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Math::BigInt(3p) Perl Programmers Reference GuideMath::BigInt(3p)


NAME
       Math::BigInt - Arbitrary size integer math package

SYNOPSIS
         use Math::BigInt;

         # or make it faster: install (optional) Math::BigInt::GMP
         # and always use (it will fall back to pure Perl if the
         # GMP library is not installed):

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

         my $str = '1234567890';
         my @values = (64,74,18);
         my $n = 1; my $sign = '-';

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

         # Testing (don't modify their arguments)
         # (return true if the condition is met, otherwise false)

         $x->is_zero();        # if $x is +0
         $x->is_nan();         # if $x is NaN
         $x->is_one();         # if $x is +1
         $x->is_one('-');      # if $x is -1
         $x->is_odd();         # if $x is odd
         $x->is_even();        # if $x is even
         $x->is_pos();         # if $x >= 0
         $x->is_neg();         # if $x <  0
         $x->is_inf($sign);    # if $x is +inf, or -inf (sign is default '+')
         $x->is_int();         # if $x is an integer (not a float)

         # comparing and digit/sign extration
         $x->bcmp($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 preserve
         # $x, use $z = $x->copy()->bXXX($y); See under L<CAVEATS> for why this is
         # neccessary when mixing $a = $b assigments with non-overloaded math.







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Math::BigInt(3p) Perl Programmers Reference GuideMath::BigInt(3p)


         $x->bzero();          # set $x to 0
         $x->bnan();           # set $x 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 in BigInt)
         $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)
         $x->bmodpow($exp,$mod);  # modular exponentation (($num**$exp) % $mod))
         $x->bmodinv($mod);       # the inverse of $x in the given modulus $mod

         $x->bpow($y);            # power of arguments (x ** y)
         $x->blsft($y);           # left shift
         $x->brsft($y);           # right shift
         $x->blsft($y,$n);        # left shift, by base $n (like 10)
         $x->brsft($y,$n);        # right shift, by base $n (like 10)

         $x->band($y);            # bitwise and
         $x->bior($y);            # bitwise inclusive or
         $x->bxor($y);            # bitwise exclusive or
         $x->bnot();              # bitwise 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)

         $x->round($A,$P,$mode);  # round to accuracy or precision using mode $mode
         $x->bround($n);          # accuracy: preserve $n digits
         $x->bfround($n);         # round to $nth digit, no-op for BigInts

         # The following do not modify their arguments in BigInt (are no-ops),
         # but do so in BigFloat:

         $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:







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Math::BigInt(3p) Perl Programmers Reference GuideMath::BigInt(3p)


         # greatest common divisor (no OO style)
         my $gcd = Math::BigInt::bgcd(@values);
         # lowest common multiplicator (no OO style)
         my $lcm = Math::BigInt::blcm(@values);

         $x->length();            # return number of digits in number
         ($xl,$f) = $x->length(); # length of number and length of fraction part,
                                  # latter is always 0 digits long for BigInt's

         $x->exponent();          # return exponent as BigInt
         $x->mantissa();          # return (signed) mantissa as BigInt
         $x->parts();             # return (mantissa,exponent) as BigInt
         $x->copy();              # make a true copy of $x (unlike $y = $x;)
         $x->as_int();            # return as BigInt (in BigInt: same as copy())
         $x->numify();            # return as scalar (might overflow!)

         # conversation to string (do not modify their argument)
         $x->bstr();              # normalized string
         $x->bsstr();             # normalized string in scientific notation
         $x->as_hex();            # as signed hexadecimal string with prefixed 0x
         $x->as_bin();            # as signed binary string with prefixed 0b

         # precision and accuracy (see section about rounding for more)
         $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

         # Global methods
         Math::BigInt->precision(); # get/set global P for all BigInt objects
         Math::BigInt->accuracy();  # get/set global A for all BigInt objects
         Math::BigInt->config();    # return hash containing configuration

DESCRIPTION
       All operators (inlcuding basic math operations) are over-
       loaded if you declare your big integers as

         $i = new Math::BigInt '123_456_789_123_456_789';

       Operations with overloaded operators preserve the argu-
       ments which is exactly what you expect.

