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Math::BigFloat(3pm)		 Perl Programmers Reference Guide	      Math::BigFloat(3pm)

NAME
       Math::BigFloat - Arbitrary size floating point math package

SYNOPSIS
	use Math::BigFloat;

	# Number creation
	my $x = Math::BigFloat->new($str);     # defaults to 0
	my $y = $x->copy();		       # make a true copy
	my $nan  = Math::BigFloat->bnan();     # create a NotANumber
	my $zero = Math::BigFloat->bzero();    # create a +0
	my $inf = Math::BigFloat->binf();      # create a +inf
	my $inf = Math::BigFloat->binf('-');   # create a -inf
	my $one = Math::BigFloat->bone();      # create a +1
	my $mone = Math::BigFloat->bone('-');  # create a -1

	my $pi = Math::BigFloat->bpi(100);     # PI to 100 digits

	# the following examples compute their result to 100 digits accuracy:
	my $cos  = Math::BigFloat->new(1)->bcos(100);	     # cosinus(1)
	my $sin  = Math::BigFloat->new(1)->bsin(100);	     # sinus(1)
	my $atan = Math::BigFloat->new(1)->batan(100);	     # arcus tangens(1)

	my $atan2 = Math::BigFloat->new(  1 )->batan2( 1 ,100); # batan(1)
	my $atan2 = Math::BigFloat->new(  1 )->batan2( 8 ,100); # batan(1/8)
	my $atan2 = Math::BigFloat->new( -2 )->batan2( 1 ,100); # batan(-2)

	# Testing
	$x->is_zero();		# true if arg is +0
	$x->is_nan();		# true if arg is NaN
	$x->is_one();		# true if arg is +1
	$x->is_one('-');	# true if arg is -1
	$x->is_odd();		# true if odd, false for even
	$x->is_even();		# true if even, false for odd
	$x->is_pos();		# true if >= 0
	$x->is_neg();		# true if <  0
	$x->is_inf(sign);	# true if +inf, or -inf (default is '+')

	$x->bcmp($y);		# compare numbers (undef,<0,=0,>0)
	$x->bacmp($y);		# compare absolutely (undef,<0,=0,>0)
	$x->sign();		# return the sign, either +,- or NaN
	$x->digit($n);		# return the nth digit, counting from right
	$x->digit(-$n); 	# return the nth digit, counting from left

	# The following all modify their first argument. If you want to pre-
	# serve $x, use $z = $x->copy()->bXXX($y); See under L</CAVEATS> for
	# necessary when mixing $a = $b assignments with non-overloaded math.

	# set
	$x->bzero();		# set $i to 0
	$x->bnan();		# set $i to NaN
	$x->bone();		# set $x to +1
	$x->bone('-');		# set $x to -1
	$x->binf();		# set $x to inf
	$x->binf('-');		# set $x to -inf

	$x->bneg();		# negation
	$x->babs();		# absolute value
	$x->bnorm();		# normalize (no-op)
	$x->bnot();		# two's complement (bit wise not)
	$x->binc();		# increment x by 1
	$x->bdec();		# decrement x by 1

	$x->badd($y);		# addition (add $y to $x)
	$x->bsub($y);		# subtraction (subtract $y from $x)
	$x->bmul($y);		# multiplication (multiply $x by $y)
	$x->bdiv($y);		# divide, set $x to quotient
				# return (quo,rem) or quo if scalar

	$x->bmod($y);		# modulus ($x % $y)
	$x->bpow($y);		# power of arguments ($x ** $y)
	$x->bmodpow($exp,$mod); # modular exponentiation (($num**$exp) % $mod))
	$x->blsft($y, $n);	# left shift by $y places in base $n
	$x->brsft($y, $n);	# right shift by $y places in base $n
				# returns (quo,rem) or quo if in scalar context

	$x->blog();		# logarithm of $x to base e (Euler's number)
	$x->blog($base);	# logarithm of $x to base $base (f.i. 2)
	$x->bexp();		# calculate e ** $x where e is Euler's number

	$x->band($y);		# bit-wise and
	$x->bior($y);		# bit-wise inclusive or
	$x->bxor($y);		# bit-wise exclusive or
	$x->bnot();		# bit-wise not (two's complement)

	$x->bsqrt();		# calculate square-root
	$x->broot($y);		# $y'th root of $x (e.g. $y == 3 => cubic root)
	$x->bfac();		# factorial of $x (1*2*3*4*..$x)

	$x->bround($N); 	# accuracy: preserve $N digits
	$x->bfround($N);	# precision: round to the $Nth digit

