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bignum(3)	       Perl Programmers Reference Guide		     bignum(3)

       bignum - Transparent BigNumber support for Perl

	 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

       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 and Math::BigInt will be
       loaded and any constant number will be converted to an object
       (Math::BigFloat for floats like 3.1415 and Math::BigInt for integers
       like 1234).

       So, the following line:

	       $x = 1234;

       creates actually a Math::BigInt 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)'

       Don't worry if it says Math::BigInt::Lite, 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 neccessary:

	       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 neccessary, anyway.

       Since Math::BigInt and BigFloat also overload the normal math opera‐
       tions, 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 expres‐

	       perl -Mbignum -le '$x = 1234; print $x->bdec()'
	       perl -Mbignum -le 'print 1234->binc();'
	       perl -Mbignum -le 'print 1234->binc->badd(6);'
	       perl -Mbignum -le 'print +(1234)->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->binc->badd(6);'

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

	       perl -Mbignum -le 'print 1234+4.5'

       will work correctly. These mixed cases don't do always work when using
       Math::BigInt or Math::BigFloat 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'

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

	       perl -Mbigrat -le 'print 1234+4.1'

       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/ line 864

       This means somewhere a routine got a BigFloat/Lite but expected a Big‐
       Int (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 or Math::BigFloat, since
       they allow you finer control over what get's done in which mod‐
       ule/space. For instance, simple loop counters will be Math::BigInts
       under "use bignum;" and this is slower than keeping them as Perl

	       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($_); }'


       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's bround() function
	 for details.

		 perl -Mbignum=a,50 -le 'print sqrt(20)'

       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's bfround() function for

		 perl -Mbignum=p,-50 -le 'print sqrt(20)'

       t or trace
	 This enables a trace mode and is primarily for debugging bignum or

       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 will be hopefully fixed soon ;)

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

		 perl -Mbignum=v


       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


       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 beeing 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.

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

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

	   Return the class that numbers are upgraded to, is in fact returning


	 Math with the numbers is done (by default) by a module called
	 Math::BigInt::Calc. This is equivalent to saying:

		 use bignum lib => 'Calc';

	 You can change this by using:

		 use bignum lib => 'BitVect';

	 The following would first try to find Math::BigInt::Foo, then
	 Math::BigInt::Bar, and when this also fails, revert to Math::Big‐

		 use bignum lib => 'Foo,Math::BigInt::Bar';

	 Please see respective module documentation for further details.


	 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::BigFLoat. 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.


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

       "bignum" 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 bignum:

	       Math::BigInt::Lite      (for speed, and only if it is loadable)

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

	       perl -Mbignum -le 'print sqrt(33)'
	       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)'
	       perl -Mbignum -le 'print 2 ** 0.5'
	       perl -Mbignum=a,65 -le 'print 2 ** 0.2'

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

       Especially bigrat as in "perl -Mbigrat -le 'print 1/3+1/4'".

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

       (C) by Tels <> in early 2002, 2003.

perl v5.8.8			  2004-05-07			     bignum(3)
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