# phpman > perldoc > bignum

## NAME
    bignum - Transparent BigNumber support for Perl

## SYNOPSIS
      use bignum;

      $x = 2 + 4.5,"\n";                    # BigFloat 6.5
      print 2 ** 512 * 0.1,"\n";            # really is what you think it is
      print inf * inf,"\n";                 # prints inf
      print NaN * 3,"\n";                   # prints NaN

      {
        no bignum;
        print 2 ** 256,"\n";                # a normal Perl scalar now
      }

      # for older Perls, import into current package:
      use bignum qw/hex oct/;
      print hex("0x1234567890123490"),"\n";
      print oct("01234567890123490"),"\n";

## DESCRIPTION
    All operators (including basic math operations) are overloaded. Integer and floating-point
    constants are created as proper BigInts or BigFloats, respectively.

    If you do

            use bignum;

    at the top of your script, [Math::BigFloat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigFloat/markdown) and [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown) will be loaded and any constant
    number will be converted to an object ([Math::BigFloat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigFloat/markdown) for floats like 3.1415 and [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown)
    for integers like 1234).

    So, the following line:

            $x = 1234;

    creates actually a [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown) and stores a reference to in $x. This happens transparently and
    behind your back, so to speak.

    You can see this with the following:

            perl -Mbignum -le 'print [ref(1234)](https://www.chedong.com/phpMan.php/man/ref/1234/markdown)'

    Don't worry if it says [Math::BigInt::Lite](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3ALite/markdown), bignum and friends will use Lite if it is installed
    since it is faster for some operations. It will be automatically upgraded to BigInt whenever
    necessary:

            perl -Mbignum -le 'print ref(2**255)'

    This also means it is a bad idea to check for some specific package, since the actual contents
    of $x might be something unexpected. Due to the transparent way of bignum "ref()" should not be
    necessary, anyway.

    Since [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown) and BigFloat also overload the normal math operations, the following line
    will still work:

            perl -Mbignum -le 'print ref(1234+1234)'

    Since numbers are actually objects, you can call all the usual methods from BigInt/BigFloat on
    them. This even works to some extent on expressions:

            perl -Mbignum -le '$x = 1234; print $x->bdec()'
            perl -Mbignum -le 'print 1234->copy()->binc();'
            perl -Mbignum -le 'print 1234->copy()->binc->[badd(6)](https://www.chedong.com/phpMan.php/man/badd/6/markdown);'
            perl -Mbignum -le 'print [+(1234)](https://www.chedong.com/phpMan.php/man/%2B/1234/markdown)->copy()->binc()'

    (Note that print doesn't do what you expect if the expression starts with '(' hence the "+")

    You can even chain the operations together as usual:

            perl -Mbignum -le 'print 1234->copy()->binc->[badd(6)](https://www.chedong.com/phpMan.php/man/badd/6/markdown);'
            1241

    Under bignum (or bigint or bigrat), Perl will "upgrade" the numbers appropriately. This means
    that:

            perl -Mbignum -le 'print 1234+4.5'
            1238.5

    will work correctly. These mixed cases don't do always work when using [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown) or
    [Math::BigFloat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigFloat/markdown) alone, or at least not in the way normal Perl scalars work.

    If you do want to work with large integers like under "use integer;", try "use bigint;":

            perl -Mbigint -le 'print 1234.5+4.5'
            1238

    There is also "use bigrat;" which gives you big rationals:

            perl -Mbigrat -le 'print 1234+4.1'
            12381/10

    The entire upgrading/downgrading is still experimental and might not work as you expect or may
    even have bugs. You might get errors like this:

            Can't use an undefined value as an ARRAY reference at
            /usr/local/lib/perl5/5.8.0/Math/BigInt/Calc.pm line 864

    This means somewhere a routine got a BigFloat/Lite but expected a BigInt (or vice versa) and the
    upgrade/downgrad path was missing. This is a bug, please report it so that we can fix it.

