| Math::BigFloat - Arbitrary size floating point math package |
Math::BigFloat - Arbitrary size floating point math package
use Math::BigFloat;
# Configuration methods (may be used as class methods and instance methods)
Math::BigFloat->accuracy(); # get class accuracy
Math::BigFloat->accuracy($n); # set class accuracy
Math::BigFloat->precision(); # get class precision
Math::BigFloat->precision($n); # set class precision
Math::BigFloat->round_mode(); # get class rounding mode
Math::BigFloat->round_mode($m); # set global round mode, must be one of
# 'even', 'odd', '+inf', '-inf', 'zero',
# 'trunc', or 'common'
Math::BigFloat->config("lib"); # name of backend math library
# Constructor methods (when the class methods below are used as instance # methods, the value is assigned the invocand)
$x = Math::BigFloat->new($str); # defaults to 0
$x = Math::BigFloat->new('0x123'); # from hexadecimal
$x = Math::BigFloat->new('0b101'); # from binary
$x = Math::BigFloat->from_hex('0xc.afep+3'); # from hex
$x = Math::BigFloat->from_hex('cafe'); # ditto
$x = Math::BigFloat->from_oct('1.3267p-4'); # from octal
$x = Math::BigFloat->from_oct('0377'); # ditto
$x = Math::BigFloat->from_bin('0b1.1001p-4'); # from binary
$x = Math::BigFloat->from_bin('0101'); # ditto
$x = Math::BigFloat->bzero(); # create a +0
$x = Math::BigFloat->bone(); # create a +1
$x = Math::BigFloat->bone('-'); # create a -1
$x = Math::BigFloat->binf(); # create a +inf
$x = Math::BigFloat->binf('-'); # create a -inf
$x = Math::BigFloat->bnan(); # create a Not-A-Number
$x = Math::BigFloat->bpi(); # returns pi
$y = $x->copy(); # make a copy (unlike $y = $x) $y = $x->as_int(); # return as BigInt
# Boolean methods (these don't modify the invocand)
$x->is_zero(); # if $x is 0
$x->is_one(); # if $x is +1
$x->is_one("+"); # ditto
$x->is_one("-"); # if $x is -1
$x->is_inf(); # if $x is +inf or -inf
$x->is_inf("+"); # if $x is +inf
$x->is_inf("-"); # if $x is -inf
$x->is_nan(); # if $x is NaN
$x->is_positive(); # if $x > 0 $x->is_pos(); # ditto $x->is_negative(); # if $x < 0 $x->is_neg(); # ditto
$x->is_odd(); # if $x is odd $x->is_even(); # if $x is even $x->is_int(); # if $x is an integer
# Comparison methods
$x->bcmp($y); # compare numbers (undef, < 0, == 0, > 0) $x->bacmp($y); # compare absolutely (undef, < 0, == 0, > 0) $x->beq($y); # true if and only if $x == $y $x->bne($y); # true if and only if $x != $y $x->blt($y); # true if and only if $x < $y $x->ble($y); # true if and only if $x <= $y $x->bgt($y); # true if and only if $x > $y $x->bge($y); # true if and only if $x >= $y
# Arithmetic methods
$x->bneg(); # negation
$x->babs(); # absolute value
$x->bsgn(); # sign function (-1, 0, 1, or NaN)
$x->bnorm(); # normalize (no-op)
$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)
$x->bmuladd($y,$z); # $x = $x * $y + $z
$x->bdiv($y); # division (floored), set $x to quotient
# return (quo,rem) or quo if scalar
$x->btdiv($y); # division (truncated), set $x to quotient
# return (quo,rem) or quo if scalar
$x->bmod($y); # modulus (x % y)
$x->btmod($y); # modulus (truncated)
$x->bmodinv($mod); # modular multiplicative inverse
$x->bmodpow($y,$mod); # modular exponentiation (($x ** $y) % $mod)
$x->bpow($y); # power of arguments (x ** y)
$x->blog(); # logarithm of $x to base e (Euler's number)
$x->blog($base); # logarithm of $x to base $base (e.g., base 2)
$x->bexp(); # calculate e ** $x where e is Euler's number
$x->bnok($y); # x over y (binomial coefficient n over k)
$x->bsin(); # sine
$x->bcos(); # cosine
$x->batan(); # inverse tangent
$x->batan2($y); # two-argument inverse tangent
$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)
$x->blsft($n); # left shift $n places in base 2
$x->blsft($n,$b); # left shift $n places in base $b
# returns (quo,rem) or quo (scalar context)
$x->brsft($n); # right shift $n places in base 2
$x->brsft($n,$b); # right shift $n places in base $b
