bigint.pm

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	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 B<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"

=head2 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:

=over 2

=item 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.

=item 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.

=item t or trace

This enables a trace mode and is primarily for debugging bigint or
Math::BigInt.

=item hex

Override the built-in 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;".

=item oct

Override the built-in 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;".

=item l, lib, try or only

Load a different math lib, see L<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 ;)

=item v or version

This prints out the name and version of all modules used and then exits.

	perl -Mbigint=v

=back

=head2 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 C<lib> warns if none of the specified libraries can be found and
L<Math::BigInt> did fall back to one of the default libraries.
To supress this warning, use C<try> instead:

        use bignum try => 'GMP';

If you want the code to die instead of falling back, use C<only> instead:

        use bignum only => 'GMP';

Please see respective module documentation for further details.

=head2 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.

=head2 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.

=head2 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. 

=over 2

=item inf()

A shortcut to return Math::BigInt->binf(). Useful because Perl does not always
handle bareword C<inf> properly.

=item NaN()

A shortcut to return Math::BigInt->bnan(). Useful because Perl does not always
handle bareword C<NaN> properly.

=item e

	# perl -Mbigint=e -wle 'print e'

Returns Euler's number C<e>, aka exp(1). Note that under bigint, this is
truncated to an integer, and hence simple '2'.

=item PI

	# perl -Mbigint=PI -wle 'print PI'

Returns PI. Note that under bigint, this is truncated to an integer, and hence
simple '3'.

=item bexp()

	bexp($power,$accuracy);

Returns Euler's number C<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)'

=item 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)'

=item upgrade()

Return the class that numbers are upgraded to, is in fact returning
C<$Math::BigInt::upgrade>.

=item 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 C<bigint> is in effect in the current scope.

This method only works on Perl v5.9.4 or later.

=back

=head2 MATH LIBRARY

Math with the numbers is done (by default) by a module called

=head2 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
B<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 C<=> in overload, as
well as the documentation in BigInt for further details.

=head1 CAVAETS

=over 2

=item in_effect()

This method only works on Perl v5.9.4 or later.

=item hex()/oct()

C<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");

=back

=head1 MODULES USED

C<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

=head1 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'

=head1 LICENSE

This program is free software; you may redistribute it and/or modify it under
the same terms as Perl itself.

=head1 SEE ALSO

Especially L<bigrat> as in C<perl -Mbigrat -le 'print 1/3+1/4'> and
L<bignum> as in C<perl -Mbignum -le 'print sqrt(2)'>.

L<Math::BigInt>, L<Math::BigRat> and L<Math::Big> as well
as L<Math::BigInt::BitVect>, L<Math::BigInt::Pari> and  L<Math::BigInt::GMP>.

=head1 AUTHORS

(C) by Tels L<http://bloodgate.com/> in early 2002 - 2007.

=cut