    You might consider using just [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown) or [Math::BigFloat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigFloat/markdown), since they allow you finer control
    over what get's done in which module/space. For instance, simple loop counters will be
    [Math::BigInts](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInts/markdown) under "use bignum;" and this is slower than keeping them as Perl scalars:

        perl -Mbignum -le 'for ($i = 0; $i < 10; $i++) { print ref($i); }'

    Please note the following does not work as expected (prints nothing), since overloading of '..'
    is not yet possible in Perl (as of v5.8.0):

        perl -Mbignum -le 'for (1..2) { print ref($_); }'

### Options
    bignum 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](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown)'s bround() function for details.

              perl -Mbignum=a,50 -le 'print [sqrt(20)](https://www.chedong.com/phpMan.php/man/sqrt/20/markdown)'

      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, while a positive value rounds to this
      digit left from the dot. 0 or 1 mean round to integer. See [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown)'s bfround() function
      for details.

              perl -Mbignum=p,-50 -le 'print [sqrt(20)](https://www.chedong.com/phpMan.php/man/sqrt/20/markdown)'

      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 bignum or
      [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown)/[Math::BigFloat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigFloat/markdown).

    l or lib
      Load a different math lib, see "Math Library".

              perl -Mbignum=l,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 ;)

    hex
      Override the built-in hex() method with a version that can handle big numbers. 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 bignum pragma is
      active.

    oct
      Override the built-in oct() method with a version that can handle big numbers. 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.

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

              perl -Mbignum=v

### Methods
    Beside import() and AUTOLOAD() there are only a few other methods.

    Since all numbers are now objects, you can use all functions that are part of the BigInt or
    BigFloat API. It is wise to use only the bxxx() notation, and not the fxxx() notation, though.
    This makes it possible that the underlying object might morph into a different class than
    BigFloat.

### Caveats
    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;

    If you want to make a real copy, use the following:

            $y = $x->copy();

    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)](https://www.chedong.com/phpMan.php/man/badd/1/markdown), " ", $y,"\n";        # prints 10 10

            $x = 9; $y = $x;
            print $x->[binc(1)](https://www.chedong.com/phpMan.php/man/binc/1/markdown), " ", $y,"\n";        # prints 10 10

            $x = 9; $y = $x;
            print $x->[bmul(2)](https://www.chedong.com/phpMan.php/man/bmul/2/markdown), " ", $y,"\n";        # prints 18 18

    Using methods that do not modify, but test 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
      A shortcut to return [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown)->binf(). Useful because Perl does not always handle bareword
      "inf" properly.

    NaN()
      A shortcut to return [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown)->bnan(). Useful because Perl does not always handle bareword
      "NaN" properly.

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

      Returns Euler's number "e", aka [exp(1)](https://www.chedong.com/phpMan.php/man/exp/1/markdown).

    PI()
              # perl -Mbignum=PI -wle 'print PI'

      Returns PI.

### bexp
              bexp($power,$accuracy);

      Returns Euler's number "e" raised to the appropriate power, to the wanted accuracy.

      Example:

              # perl -Mbignum=bexp -wle 'print bexp(1,80)'

### bpi
              bpi($accuracy);

      Returns PI to the wanted accuracy.

      Example:

              # perl -Mbignum=bpi -wle 'print [bpi(80)](https://www.chedong.com/phpMan.php/man/bpi/80/markdown)'

### upgrade
      Return the class that numbers are upgraded to, is in fact returning $[Math::BigInt::upgrade](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3Aupgrade/markdown).

### in_effect
              use bignum;

              print "in effect\n" if [bignum::in_effect](https://www.chedong.com/phpMan.php/perldoc/bignum%3A%3Aineffect/markdown);       # true
              {
                no bignum;
                print "in effect\n" if [bignum::in_effect](https://www.chedong.com/phpMan.php/perldoc/bignum%3A%3Aineffect/markdown);     # false
              }

      Returns true or false if "bignum" 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 [Math::BigInt::Calc](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3ACalc/markdown). This is
    equivalent to saying:

            use bignum lib => 'Calc';

    You can change this by using:

            use bignum lib => 'GMP';

    The following would first try to find [Math::BigInt::Foo](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3AFoo/markdown), then [Math::BigInt::Bar](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3ABar/markdown), and when this
    also fails, revert to [Math::BigInt::Calc](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3ACalc/markdown):

            use bignum lib => 'Foo,[Math::BigInt::Bar](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3ABar/markdown)';

    Please see respective module documentation for further details.

