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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 accurary 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 accurary 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 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.

       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.

CAVAETS
       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 v5.10.0                                     2007-12-18                                      bigint(3pm)