       Input
         Input values to these routines may be any string, that
         looks like a number and results in an integer, including
         hexadecimal and binary numbers.

         Scalars holding numbers may also be passed, but note
         that non-integer numbers may already have lost precision
         due to the conversation to float. Quote your input if
         you want BigInt to see all the digits:

                 $x = Math::BigInt->new(12345678890123456789);   # bad
                 $x = Math::BigInt->new('12345678901234567890'); # good



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         You can include one underscore between any two digits.

         This means integer values like 1.01E2 or even 1000E-2
         are also accepted.  Non-integer values result in NaN.

         Currently, Math::BigInt::new() defaults to 0, while
         Math::BigInt::new('') results in 'NaN'. This might
         change in the future, so use always the following
         explicit forms to get a zero or NaN:

                 $zero = Math::BigInt->bzero();
                 $nan = Math::BigInt->bnan();

         "bnorm()" on a BigInt object is now effectively a no-op,
         since the numbers are always stored in normalized form.
         If passed a string, creates a BigInt object from the
         input.

       Output
         Output values are BigInt objects (normalized), except
         for bstr(), which returns a string in normalized form.
         Some routines ("is_odd()", "is_even()", "is_zero()",
         "is_one()", "is_nan()") return true or false, while oth-
         ers ("bcmp()", "bacmp()") return either undef, <0, 0 or
         >0 and are suited for sort.

METHODS
       Each of the methods below (except config(), accuracy() and
       precision()) accepts three additional parameters. These
       arguments $A, $P and $R are accuracy, precision and
       round_mode. Please see the section about "ACCURACY and
       PRECISION" for more information.

       config

               use Data::Dumper;

               print Dumper ( Math::BigInt->config() );
               print Math::BigInt->config()->{lib},"\n";

       Returns a hash containing the configuration, e.g. the ver-
       sion number, lib loaded etc. The following hash keys are
       currently filled in with the appropriate information.














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               key             Description
                               Example
               ============================================================
               lib             Name of the low-level math library
                               Math::BigInt::Calc
               lib_version     Version of low-level math library (see 'lib')
                               0.30
               class           The class name of config() you just called
                               Math::BigInt
               upgrade         To which class math operations might be upgraded
                               Math::BigFloat
               downgrade       To which class math operations might be downgraded
                               undef
               precision       Global precision
                               undef
               accuracy        Global accuracy
                               undef
               round_mode      Global round mode
                               even
               version         version number of the class you used
                               1.61
               div_scale       Fallback acccuracy for div
                               40
               trap_nan        If true, traps creation of NaN via croak()
                               1
               trap_inf        If true, traps creation of +inf/-inf via croak()
                               1

       The following values can be set by passing "config()" a
       reference to a hash:

               trap_inf trap_nan
               upgrade downgrade precision accuracy round_mode div_scale

       Example:

               $new_cfg = Math::BigInt->config( { trap_inf => 1, precision => 5 } );

       accuracy

               $x->accuracy(5);                # local for $x
               CLASS->accuracy(5);             # global for all members of CLASS
               $A = $x->accuracy();            # read out
               $A = CLASS->accuracy();         # read out

       Set or get the global or local accuracy, aka how many sig-
       nificant digits the results have.

       Please see the section about "ACCURACY AND PRECISION" for
       further details.

       Value must be greater than zero. Pass an undef value to
       disable it:




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               $x->accuracy(undef);
               Math::BigInt->accuracy(undef);

       Returns the current accuracy. For "$x-"accuracy()> it will
       return either the local accuracy, or if not defined, the
       global. This means the return value represents the accu-
       racy that will be in effect for $x:

               $y = Math::BigInt->new(1234567);        # unrounded
               print Math::BigInt->accuracy(4),"\n";   # set 4, print 4
               $x = Math::BigInt->new(123456);         # will be automatically rounded
               print "$x $y\n";                        # '123500 1234567'
               print $x->accuracy(),"\n";              # will be 4
               print $y->accuracy(),"\n";              # also 4, since global is 4
               print Math::BigInt->accuracy(5),"\n";   # set to 5, print 5
               print $x->accuracy(),"\n";              # still 4
               print $y->accuracy(),"\n";              # 5, since global is 5