	$x->bfloor();		# return integer less or equal than $x
	$x->bceil();		# return integer greater or equal than $x

	 # The following do not modify their arguments:

	bgcd(@values);		# greatest common divisor
	blcm(@values);		# lowest common multiplicator

	$x->bstr();		# return string
	$x->bsstr();		# return string in scientific notation

	$x->as_int();		# return $x as BigInt
	$x->exponent(); 	# return exponent as BigInt
	$x->mantissa(); 	# return mantissa as BigInt
	$x->parts();		# return (mantissa,exponent) as BigInt

	$x->length();		# number of digits (w/o sign and '.')
	($l,$f) = $x->length(); # number of digits, and length of fraction

	$x->precision();	# return P of $x (or global, if P of $x undef)
	$x->precision($n);	# set P of $x to $n
	$x->accuracy(); 	# return A of $x (or global, if A of $x undef)
	$x->accuracy($n);	# set A $x to $n

	# these get/set the appropriate global value for all BigFloat objects
	Math::BigFloat->precision();   # Precision
	Math::BigFloat->accuracy();    # Accuracy
	Math::BigFloat->round_mode();  # rounding mode

DESCRIPTION
       All operators (including basic math operations) are overloaded if you declare your big
       floating point numbers as

	 $i = new Math::BigFloat '12_3.456_789_123_456_789E-2';

       Operations with overloaded operators preserve the arguments, which is exactly what you
       expect.

   Canonical notation
       Input to these routines are either BigFloat objects, or strings of the following four
       forms:

       o "/^[+-]\d+$/"

       o "/^[+-]\d+\.\d*$/"

       o "/^[+-]\d+E[+-]?\d+$/"

       o "/^[+-]\d*\.\d+E[+-]?\d+$/"

       all with optional leading and trailing zeros and/or spaces. Additionally, numbers are
       allowed to have an underscore between any two digits.

       Empty strings as well as other illegal numbers results in 'NaN'.

       bnorm() on a BigFloat object is now effectively a no-op, since the numbers are always
       stored in normalized form. On a string, it creates a BigFloat object.

   Output
       Output values are BigFloat objects (normalized), except for bstr() and bsstr().

       The string output will always have leading and trailing zeros stripped and drop a plus
       sign. "bstr()" will give you always the form with a decimal point, while "bsstr()" (s for
       scientific) gives you the scientific notation.

	       Input		       bstr()	       bsstr()
	       '-0'		       '0'	       '0E1'
	       '  -123 123 123'        '-123123123'    '-123123123E0'
	       '00.0123'	       '0.0123'        '123E-4'
	       '123.45E-2'	       '1.2345'        '12345E-4'
	       '10E+3'		       '10000'	       '1E4'

       Some routines ("is_odd()", "is_even()", "is_zero()", "is_one()", "is_nan()") return true
       or false, while others ("bcmp()", "bacmp()") return either undef, <0, 0 or >0 and are
       suited for sort.

       Actual math is done by using the class defined with "with => Class;" (which defaults to
       BigInts) to represent the mantissa and exponent.

       The sign "/^[+-]$/" is stored separately. The string 'NaN' is used to represent the result
       when input arguments are not numbers, as well as the result of dividing by zero.

   "mantissa()", "exponent()" and "parts()"
       "mantissa()" and "exponent()" return the said parts of the BigFloat as BigInts such that:

	       $m = $x->mantissa();
	       $e = $x->exponent();
	       $y = $m * ( 10 ** $e );
	       print "ok\n" if $x == $y;

       "($m,$e) = $x->parts();" is just a shortcut giving you both of them.

       A zero is represented and returned as 0E1, not 0E0 (after Knuth).

       Currently the mantissa is reduced as much as possible, favouring higher exponents over
       lower ones (e.g. returning 1e7 instead of 10e6 or 10000000e0).  This might change in the
       future, so do not depend on it.

   Accuracy vs. Precision
       See also: Rounding.

       Math::BigFloat supports both precision (rounding to a certain place before or after the
       dot) and accuracy (rounding to a certain number of digits). For a full documentation,
       examples and tips on these topics please see the large section about rounding in
       Math::BigInt.

       Since things like sqrt(2) or "1 / 3" must presented with a limited accuracy lest a
       operation consumes all resources, each operation produces no more than the requested
       number of digits.

       If there is no global precision or accuracy set, and the operation in question was not
       called with a requested precision or accuracy, and the input $x has no accuracy or
       precision set, then a fallback parameter will be used. For historical reasons, it is
       called "div_scale" and can be accessed via:

	       $d = Math::BigFloat->div_scale();       # query
	       Math::BigFloat->div_scale($n);	       # set to $n digits

       The default value for "div_scale" is 40.

