Jarkko Hietaniemi > perl-5.8.1 > bigrat

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Module Version: 0.06   Source  

NAME ^

bigrat - Transparent BigNumber/BigRational support for Perl

SYNOPSIS ^

  use bigrat;

  $x = 2 + 4.5,"\n";                    # BigFloat 6.5
  print 1/3 + 1/4,"\n";                 # produces 7/12

DESCRIPTION ^

All operators (inlcuding basic math operations) are overloaded. Integer and floating-point constants are created as proper BigInts or BigFloats, respectively.

Other than bignum, this module upgrades to Math::BigRat, meaning that instead of 2.5 you will get 2+1/2 as output.

MODULES USED

bigrat 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
        Math::BigRat

MATH LIBRARY

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

        use bigrat lib => 'Calc';

You can change this by using:

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

Please see respective module documentation for further details.

SIGN

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

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 0.

METHODS

Since all numbers are not 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 you independed on the fact that the underlying object might morph into a different class than BigFloat.

CAVEAT

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;

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.

EXAMPLES ^

        perl -Mbigrat -le 'print sqrt(33)'
        perl -Mbigrat -le 'print 2*255'
        perl -Mbigrat -le 'print 4.5+2*255'
        perl -Mbigrat -le 'print 3/7 + 5/7 + 8/3'       
        perl -Mbigrat -le 'print 12->is_odd()';

LICENSE ^

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

SEE ALSO ^

Especially bignum.

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

AUTHORS ^

(C) by Tels http://bloodgate.com/ in early 2002.

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