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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 v5.10.0 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";


DESCRIPTION

       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 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. 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
         Override the built-in 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.

       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.

   Method calls
       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.

   Methods
       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.


CAVEATS

       Operator vs literal overloading
         "bigint" works by overloading handling of integer and floating point
         literals, converting them to Math::BigInt 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;

       ranges
         Perl does not allow overloading of ranges, so you can neither safely
         use ranges with bigint endpoints, nor is the iterator variable a
         bigint.

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

       Math::BigInt(3), Math::BigRat(3) and Math::Big(3) as well as 
       Math::BigInt::Pari(3) and Math::BigInt::GMP(3).


AUTHORS

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



perl v5.24.0                      2016-03-01                       bigint(3pm)

perl 5.24 - Generated Thu Nov 3 16:24:02 CDT 2016
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