# returns (quo,rem) or quo (scalar context)
# Bitwise methods
$x->band($y); # bitwise and $x->bior($y); # bitwise inclusive or $x->bxor($y); # bitwise exclusive or $x->bnot(); # bitwise not (two's complement)
# Rounding methods
$x->round($A,$P,$mode); # round to accuracy or precision using
# rounding mode $mode
$x->bround($n); # accuracy: preserve $n digits
$x->bfround($n); # $n > 0: round to $nth digit left of dec. point
# $n < 0: round to $nth digit right of dec. point
$x->bfloor(); # round towards minus infinity
$x->bceil(); # round towards plus infinity
$x->bint(); # round towards zero
# Other mathematical methods
$x->bgcd($y); # greatest common divisor $x->blcm($y); # least common multiple
# Object property methods (do not modify the invocand)
$x->sign(); # the sign, either +, - or NaN
$x->digit($n); # the nth digit, counting from the right
$x->digit(-$n); # the nth digit, counting from the left
$x->length(); # return number of digits in number
($xl,$f) = $x->length(); # length of number and length of fraction
# part, latter is always 0 digits long
# for Math::BigInt objects
$x->mantissa(); # return (signed) mantissa as BigInt
$x->exponent(); # return exponent as BigInt
$x->parts(); # return (mantissa,exponent) as BigInt
$x->sparts(); # mantissa and exponent (as integers)
$x->nparts(); # mantissa and exponent (normalised)
$x->eparts(); # mantissa and exponent (engineering notation)
$x->dparts(); # integer and fraction part
# Conversion methods (do not modify the invocand)
$x->bstr(); # decimal notation, possibly zero padded $x->bsstr(); # string in scientific notation with integers $x->bnstr(); # string in normalized notation $x->bestr(); # string in engineering notation $x->bdstr(); # string in decimal notation $x->as_hex(); # as signed hexadecimal string with prefixed 0x $x->as_bin(); # as signed binary string with prefixed 0b $x->as_oct(); # as signed octal string with prefixed 0
# Other conversion methods
$x->numify(); # return as scalar (might overflow or underflow)
Math::BigFloat provides support for arbitrary precision floating point. Overloading is also provided for Perl operators.
All operators (including basic math operations) are overloaded if you declare your big floating point numbers as
$x = Math::BigFloat -> new('12_3.456_789_123_456_789E-2');
Operations with overloaded operators preserve the arguments, which is exactly what you expect.
Input values to these routines may be any scalar number or string that looks like a number and represents a floating point number.
Octal numbers are typically prefixed by ``0'', but since leading zeros are
stripped, these methods can not automatically recognize octal numbers, so use
the constructor from_oct() to interpret octal strings.
Some examples of valid string input
Input string Resulting value
123 123
1.23e2 123
12300e-2 123
0xcafe 51966
0b1101 13
67_538_754 67538754
-4_5_6.7_8_9e+0_1_0 -4567890000000
0x1.921fb5p+1 3.14159262180328369140625e+0
0b1.1001p-4 9.765625e-2
Output values are usually Math::BigFloat objects.
Boolean operators is_zero(), is_one(), is_inf(), etc. return true or
false.
Comparison operators bcmp() and bacmp()) return -1, 0, 1, or
undef.
Math::BigFloat supports all methods that Math::BigInt supports, except it calculates non-integer results when possible. Please see the Math::BigInt manpage 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 the Math::BigInt manpage, bround() in the Math::BigInt manpage or bfround() in the Math::BigInt manpage 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!
from_hex()
$x -> from_hex("0x1.921fb54442d18p+1");
$x = Math::BigFloat -> from_hex("0x1.921fb54442d18p+1");
Interpret input as a hexadecimal string.A prefix (``0x'', ``x'', ignoring case) is optional. A single underscore character (``_'') may be placed between any two digits. If the input is invalid, a NaN is returned. The exponent is in base 2 using decimal digits.