       In case the result of one operation has more digits than specified, it is rounded. The
       rounding mode taken is either the default mode, or the one supplied to the operation after
       the scale:

	   $x = Math::BigFloat->new(2);
	   Math::BigFloat->accuracy(5); 	     # 5 digits max
	   $y = $x->copy()->bdiv(3);		     # will give 0.66667
	   $y = $x->copy()->bdiv(3,6);		     # will give 0.666667
	   $y = $x->copy()->bdiv(3,6,undef,'odd');   # will give 0.666667
	   Math::BigFloat->round_mode('zero');
	   $y = $x->copy()->bdiv(3,6);		     # will also give 0.666667

       Note that "Math::BigFloat->accuracy()" and "Math::BigFloat->precision()" set the global
       variables, and thus any newly created number will be subject to the global rounding
       immediately. This means that in the examples above, the 3 as argument to "bdiv()" will
       also get an accuracy of 5.

       It is less confusing to either calculate the result fully, and afterwards round it
       explicitly, or use the additional parameters to the math functions like so:

	       use Math::BigFloat;
	       $x = Math::BigFloat->new(2);
	       $y = $x->copy()->bdiv(3);
	       print $y->bround(5),"\n";	       # will give 0.66667

	       or

	       use Math::BigFloat;
	       $x = Math::BigFloat->new(2);
	       $y = $x->copy()->bdiv(3,5);	       # will give 0.66667
	       print "$y\n";

   Rounding
       ffround ( +$scale )
	 Rounds to the $scale'th place left from the '.', counting from the dot.  The first digit
	 is numbered 1.

       ffround ( -$scale )
	 Rounds to the $scale'th place right from the '.', counting from the dot.

       ffround ( 0 )
	 Rounds to an integer.

       fround  ( +$scale )
	 Preserves accuracy to $scale digits from the left (aka significant digits) and pads the
	 rest with zeros. If the number is between 1 and -1, the significant digits count from
	 the first non-zero after the '.'

       fround  ( -$scale ) and fround ( 0 )
	 These are effectively no-ops.

       All rounding functions take as a second parameter a rounding mode from one of the
       following: 'even', 'odd', '+inf', '-inf', 'zero', 'trunc' or 'common'.

       The default rounding mode is 'even'. By using "Math::BigFloat->round_mode($round_mode);"
       you can get and set the default mode for subsequent rounding. The usage of
       "$Math::BigFloat::$round_mode" is no longer supported.  The second parameter to the round
       functions then overrides the default temporarily.

       The "as_number()" function returns a BigInt from a Math::BigFloat. It uses 'trunc' as
       rounding mode to make it equivalent to:

	       $x = 2.5;
	       $y = int($x) + 2;

       You can override this by passing the desired rounding mode as parameter to "as_number()":

	       $x = Math::BigFloat->new(2.5);
	       $y = $x->as_number('odd');      # $y = 3

METHODS
       Math::BigFloat supports all methods that Math::BigInt supports, except it calculates non-
       integer results when possible. Please see Math::BigInt for a full description of each
       method. Below are just the most important differences:

   accuracy
	       $x->accuracy(5); 	    # local for $x
	       CLASS->accuracy(5);	    # global for all members of CLASS
					    # Note: This also applies to new()!

	       $A = $x->accuracy();	    # read out accuracy that affects $x
	       $A = CLASS->accuracy();	    # read out global accuracy

       Set or get the global or local accuracy, aka how many significant digits the results have.
       If you set a global accuracy, then this also applies to new()!

       Warning! The accuracy sticks, e.g. once you created a number under the influence of
       "CLASS->accuracy($A)", all results from math operations with that number will also be
       rounded.

       In most cases, you should probably round the results explicitly using one of "round()" in
       Math::BigInt, "bround()" in Math::BigInt or "bfround()" in Math::BigInt or by passing the
       desired accuracy to the math operation as additional parameter:

	       my $x = Math::BigInt->new(30000);
	       my $y = Math::BigInt->new(7);
	       print scalar $x->copy()->bdiv($y, 2);	       # print 4300
	       print scalar $x->copy()->bdiv($y)->bround(2);   # print 4300

   precision()
	       $x->precision(-2);      # local for $x, round at the second
				       # digit right of the dot
	       $x->precision(2);       # ditto, round at the second digit left
				       # of the dot

	       CLASS->precision(5);    # Global for all members of CLASS
				       # This also applies to new()!
	       CLASS->precision(-5);   # ditto

	       $P = CLASS->precision();    # read out global precision
	       $P = $x->precision();	   # read out precision that affects $x

       Note: You probably want to use "accuracy" instead. With "accuracy" you set the number of
       digits each result should have, with "precision()" you set the place where to round!

   bexp()
	       $x->bexp($accuracy);	       # calculate e ** X

       Calculates the expression "e ** $x" where "e" is Euler's number.

