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Section: User Contributed Perl Documentation (3)
Updated: 2021-10-04


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('0o377');            # from octal  $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('01.3267p-4');  # ditto  $x = Math::BigFloat->from_oct('0o1.3267p-4'); # ditto  $x = Math::BigFloat->from_oct('0377');        # ditto  $x = Math::BigFloat->from_bin('0b1.1001p-4'); # from binary  $x = Math::BigFloat->from_bin('0101');        # ditto  $x = Math::BigFloat->from_ieee754($b, "binary64");  # from IEEE-754 bytes  $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  $x->to_ieee754($format); # to bytes encoded according to IEEE 754-2008  # 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 youdeclare 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 isexactly what you expect. 


Input values to these routines may be any scalar number or string that lookslike a number. Anything that is accepted by Perl as a literal numeric constantshould be accepted by this module.
Leading and trailing whitespace is ignored.
Leading zeros are ignored, except for floating point numbers with a binaryexponent, in which case the number is interpreted as an octal floating pointnumber. For example, ``01.4p+0'' gives 1.5, ``00.4p+0'' gives 0.5, but ``0.4p+0''gives a NaN. And while ``0377'' gives 255, ``0377p0'' gives 255.
If the string has a ``0x'' or ``0X'' prefix, it is interpreted as a hexadecimalnumber.
If the string has a ``0o'' or ``0O'' prefix, it is interpreted as an octal number. Afloating point literal with a ``0'' prefix is also interpreted as an octal number.
If the string has a ``0b'' or ``0B'' prefix, it is interpreted as a binary number.
Underline characters are allowed in the same way as they are allowed in literalnumerical constants.
If the string can not be interpreted, NaN is returned.
For hexadecimal, octal, and binary floating point numbers, the exponent must beseparated from the significand (mantissa) by the letter ``p'' or ``P'', not ``e'' or``E'' as with decimal numbers.

Some examples of valid string input

    Input string                Resulting value    123                         123    1.23e2                      123    12300e-2                    123    67_538_754                  67538754    -4_5_6.7_8_9e+0_1_0         -4567890000000    0x13a                       314    0x13ap0                     314    0x1.3ap+8                   314    0x0.00013ap+24              314    0x13a000p-12                314    0o472                       314    0o1.164p+8                  314    0o0.0001164p+20             314    0o1164000p-10               314    0472                        472     Note!    01.164p+8                   314    00.0001164p+20              314    01164000p-10                314    0b100111010                 314    0b1.0011101p+8              314    0b0.00010011101p+12         314    0b100111010000p-3           314    0x1.921fb5p+1               3.14159262180328369140625e+0    0o1.2677025p1               2.71828174591064453125    01.2677025p1                2.71828174591064453125    0b1.1001p-4                 9.765625e-2


Output values are usually Math::BigFloat objects.

Boolean operators "is_zero()", "is_one()", "is_inf()", etc. return true orfalse.

Comparison operators "bcmp()" and "bacmp()") return -1, 0, 1, orundef. 


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

Configuration methods

    $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 theresults 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 theinfluence of "CLASS->accuracy($A)", all results from math operations withthat 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::BigIntor by passing the desired accuracy to the math operation as additionalparameter:

    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
    $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()'' youset the number of digits each result should have, with ``precision()'' youset the place where to round!


Constructor methods

    $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) isoptional. A single underscore character (``_'') may be placed between any twodigits. If the input is invalid, a NaN is returned. The exponent is in base 2using decimal digits.

If called as an instance method, the value is assigned to the invocand.

    $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 beplaced between any two digits. If the input is invalid, a NaN is returned. Theexponent is in base 2 using decimal digits.

If called as an instance method, the value is assigned to the invocand.

    $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 twodigits. If the input is invalid, a NaN is returned. The exponent is in base 2using decimal digits.

If called as an instance method, the value is assigned to the invocand.

Interpret the input as a value encoded as described in IEEE754-2008. The inputcan be given as a byte string, hex string or binary string. The input isassumed to be in big-endian byte-order.

        # both $dbl and $mbf are 3.141592...        $bytes = "\x40\x09\x21\xfb\x54\x44\x2d\x18";        $dbl = unpack "d>", $bytes;        $mbf = Math::BigFloat -> from_ieee754($bytes, "binary64");
    print Math::BigFloat->bpi(100), "\n";

Calculate PI to N digits (including the 3 before the dot). The result isrounded according to the current rounding mode, which defaults to ``even''.

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


Arithmetic methods


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

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

    $q = $x->bdiv($y);    ($q, $r) = $x->bdiv($y);

In scalar context, divides $x by $y and returns the result to the given ordefault 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)".


Returns $x modulo $y. When $x is finite, and $y is finite and non-zero, theresult 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 resultfrom Perl's % operator.

    $x->bexp($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).

    $x->bnok($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).

    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).

    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).

    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).

    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).

This method is called when Math::BigFloat encounters an object it doesn't knowhow to handle. For instance, assume $x is a Math::BigFloat, or subclassthereof, and $y is defined, but not a Math::BigFloat, or subclass thereof. Ifyou do

    $x -> badd($y);

$y needs to be converted into an object that $x can deal with. This is done byfirst checking if $y is something that $x might be upgraded to. If that is thecase, no further attempts are made. The next is to see if $y supports themethod "as_float()". The method "as_float()" is expected to return either anobject 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()".

Encodes the invocand as a byte string in the given format as specified in IEEE754-2008. Note that the encoded value is the nearest possible representation ofthe value. This value might not be exactly the same as the value in theinvocand.

