint, this is truncated to an integer, and hence simple '3'.
bexp()
bexp($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.
bigint works by overloading handling of integer and floating point
literals, converting them to the Math::BigInt manpage objects.
This means that arithmetic involving only string values or string literals will be performed using Perl's built-in operators.
For example:
use bignum;
my $x = "900000000000000009";
my $y = "900000000000000007";
print $x - $y;
will output 0 on default 32-bit builds, since bigint never sees
the string literals. To ensure the expression is all treated as
Math::BigInt objects, use a literal number in the expression:
print +(0+$x) - $y;
use 5.010;
for my $i (12..13) {
for my $j (20..21) {
say $i ** $j; # produces a floating-point number,
# not a big integer
}
}
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'
For information about bugs and how to report them, see the BUGS section in the documentation available with the perldoc command.
perldoc bignum
You can find documentation for this module with the perldoc command.
perldoc bigint
For more information, see the SUPPORT section in the documentation available with the perldoc command.
perldoc bignum
This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.
the bignum manpage and the bigrat manpage.
the Math::BigInt manpage, the Math::BigFloat manpage, the Math::BigRat manpage and the Math::Big manpage as well as the Math::BigInt::FastCalc manpage, the Math::BigInt::Pari manpage and the Math::BigInt::GMP manpage.
| bigint - Transparent BigInteger support for Perl |