       This method was added in v1.82 of Math::BigInt (April 2007).

   bnok()
	       $x->bnok($y);   # x over y (binomial coefficient n over k)

       Calculates the binomial coefficient n over k, also called the "choose" function. The
       result is equivalent to:

	       ( n )	  n!
	       | - |  = -------
	       ( k )	k!(n-k)!

       This method was added in v1.84 of Math::BigInt (April 2007).

   bpi()
	       print Math::BigFloat->bpi(100), "\n";

       Calculate PI to N digits (including the 3 before the dot). The result is rounded according
       to the current rounding mode, which defaults to "even".

       This method was added in v1.87 of Math::BigInt (June 2007).

   bcos()
	       my $x = Math::BigFloat->new(1);
	       print $x->bcos(100), "\n";

       Calculate the cosinus of $x, modifying $x in place.

       This method was added in v1.87 of Math::BigInt (June 2007).

   bsin()
	       my $x = Math::BigFloat->new(1);
	       print $x->bsin(100), "\n";

       Calculate the sinus of $x, modifying $x in place.

       This method was added in v1.87 of Math::BigInt (June 2007).

   batan2()
	       my $y = Math::BigFloat->new(2);
	       my $x = Math::BigFloat->new(3);
	       print $y->batan2($x), "\n";

       Calculate the arcus tanges of $y divided by $x, modifying $y in place.  See also
       "batan()".

       This method was added in v1.87 of Math::BigInt (June 2007).

   batan()
	       my $x = Math::BigFloat->new(1);
	       print $x->batan(100), "\n";

       Calculate the arcus tanges of $x, modifying $x in place. See also "batan2()".

       This method was added in v1.87 of Math::BigInt (June 2007).

   bmuladd()
	       $x->bmuladd($y,$z);

       Multiply $x by $y, and then add $z to the result.

       This method was added in v1.87 of Math::BigInt (June 2007).

Autocreating constants
       After "use Math::BigFloat ':constant'" all the floating point constants in the given scope
       are converted to "Math::BigFloat". This conversion happens at compile time.

       In particular

	 perl -MMath::BigFloat=:constant -e 'print 2E-100,"\n"'

       prints the value of "2E-100". Note that without conversion of constants the expression
       2E-100 will be calculated as normal floating point number.

       Please note that ':constant' does not affect integer constants, nor binary nor hexadecimal
       constants. Use bignum or Math::BigInt to get this to work.

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

	       use Math::BigFloat lib => 'Calc';

       You can change this by using:

	       use Math::BigFloat lib => 'GMP';

       Note: General purpose packages should not be explicit about the library to use; let the
       script author decide which is best.

       Note: The keyword 'lib' will warn when the requested library could not be loaded. To
       suppress the warning use 'try' instead:

	       use Math::BigFloat try => 'GMP';

       If your script works with huge numbers and Calc is too slow for them, you can also for the
       loading of one of these libraries and if none of them can be used, the code will die:

	       use Math::BigFloat only => 'GMP,Pari';

       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 Math::BigFloat lib => 'Foo,Math::BigInt::Bar';

       See the respective low-level library documentation for further details.

       Please note that Math::BigFloat does not use the denoted library itself, but it merely
       passes the lib argument to Math::BigInt. So, instead of the need to do:

	       use Math::BigInt lib => 'GMP';
	       use Math::BigFloat;

       you can roll it all into one line:

	       use Math::BigFloat lib => 'GMP';

       It is also possible to just require Math::BigFloat:

	       require Math::BigFloat;

       This will load the necessary things (like BigInt) when they are needed, and automatically.

       See Math::BigInt for more details than you ever wanted to know about using a different
       low-level library.

   Using Math::BigInt::Lite
       For backwards compatibility reasons it is still possible to request a different storage
       class for use with Math::BigFloat:

	       use Math::BigFloat with => 'Math::BigInt::Lite';

       However, this request is ignored, as the current code now uses the low-level math library
       for directly storing the number parts.

EXPORTS
       "Math::BigFloat" exports nothing by default, but can export the "bpi()" method:

	       use Math::BigFloat qw/bpi/;

	       print bpi(10), "\n";

BUGS
       Please see the file BUGS in the CPAN distribution Math::BigInt for known bugs.