       Note: Works also for subclasses like Math::BigFloat. Each
       class has it's own globals separated from Math::BigInt,
       but it is possible to subclass Math::BigInt and make the
       globals of the subclass aliases to the ones from
       Math::BigInt.

       precision

               $x->precision(-2);              # local for $x, round right of the dot
               $x->precision(2);               # ditto, but round left of the dot
               CLASS->accuracy(5);             # global for all members of CLASS
               CLASS->precision(-5);           # ditto
               $P = CLASS->precision();        # read out
               $P = $x->precision();           # read out

       Set or get the global or local precision, aka how many
       digits the result has after the dot (or where to round it
       when passing a positive number). In Math::BigInt, passing
       a negative number precision has no effect since no numbers
       have digits after the dot.

       Please see the section about "ACCURACY AND PRECISION" for
       further details.

       Value must be greater than zero. Pass an undef value to
       disable it:

               $x->precision(undef);
               Math::BigInt->precision(undef);

       Returns the current precision. For "$x-"precision()> it
       will return either the local precision of $x, or if not
       defined, the global. This means the return value repre-
       sents the accuracy that will be in effect for $x:





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               $y = Math::BigInt->new(1234567);        # unrounded
               print Math::BigInt->precision(4),"\n";  # set 4, print 4
               $x = Math::BigInt->new(123456);         # will be automatically rounded

       Note: Works also for subclasses like Math::BigFloat. Each
       class has it's own globals separated from Math::BigInt,
       but it is possible to subclass Math::BigInt and make the
       globals of the subclass aliases to the ones from
       Math::BigInt.

       brsft

               $x->brsft($y,$n);

       Shifts $x right by $y in base $n. Default is base 2, used
       are usually 10 and 2, but others work, too.

       Right shifting usually amounts to dividing $x by $n ** $y
       and truncating the result:

               $x = Math::BigInt->new(10);
               $x->brsft(1);                   # same as $x >> 1: 5
               $x = Math::BigInt->new(1234);
               $x->brsft(2,10);                # result 12

       There is one exception, and that is base 2 with negative
       $x:

               $x = Math::BigInt->new(-5);
               print $x->brsft(1);

       This will print -3, not -2 (as it would if you divide -5
       by 2 and truncate the result).

       new

               $x = Math::BigInt->new($str,$A,$P,$R);

       Creates a new BigInt object from a scalar or another Big-
       Int object. The input is accepted as decimal, hex (with
       leading '0x') or binary (with leading '0b').

       See Input for more info on accepted input formats.

       bnan

               $x = Math::BigInt->bnan();

       Creates a new BigInt object representing NaN (Not A Num-
       ber).  If used on an object, it will set it to NaN:

               $x->bnan();





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       bzero

               $x = Math::BigInt->bzero();

       Creates a new BigInt object representing zero.  If used on
       an object, it will set it to zero:

               $x->bzero();

       binf

               $x = Math::BigInt->binf($sign);

       Creates a new BigInt object representing infinity. The
       optional argument is either '-' or '+', indicating whether
       you want infinity or minus infinity.  If used on an
       object, it will set it to infinity:

               $x->binf();
               $x->binf('-');

       bone

               $x = Math::BigInt->binf($sign);

       Creates a new BigInt object representing one. The optional
       argument is either '-' or '+', indicating whether you want
       one or minus one.  If used on an object, it will set it to
       one:

               $x->bone();             # +1
               $x->bone('-');          # -1

       is_one()/is_zero()/is_nan()/is_inf()

               $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_inf();                   # true if +inf
               $x->is_inf('-');                # true if -inf (sign is default '+')

       These methods all test the BigInt for beeing one specific
       value and return true or false depending on the input.
       These are faster than doing something like:

               if ($x == 0)

       is_pos()/is_neg()

               $x->is_pos();                   # true if >= 0
               $x->is_neg();                   # true if <  0

       The methods return true if the argument is positive or



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       negative, respectively.  "NaN" is neither positive nor
       negative, while "+inf" counts as positive, and "-inf" is
       negative. A "zero" is positive.

       These methods are only testing the sign, and not the
       value.

