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 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 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 $x might be something unexpected. Due to the transparent way of bignum "ref()" should not be necessary, anyway. perl -Mbignum -le 'print +(1234)->copy()->binc()' (Note that print doesn't do what you expect if the expression starts with '(' hence the "+") You can even chain the operations together as usual: perl -Mbignum -le 'print 1234->copy()->binc->badd(6);' 1241 Under bignum (or bigint or bigrat), Perl will "upgrade" the numbers appropriately. This means that: perl -Mbignum -le 'print 1234+4.5' 1238.5 will work correctly. These mixed cases don't do always work when using Math::BigInt or Math::BigFloat alone, or at least not in the way normal Perl scalars work. If you do want to work with large integers like under "use integer;", try "use bigint;": perl -Mbigint -le 'print 1234.5+4.5' 1238 There is also "use bigrat;" which gives you big rationals: perl -Mbigrat -le 'print 1234+4.1' 12381/10 The entire upgrading/downgrading is still experimental and might not work as you expect or may even have bugs. You might get errors like this: Can't use an undefined value as an ARRAY reference at /usr/local/lib/perl5/5.8.0/Math/BigInt/Calc.pm line 864 This means somewhere a routine got a BigFloat/Lite but expected a BigInt (or vice versa) and the upgrade/downgrad path was missing. This is a bug, please report it so that we can fix it. You might consider using just Math::BigInt or Math::BigFloat, since they allow you finer control over what get's done in which module/space. For instance, simple loop counters will be Math::BigInts under "use bignum;" and this is slower than keeping them as Perl scalars: perl -Mbignum -le 'for ($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($_); }' 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's bfround() function for details. perl -Mbignum=p,-50 -le 'printsqrt(20)' 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/Math::BigFloat. 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. $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), " ", $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 the contents works: $x = 9; $y = $x; $z = 9 if $x->is_zero(); # works fine See the documentation about the copy constructor and "=" in overload, as well as the documentation in BigInt for further details. inf() A shortcut to return Math::BigInt->binf(). Useful because Perl does not always handle bareword "inf" properly. NaN() A shortcut to return Math::BigInt->bnan(). Useful because Perl does not always handle bareword "NaN" properly. e # perl -Mbignum=e -wle 'print e' Returns Euler's number "e", akaexp(1). PI() # perl -Mbignum=PI -wle 'print PI' Returns PI. bexp() bexp($power,$accuracy); Returns Euler's number "e" raised to the appropriate power, to the # perl -Mbignum=bpi -wle 'printbpi(80)' upgrade() Return the class that numbers are upgraded to, is in fact returning $Math::BigInt::upgrade. in_effect() use bignum; print "in effect\n" if bignum::in_effect; # true { no bignum; print "in effect\n" if bignum::in_effect; # 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. 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, 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. 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'; 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::BigFLoat. Mixing them together, even with normal scalars is not extraordinary, 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 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 older than v5.9.4 print hex("0x1234567890123456"); MODULES USED "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) Math::BigInt Math::BigFloat EXAMPLES Some cool command line examples to impress the Python crowd ;) perl -Mbignum -le 'printsqrt(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 'printlog(2)' perl -Mbignum -le 'printexp(1)' Math::BigInt::Pari and Math::BigInt::GMP. AUTHORS (C) by Tels <http://bloodgate.com/> in early 2002 - 2007. perl v5.18.2 2014-01-06 bignum(3perl)