CAVEATS
       Do not try to be clever to insert some operations in between switching libraries:

	   require Math::BigFloat;
	   my $matter = Math::BigFloat->bone() + 4;    # load BigInt and Calc
	   Math::BigFloat->import( lib => 'Pari' );    # load Pari, too
	   my $anti_matter = Math::BigFloat->bone()+4; # now use Pari

       This will create objects with numbers stored in two different backend libraries, and VERY
       BAD THINGS will happen when you use these together:

	       my $flash_and_bang = $matter + $anti_matter;    # Don't do this!

       stringify, bstr()
	Both stringify and bstr() now drop the leading '+'. The old code would return '+1.23',
	the new returns '1.23'. See the documentation in Math::BigInt for reasoning and details.

       bdiv
	The following will probably not print what you expect:

		print $c->bdiv(123.456),"\n";

	It prints both quotient and remainder since print works in list context. Also, bdiv()
	will modify $c, so be careful. You probably want to use

	    print $c / 123.456,"\n";
	    print scalar $c->bdiv(123.456),"\n";  # or if you want to modify $c

	instead.

       brsft
	The following will probably not print what you expect:

		my $c = Math::BigFloat->new('3.14159');
		print $c->brsft(3,10),"\n";	# prints 0.00314153.1415

	It prints both quotient and remainder, since print calls "brsft()" in list context. Also,
	"$c->brsft()" will modify $c, so be careful.  You probably want to use

		print scalar $c->copy()->brsft(3,10),"\n";
		# or if you really want to modify $c
		print scalar $c->brsft(3,10),"\n";

	instead.

       Modifying and =
	Beware of:

		$x = Math::BigFloat->new(5);
		$y = $x;

	It will not do what you think, e.g. making a copy of $x. Instead it just makes a second
	reference to the same object and stores it in $y. Thus anything that modifies $x will
	modify $y (except overloaded math operators), and vice versa. See Math::BigInt for
	details and how to avoid that.

       bpow
	"bpow()" now modifies the first argument, unlike the old code which left it alone and
	only returned the result. This is to be consistent with "badd()" etc. The first will
	modify $x, the second one won't:

		print bpow($x,$i),"\n"; 	# modify $x
		print $x->bpow($i),"\n";	# ditto
		print $x ** $i,"\n";		# leave $x alone

       precision() vs. accuracy()
	A common pitfall is to use "precision()" when you want to round a result to a certain
	number of digits:

	    use Math::BigFloat;

	    Math::BigFloat->precision(4);	     # does not do what you
						     # think it does
	    my $x = Math::BigFloat->new(12345);      # rounds $x to "12000"!
	    print "$x\n";			     # print "12000"
	    my $y = Math::BigFloat->new(3);	     # rounds $y to "0"!
	    print "$y\n";			     # print "0"
	    $z = $x / $y;			     # 12000 / 0 => NaN!
	    print "$z\n";
	    print $z->precision(),"\n"; 	     # 4

	Replacing "precision()" with "accuracy" is probably not what you want, either:

	    use Math::BigFloat;

	    Math::BigFloat->accuracy(4);	     # enables global rounding:
	    my $x = Math::BigFloat->new(123456);     # rounded immediately
						     #	 to "12350"
	    print "$x\n";			     # print "123500"
	    my $y = Math::BigFloat->new(3);	     # rounded to "3
	    print "$y\n";			     # print "3"
	    print $z = $x->copy()->bdiv($y),"\n";    # 41170
	    print $z->accuracy(),"\n";		     # 4

	What you want to use instead is:

	    use Math::BigFloat;

	    my $x = Math::BigFloat->new(123456);     # no rounding
	    print "$x\n";			     # print "123456"
	    my $y = Math::BigFloat->new(3);	     # no rounding
	    print "$y\n";			     # print "3"
	    print $z = $x->copy()->bdiv($y,4),"\n";  # 41150
	    print $z->accuracy(),"\n";		     # undef

	In addition to computing what you expected, the last example also does not "taint" the
	result with an accuracy or precision setting, which would influence any further
	operation.

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

       The pragmas bignum, bigint and bigrat might also be of interest because they solve the
       autoupgrading/downgrading issue, at least partly.

       The package at http://search.cpan.org/~tels/Math-BigInt
       <http://search.cpan.org/~tels/Math-BigInt> contains more documentation including a full
       version history, testcases, empty subclass files and benchmarks.

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

AUTHORS
       Mark Biggar, overloaded interface by Ilya Zakharevich.  Completely rewritten by Tels
       <http://bloodgate.com> in 2001 - 2006, and still at it in 2007.

perl v5.16.3				    2013-03-04			      Math::BigFloat(3pm)
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