Math::BigInt::Calc(3)

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 sport the same functions can also be used to support Math::BigInt, like Math::BigInt::GMP or Math::BigInt::Pari.

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:

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

'libname' is either the long name ('Math::BigInt::Pari'), or only the short version like 'Pari'.

STORAGE

METHODS
The following functions MUST be defined in order to support the use by Math::BigInt v1.70 or later:

        api_version()   return API version, 1 for v1.70, 2 for v1.83
        _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
        _two()          return a new object with value 2
        _ten()          return a new object with value 10

        _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-dependent 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.
                        The second operand will be not be 0, so no need to
                        check for that.
        _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!
        _dec(obj)       decrement object by one (input is guaranteed to be > 0)
        _inc(obj)       increment object by one

        _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_two(obj)    return true if argument is 2
        _is_ten(obj)    return true if argument is 10
        _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

        _from_hex(str)  return new object from a hexadecimal string
        _from_bin(str)  return new object from a binary string
        _from_oct(str)  return new object from an octal string

        _as_hex(str)    return string containing the value as
                        unsigned hex string, with the '0x' prepended.
                        Leading zeros must be stripped.
        _as_bin(str)    Like as_hex, only as binary string containing only
                        zeros and ones. Leading zeros must be stripped and a
                        '0b' must be prepended.

        _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
                        Note: 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

        _mod(obj1,obj2) Return remainder of div of the 1st by the 2nd object
        _sqrt(obj)      return the square root of object (truncated to int)
        _root(obj)      return the n'th (n >= 3) root of obj (truncated to int)
        _fac(obj)       return factorial of object 1 (1*2*3*4..)
        _pow(obj1,obj2) return object 1 to the power of object 2
                        return undef for NaN
        _zeros(obj)     return number of trailing decimal zeros
        _modinv         return inverse modulus
        _modpow         return modulus of power ($x ** $y) % $z
        _log_int(X,N)   calculate integer log() of X in base N
                        X >= 0, N >= 0 (return undef for NaN)
                        returns (RESULT, EXACT) where EXACT is:
                         1     : result is exactly RESULT
                         0     : result was truncated to RESULT
                         undef : unknown whether result is exactly RESULT
        _gcd(obj,obj)   return Greatest Common Divisor of two objects

The following functions are REQUIRED for an api_version of 2 or greater:

        _1ex($x)        create the number 1Ex where x >= 0
        _alen(obj)      returns approximate count of the decimal digits of the
                        object. This estimate MUST always be greater or equal
                        to what _len() returns.
        _nok(n,k)       calculate n over k (binomial coefficient)

The following functions are optional, and can be defined if the underlying lib has a fast way to do them. If undefined, Math::BigInt will use pure Perl (hence slow) fallback routines to emulate these:

        _signed_or
        _signed_and
        _signed_xor

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

So the library needs only to deal with unsigned big integers. 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 and just changing its contents is preferred over creating and returning a different reference.

Return values are always references to objects, strings, or true/false for comparison routines.

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 in them any of the following:

        use Math::BigInt;

by this:

        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. Seperated from BigInt and shaped API with the help of John Peacock.

Fixed, speed-up, streamlined and enhanced by Tels 2001 - 2007.

SEE ALSO
Math::BigInt, Math::BigFloat, Math::BigInt::GMP, Math::BigInt::FastCalc and Math::BigInt::Pari.