    Using "lib" warns if none of the specified libraries can be found and [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown) 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';

  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](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown),
    or [Math::BigFloat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigFloat/markdown). 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 bright idea since there is no guaranty that the object in
    question has such a hashkey, nor is a hash underneath at all.

  SIGN
    The sign is either '+', '-', 'NaN', '+inf' or '-inf' and stored separately. 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.

## CAVEATS
    Operator vs literal overloading
      "bignum" works by overloading handling of integer and floating point literals, converting them
      to [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown) or [Math::BigFloat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigFloat/markdown) 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 "bigrat" never sees the string literals. To
      ensure the expression is all treated as "[Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown)" or "BigFloat" objects, use a literal
      number in the expression:

          print +(0+$x) - $y;

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

### hex
      "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 older than v5.9.4
              print hex("0x1234567890123456");

## MODULES USED
    "bignum" is just a thin wrapper around various modules of the [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown) 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 bignum:

            [Math::BigInt::Lite](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3ALite/markdown)      (for speed, and only if it is loadable)
            [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown)
            [Math::BigFloat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigFloat/markdown)

## EXAMPLES
    Some cool command line examples to impress the Python crowd ;)

            perl -Mbignum -le 'print [sqrt(33)](https://www.chedong.com/phpMan.php/man/sqrt/33/markdown)'
            perl -Mbignum -le 'print 2*255'
            perl -Mbignum -le 'print 4.5+2*255'
            perl -Mbignum -le 'print 3/7 + 5/7 + 8/3'
            perl -Mbignum -le 'print 123->is_odd()'
            perl -Mbignum -le 'print [log(2)](https://www.chedong.com/phpMan.php/man/log/2/markdown)'
            perl -Mbignum -le 'print [exp(1)](https://www.chedong.com/phpMan.php/man/exp/1/markdown)'
            perl -Mbignum -le 'print 2 ** 0.5'
            perl -Mbignum=a,65 -le 'print 2 ** 0.2'
            perl -Mbignum=a,65,l,GMP -le 'print 7 ** 7777'

## BUGS
    Please report any bugs or feature requests to "bug-math-bigint at rt.cpan.org", or through the
    web interface at <<https://rt.cpan.org/Ticket/Create.html?Queue=bignum>> (requires login). We will
    be notified, and then you'll automatically be notified of progress on your bug as I make
    changes.

## SUPPORT
    You can find documentation for this module with the perldoc command.

        perldoc bignum

    You can also look for information at:

    *   RT: CPAN's request tracker

        <<https://rt.cpan.org/Public/Dist/Display.html?Name=bignum>>

    *   AnnoCPAN: Annotated CPAN documentation

        <<http://annocpan.org/dist/bignum>>

    *   CPAN Ratings

        <<http://cpanratings.perl.org/dist/bignum>>

    *   Search CPAN

        <<http://search.cpan.org/dist/bignum/>>

    *   CPAN Testers Matrix

        <<http://matrix.cpantesters.org/?dist=bignum>>

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

## SEE ALSO
    bigint and bigrat.

    [Math::BigInt](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt/markdown), [Math::BigFloat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigFloat/markdown), [Math::BigRat](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigRat/markdown) and [Math::Big](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABig/markdown) as well as [Math::BigInt::FastCalc](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3AFastCalc/markdown),
    [Math::BigInt::Pari](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3APari/markdown) and [Math::BigInt::GMP](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ABigInt%3A%3AGMP/markdown).

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

    *   Maintained by Peter John Acklam <<pjacklam@gmail.com><gt>, 2014-.