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bigint(3pm)			 Perl Programmers Reference Guide		      bigint(3pm)

NAME
       bigint - Transparent BigInteger support for Perl

SYNOPSIS
	 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";

DESCRIPTION
       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 integer, this pragma creates integer constants that are only limited in their size
       by the available memory and CPU time.

   use integer vs. use bigint
       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"

   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:

       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 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, 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 accuracy at the same time is not possible.

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

       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;".

       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;".

       l, lib, try or only
	 Load a different math lib, see "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 ;)

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

		 perl -Mbigint=v

   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 "lib" warns if none of the specified libraries can be found and Math::BigInt 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.

   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.

   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.

   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.

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

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

       e
		 # 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'.

       PI
		 # 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()
	 Return the class that numbers are upgraded to, is in fact returning
	 $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 LIBRARY
       Math with the numbers is done (by default) by a module called

   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 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.

CAVEATS
       in_effect()
	 This method only works on Perl v5.9.4 or later.

       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");

MODULES USED
       "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

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'

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

SEE ALSO
       Especially bigrat as in "perl -Mbigrat -le 'print 1/3+1/4'" and bignum as in "perl
       -Mbignum -le 'print sqrt(2)'".

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

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

perl v5.16.3				    2013-03-04				      bigint(3pm)
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