       "is_positive()" and "is_negative()" are aliase to
       "is_pos()" and "is_neg()", respectively. "is_positive()"
       and "is_negative()" were introduced in v1.36, while
       "is_pos()" and "is_neg()" were only introduced in v1.68.

       is_odd()/is_even()/is_int()

               $x->is_odd();                   # true if odd, false for even
               $x->is_even();                  # true if even, false for odd
               $x->is_int();                   # true if $x is an integer

       The return true when the argument satisfies the condition.
       "NaN", "+inf", "-inf" are not integers and are neither odd
       nor even.

       In BigInt, all numbers except "NaN", "+inf" and "-inf" are
       integers.

       bcmp

               $x->bcmp($y);

       Compares $x with $y and takes the sign into account.
       Returns -1, 0, 1 or undef.

       bacmp

               $x->bacmp($y);

       Compares $x with $y while ignoring their. Returns -1, 0, 1
       or undef.

       sign

               $x->sign();

       Return the sign, of $x, meaning either "+", "-", "-inf",
       "+inf" or NaN.

       digit

               $x->digit($n);          # return the nth digit, counting from right

       If $n is negative, returns the digit counting from left.






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       bneg

               $x->bneg();

       Negate the number, e.g. change the sign between '+' and
       '-', or between '+inf' and '-inf', respectively. Does
       nothing for NaN or zero.

       babs

               $x->babs();

       Set the number to it's absolute value, e.g. change the
       sign from '-' to '+' and from '-inf' to '+inf', respec-
       tively. Does nothing for NaN or positive numbers.

       bnorm

               $x->bnorm();                    # normalize (no-op)

       bnot

               $x->bnot();

       Two's complement (bit wise not). This is equivalent to

               $x->binc()->bneg();

       but faster.

       binc

               $x->binc();                     # increment x by 1

       bdec

               $x->bdec();                     # decrement x by 1

       badd

               $x->badd($y);                   # addition (add $y to $x)

       bsub

               $x->bsub($y);                   # subtraction (subtract $y from $x)

       bmul

               $x->bmul($y);                   # multiplication (multiply $x by $y)

       bdiv

               $x->bdiv($y);                   # divide, set $x to quotient
                                               # return (quo,rem) or quo if scalar



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       bmod

               $x->bmod($y);                   # modulus (x % y)

       bmodinv

               num->bmodinv($mod);             # modular inverse

       Returns the inverse of $num in the given modulus $mod.
       '"NaN"' is returned unless $num is relatively prime to
       $mod, i.e. unless "bgcd($num, $mod)==1".

       bmodpow

               $num->bmodpow($exp,$mod);       # modular exponentation
                                               # ($num**$exp % $mod)

       Returns the value of $num taken to the power $exp in the
       modulus $mod using binary exponentation.  "bmodpow" is far
       superior to writing

               $num ** $exp % $mod

       because it is much faster - it reduces internal variables
       into the modulus whenever possible, so it operates on
       smaller numbers.

       "bmodpow" also supports negative exponents.

               bmodpow($num, -1, $mod)

       is exactly equivalent to

               bmodinv($num, $mod)

       bpow

               $x->bpow($y);                   # power of arguments (x ** y)

       blsft

               $x->blsft($y);          # left shift
               $x->blsft($y,$n);       # left shift, in base $n (like 10)

       brsft

               $x->brsft($y);          # right shift
               $x->brsft($y,$n);       # right shift, in base $n (like 10)

       band

               $x->band($y);                   # bitwise and





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       bior

               $x->bior($y);                   # bitwise inclusive or

       bxor

               $x->bxor($y);                   # bitwise exclusive or

       bnot

               $x->bnot();                     # bitwise not (two's complement)

       bsqrt

               $x->bsqrt();                    # calculate square-root

       bfac

               $x->bfac();                     # factorial of $x (1*2*3*4*..$x)

       round

               $x->round($A,$P,$round_mode);

       Round $x to accuracy $A or precision $P using the round
       mode $round_mode.

       bround

               $x->bround($N);               # accuracy: preserve $N digits

       bfround

               $x->bfround($N);              # round to $Nth digit, no-op for BigInts

       bfloor

               $x->bfloor();

