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

       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 transpar-
       ently 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 con-
       tents 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 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 Big-
       Int/BigFloat on them. This even works to some extent on expressions:

	       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/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 or Math::BigFloat, since they allow you finer
       control over what get's done in which module/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

       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. Nega-
	 tive 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 details.

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

       t or trace
	 This enables a trace mode and is primarily for debugging bignum or Math::Big-

       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 exits.

		 perl -Mbignum=v -e ''


       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.

	   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::Big-


	 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::BigInt::Calc:

		 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, espe-
	 cially 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 nega-
	 tive number by 0.

       "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 <http://bloodgate.com/> in early 2002.

perl v5.8.0				    2002-06-01				      bignum(3pm)
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