    # $x = 3.1415926535897932385    $x = Math::BigFloat -> bpi(30);    $b = $x -> to_ieee754("binary64");  # encode as 8 bytes    $h = unpack "H*", $b;               # "400921fb54442d18"    # 3.141592653589793115997963...    $y = Math::BigFloat -> from_ieee754($h, "binary64");

All binary formats in IEEE 754-2008 are accepted. For convenience, som aliasesare recognized: ``half'' for ``binary16'', ``single'' for ``binary32'', ``double'' for``binary64'', ``quadruple'' for ``binary128'', ``octuple'' for ``binary256'', and``sexdecuple'' for ``binary512''.

See also <>.



See also: Rounding.

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

Since things like sqrt(2) or "1 / 3" must presented with a limitedaccuracy lest a operation consumes all resources, each operation producesno more than the requested number of digits.

If there is no global precision or accuracy set, and the operation inquestion was not called with a requested precision or accuracy, and theinput $x has no accuracy or precision set, then a fallback parameter willbe used. For historical reasons, it is called "div_scale" and can be accessedvia:

    $d = Math::BigFloat->div_scale();       # query    Math::BigFloat->div_scale($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 onesupplied 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 subjectto the global rounding immediately. This means that in the examples above, the3 as argument to "bdiv()" will also get an accuracy of 5.

It is less confusing to either calculate the result fully, and afterwardsround it explicitly, or use the additional parameters to the mathfunctions 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";


bfround ( +$scale )
Rounds to the $scale'th place left from the '.', counting from the dot.The first digit is numbered 1.
bfround ( -$scale )
Rounds to the $scale'th place right from the '.', counting from the dot.
bfround ( 0 )
Rounds to an integer.
bround ( +$scale )
Preserves accuracy to $scale digits from the left (aka significant digits) andpads the rest with zeros. If the number is between 1 and -1, the significantdigits count from the first non-zero after the '.'
bround ( -$scale ) and bround ( 0 )
These are effectively no-ops.

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

The default rounding mode is 'even'. By using"Math::BigFloat->round_mode($round_mode);" you can get and set the defaultmode for subsequent rounding. The usage of "$Math::BigFloat::$round_mode" isno longer supported.The second parameter to the round functions then overrides the defaulttemporarily.

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 numeric literals in the given scopeare converted to "Math::BigFloat" objects. This conversion happens at compiletime.

For example,

    perl -MMath::BigFloat=:constant -le 'print 2e-150'

prints the exact value of "2e-150". Note that without conversion of constantsthe expression "2e-150" is calculated using Perl scalars, which leads to aninaccuracte result.

Note that strings are not affected, so that

    use Math::BigFloat qw/:constant/;    $y = "1234567890123456789012345678901234567890"            + "123456789123456789";

does not give you what you expect. You need an explicit Math::BigFloat->new()around at least one of the operands. You should also quote large constants toprevent loss of precision:

    use Math::BigFloat;    $x = Math::BigFloat->new("1234567889123456789123456789123456789");

Without the quotes Perl converts the large number to a floating point constantat compile time, and then converts the result to a Math::BigFloat object atruntime, which results in an inaccurate result. 

Hexadecimal, octal, and binary floating point literals

Perl (and this module) accepts hexadecimal, octal, and binary floating pointliterals, but use them with care with Perl versions before v5.32.0, because someversions of Perl silently give the wrong result. Below are some examples ofdifferent ways to write the number decimal 314.

Hexadecimal floating point literals:

    0x1.3ap+8         0X1.3AP+8    0x1.3ap8          0X1.3AP8    0x13a0p-4         0X13A0P-4

Octal floating point literals (with ``0'' prefix):

    01.164p+8         01.164P+8    01.164p8          01.164P8    011640p-4         011640P-4

Octal floating point literals (with ``0o'' prefix) (requires v5.34.0):

    0o1.164p+8        0O1.164P+8    0o1.164p8         0O1.164P8    0o11640p-4        0O11640P-4

Binary floating point literals:

    0b1.0011101p+8    0B1.0011101P+8    0b1.0011101p8     0B1.0011101P8    0b10011101000p-2  0B10011101000P-2

Math library

Math with the numbers is done (by default) by a module calledMath::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 touse; let the script author decide which is best.

Note: The keyword 'lib' will warn when the requested library could not beloaded. 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 canalso 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.

See Math::BigInt for more details about using a different low-level library. 

Using Math::BigInt::Lite

For backwards compatibility reasons it is still possible torequest 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-levelmath 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 switchinglibraries:

    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 forreasoning and details.
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 listcontext. 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";


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 makesa second reference to the same object and stores it in $y. Thus anythingthat modifies $x will modify $y (except overloaded math operators), and viceversa. See Math::BigInt for details and how to avoid that.

precision() vs. accuracy()
A common pitfall is to use ``precision()'' when you want to round a result toa 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 wouldinfluence any further operation.



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    perldoc Math::BigFloat

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


Math::BigInt and Math::BigInt as well as the backendsMath::BigInt::FastCalc, Math::BigInt::GMP, and Math::BigInt::Pari.

The pragmas bignum, bigint and bigrat. 


Mark Biggar, overloaded interface by Ilya Zakharevich, 1996-2001.
Completely rewritten by Tels <> in 2001-2008.
Florian Ragwitz <>, 2010.
Peter John Acklam <>, 2011-.



Configuration methods
Constructor methods
Arithmetic methods
Hexadecimal, octal, and binary floating point literals
Math library
Using Math::BigInt::Lite

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