Options¶

"bigfloat" recognizes some options that can be passed while loading it via via "use". The following options exist:

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() method for details.

    perl -Mbigfloat=a,50 -le 'print sqrt(20)'
    

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 means round to integer. See Math::BigInt's bfround() method for details.

    perl -Mbigfloat=p,-50 -le 'print sqrt(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.

l, lib, try, or only

Load a different math lib, see "Math Library".

    perl -Mbigfloat=l,GMP -e 'print 2 ** 512'
    perl -Mbigfloat=lib,GMP -e 'print 2 ** 512'
    perl -Mbigfloat=try,GMP -e 'print 2 ** 512'
    perl -Mbigfloat=only,GMP -e 'print 2 ** 512'
    

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 "bigfloat" 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 "bigfloat" pragma is active.

v or version

this prints out the name and version of the modules and then exits.

    perl -Mbigfloat=v
    

Math Library¶

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

    use bigfloat lib => 'Calc';

you can change this by using:

    use bigfloat lib => 'GMP';

The following would first try to find Math::BigInt::Foo, then Math::BigInt::Bar, and if this also fails, revert to Math::BigInt::Calc:

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

Using c<lib> warns if none of the specified libraries can be found and Math::BigInt fell back to one of the default libraries. To suppress this warning, use c<try> instead:

    use bigfloat try => 'GMP';

If you want the code to die instead of falling back, use "only" instead:

    use bigfloat only => 'GMP';

Please see respective module documentation for further details.

Method calls¶

Since all numbers are now objects, you can use all methods that are part of the Math::BigFloat API.

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 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 that 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 Math::BigFloat for further details.

Methods¶

inf()

A shortcut to return Math::BigFloat->binf(). Useful because Perl does not always handle bareword "inf" properly.

NaN()

A shortcut to return Math::BigFloat->bnan(). Useful because Perl does not always handle bareword "NaN" properly.

e

    # perl -Mbigfloat=e -wle 'print e'
    

Returns Euler's number "e", aka exp(1)

PI

    # perl -Mbigfloat=PI -wle 'print PI'
    

Returns PI.

bexp()

    bexp($power, $accuracy);
    

Returns Euler's number "e" raised to the appropriate power, to the wanted accuracy.

Example:

    # perl -Mbigfloat=bexp -wle 'print bexp(1,80)'
    

bpi()

    bpi($accuracy);
    

Returns PI to the wanted accuracy.

Example:

    # perl -Mbigfloat=bpi -wle 'print bpi(80)'
    

accuracy()

Set or get the accuracy.

precision()

Set or get the precision.

round_mode()

Set or get the rounding mode.

div_scale()

Set or get the division scale.

upgrade()

Set or get the class that the downgrade class upgrades to, if any. Set the upgrade class to "undef" to disable upgrading.

Upgrading is disabled by default.

downgrade()

Set or get the class that the upgrade class downgrades to, if any. Set the downgrade class to "undef" to disable upgrading.

Downgrading is disabled by default.

in_effect()

    use bigfloat;
    print "in effect\n" if bigfloat::in_effect;       # true
    {
        no bigfloat;
        print "in effect\n" if bigfloat::in_effect;   # false
    }
    

Returns true or false if "bigfloat" is in effect in the current scope.

This method only works on Perl v5.9.4 or later.