If called as an instance method, the value is assigned to the invocand.
from_oct()
$x -> from_oct("1.3267p-4");
$x = Math::BigFloat -> from_oct("1.3267p-4");
Interpret input as an octal string. A single underscore character (``_'') may be placed between any two digits. If the input is invalid, a NaN is returned. The exponent is in base 2 using decimal digits.
If called as an instance method, the value is assigned to the invocand.
from_bin()
$x -> from_bin("0b1.1001p-4");
$x = Math::BigFloat -> from_bin("0b1.1001p-4");
Interpret input as a hexadecimal string. A prefix (``0b'' or ``b'', ignoring case) is optional. A single underscore character (``_'') may be placed between any two digits. If the input is invalid, a NaN is returned. The exponent is in base 2 using decimal digits.
If called as an instance method, the value is assigned to the invocand.
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).
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).
bdiv()
$q = $x->bdiv($y);
($q, $r) = $x->bdiv($y);
In scalar context, divides $x by $y and returns the result to the given or
default accuracy/precision. In list context, does floored division
(F-division), returning an integer $q and a remainder $r so that $x = $q * $y +
$r. The remainer (modulo) is equal to what is returned by $x->bmod($y).
bmod()
$x->bmod($y);
Returns $x modulo $y. When $x is finite, and $y is finite and non-zero, the result is identical to the remainder after floored division (F-division). If, in addition, both $x and $y are integers, the result is identical to the result from Perl's % operator.
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).
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).
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).
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).
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).
as_float()
$x -> badd($y);
$y needs to be converted into an object that $x can deal with. This is done by
first checking if $y is something that $x might be upgraded to. If that is the
case, no further attempts are made. The next is to see if $y supports the
method as_float(). The method as_float() is expected to return either an
object that has the same class as $x, a subclass thereof, or a string that
ref($x)->new() can parse to create an object.
In Math::BigFloat, as_float() has the same effect as copy().
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 the Math::BigInt manpage.
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); # gives 0.66667
$y = $x->copy()->bdiv(3,6); # gives 0.666667
$y = $x->copy()->bdiv(3,6,undef,'odd'); # gives 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"; # gives 0.66667
or
use Math::BigFloat;
$x = Math::BigFloat->new(2);
$y = $x->copy()->bdiv(3,5); # gives 0.66667
print "$y\n";
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
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 the bignum manpage or the Math::BigInt manpage to get this to work.
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 the Math::BigInt manpage for more details than you ever wanted to know about using a different low-level library.
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.
Math::BigFloat exports nothing by default, but can export the bpi() method:
use Math::BigFloat qw/bpi/;
print bpi(10), "\n";
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!
bstr()bstr() now drop the leading '+'. The old code would return
'+1.23', the new returns '1.23'. See the documentation in the Math::BigInt manpage for
reasoning and details.
brsft()
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.
$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 the Math::BigInt manpage for details and how to avoid that.
precision() vs. accuracy()
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.
Please report any bugs or feature requests to
bug-math-bigint at rt.cpan.org, or through the web interface at
https://rt.cpan.org/Ticket/Create.html?Queue=Math-BigInt
(requires login).
We will be notified, and then you'll automatically be notified of progress on
your bug as I make changes.
You can find documentation for this module with the perldoc command.
perldoc Math::BigFloat
You can also look for information at:
bignum at lists.scsys.co.uk
This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.
the Math::BigFloat manpage and the Math::BigInt manpage as well as the backends the Math::BigInt::FastCalc manpage, the Math::BigInt::GMP manpage, and the Math::BigInt::Pari manpage.
The pragmas the bignum manpage, the bigint manpage and the bigrat manpage also might be of interest because they solve the autoupgrading/downgrading issue, at least partly.
| Math::BigFloat - Arbitrary size floating point math package |