NAME

Math::BigInt::Calc - Pure Perl module to support Math::BigInt

SYNOPSIS

Provides support for big integer calculations. Not intended to be used by other modules. Other modules which export the same functions can also be used to support Math::Bigint

DESCRIPTION

In order to allow for multiple big integer libraries, Math::BigInt was rewritten to use library modules for core math routines. Any module which follows the same API as this can be used instead by using the following call:

use Math::BigInt lib => BigNum;

EXPORT

The following functions MUST be exported in order to support the use by Math::BigInt:

	_new(string)	return ref to new object from ref to decimal string
	_zero()		return a new object with value 0
	_one()		return a new object with value 1

	_str(obj)	return ref to a string representing the object
	_num(obj)	returns a Perl integer/floating point number
			NOTE: because of Perl numeric notation defaults,
			the _num'ified obj may lose accuracy due to 
			machine-dependend floating point size limitations
                    
	_add(obj,obj)	Simple addition of two objects
	_mul(obj,obj)	Multiplication of two objects
	_div(obj,obj)	Division of the 1st object by the 2nd
			In list context, returns (result,remainder).
			NOTE: this is integer math, so no
			fractional part will be returned.
	_sub(obj,obj)	Simple subtraction of 1 object from another
			a third, optional parameter indicates that the params
			are swapped. In this case, the first param needs to
			be preserved, while you can destroy the second.
			sub (x,y,1) => return x - y and keep x intact!

	_acmp(obj,obj)	<=> operator for objects (return -1, 0 or 1)

	_len(obj)	returns count of the decimal digits of the object
	_digit(obj,n)	returns the n'th decimal digit of object

	_is_one(obj)	return true if argument is +1
	_is_zero(obj)	return true if argument is 0
	_is_even(obj)	return true if argument is even (0,2,4,6..)
	_is_odd(obj)	return true if argument is odd (1,3,5,7..)

	_copy		return a ref to a true copy of the object

	_check(obj)	check whether internal representation is still intact
			return 0 for ok, otherwise error message as string

The following functions are optional, and can be exported if the underlying lib has a fast way to do them. If not defined, Math::BigInt will use a pure, but slow, Perl function as fallback to emulate these:

_from_hex(str)	return ref to new object from ref to hexadecimal string
_from_bin(str)	return ref to new object from ref to binary string

_rsft(obj,N,B)	shift object in base B by N 'digits' right
_lsft(obj,N,B)	shift object in base B by N 'digits' left

_xor(obj1,obj2)	XOR (bit-wise) object 1 with object 2
		Mote: XOR, AND and OR pad with zeros if size mismatches
_and(obj1,obj2)	AND (bit-wise) object 1 with object 2
_or(obj1,obj2)	OR (bit-wise) object 1 with object 2

_sqrt(obj)	return the square root of object
_pow(obj,obj)	return object 1 to the power of object 2
_gcd(obj,obj)	return Greatest Common Divisor of two objects

_zeros(obj)	return number of trailing decimal zeros

_dec(obj)	decrement object by one (input is >= 1)
_inc(obj)	increment object by one

Input strings come in as unsigned but with prefix (i.e. as '123', '0xabc' or '0b1101').

Testing of input parameter validity is done by the caller, so you need not worry about underflow (f.i. in _sub(), _dec()) nor about division by zero or similar cases.

The first parameter can be modified, that includes the possibility that you return a reference to a completely different object instead. Although keeping the reference the same is prefered.

Return values are always references to objects or strings. Exceptions are _lsft() and _rsft(), which return undef if they can not shift the argument. This is used to delegate shifting of bases different than 10 back to BigInt, which will use some generic code to calculate the result.

WRAP YOUR OWN

If you want to port your own favourite c-lib for big numbers to the Math::BigInt interface, you can take any of the already existing modules as a rough guideline. You should really wrap up the latest BigInt and BigFloat testsuites with your module, and replace the following line:

use Math::BigInt;

by

use Math::BigInt lib => 'yourlib';

This way you ensure that your library really works 100% within Math::BigInt.

LICENSE

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

AUTHORS

Original math code by Mark Biggar, rewritten by Tels http://bloodgate.com/ in late 2000, 2001. Seperated from BigInt and shaped API with the help of John Peacock.

SEE ALSO

Math::BigInt, Math::BigFloat, Math::BigInt::BitVect and Math::BigInt::Pari.