       Set $x to the integer less or equal than $x. This is a no-
       op in BigInt, but does change $x in BigFloat.

       bceil

               $x->bceil();

       Set $x to the integer greater or equal than $x. This is a
       no-op in BigInt, but does change $x in BigFloat.

       bgcd

               bgcd(@values);          # greatest common divisor (no OO style)





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Math::BigInt(3p) Perl Programmers Reference GuideMath::BigInt(3p)


       blcm

               blcm(@values);          # lowest common multiplicator (no OO style)

       head2 length

               $x->length();
               ($xl,$fl) = $x->length();

       Returns the number of digits in the decimal representation
       of the number.  In list context, returns the length of the
       integer and fraction part. For BigInt's, the length of the
       fraction part will always be 0.

       exponent

               $x->exponent();

       Return the exponent of $x as BigInt.

       mantissa

               $x->mantissa();

       Return the signed mantissa of $x as BigInt.

       parts

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

       copy

               $x->copy();             # make a true copy of $x (unlike $y = $x;)

       as_int

               $x->as_int();

       Returns $x as a BigInt (truncated towards zero). In BigInt
       this is the same as "copy()".

       "as_number()" is an alias to this method. "as_number" was
       introduced in v1.22, while "as_int()" was only introduced
       in v1.68.

       bstr

               $x->bstr();

       Returns a normalized string represantation of $x.







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       bsstr

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

       as_hex

               $x->as_hex();           # as signed hexadecimal string with prefixed 0x

       as_bin

               $x->as_bin();           # as signed binary string with prefixed 0b

ACCURACY and PRECISION
       Since version v1.33, Math::BigInt and Math::BigFloat have
       full support for accuracy and precision based rounding,
       both automatically after every operation, as well as manu-
       ally.

       This section describes the accuracy/precision handling in
       Math::Big* as it used to be and as it is now, complete
       with an explanation of all terms and abbreviations.

       Not yet implemented things (but with correct description)
       are marked with '!', things that need to be answered are
       marked with '?'.

       In the next paragraph follows a short description of terms
       used here (because these may differ from terms used by
       others people or documentation).

       During the rest of this document, the shortcuts A (for
       accuracy), P (for precision), F (fallback) and R (rounding
       mode) will be used.

       Precision P

       A fixed number of digits before (positive) or after (nega-
       tive) the decimal point. For example, 123.45 has a preci-
       sion of -2. 0 means an integer like 123 (or 120). A preci-
       sion of 2 means two digits to the left of the decimal
       point are zero, so 123 with P = 1 becomes 120. Note that
       numbers with zeros before the decimal point may have dif-
       ferent precisions, because 1200 can have p = 0, 1 or 2
       (depending on what the inital value was). It could also
       have p < 0, when the digits after the decimal point are
       zero.

       The string output (of floating point numbers) will be
       padded with zeros:








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               Initial value   P       A       Result          String
               ------------------------------------------------------------
               1234.01         -3              1000            1000
               1234            -2              1200            1200
               1234.5          -1              1230            1230
               1234.001        1               1234            1234.0
               1234.01         0               1234            1234
               1234.01         2               1234.01         1234.01
               1234.01         5               1234.01         1234.01000

       For BigInts, no padding occurs.

       Accuracy A

       Number of significant digits. Leading zeros are not
       counted. A number may have an accuracy greater than the
       non-zero digits when there are zeros in it or trailing
       zeros. For example, 123.456 has A of 6, 10203 has 5,
       123.0506 has 7, 123.450000 has 8 and 0.000123 has 3.

       The string output (of floating point numbers) will be
       padded with zeros:

               Initial value   P       A       Result          String
               ------------------------------------------------------------
               1234.01                 3       1230            1230
               1234.01                 6       1234.01         1234.01
               1234.1                  8       1234.1          1234.1000

       For BigInts, no padding occurs.

       Fallback F

       When both A and P are undefined, this is used as a fall-
       back accuracy when dividing numbers.

       Rounding mode R

       When rounding a number, different 'styles' or 'kinds' of
       rounding are possible. (Note that random rounding, as in
       Math::Round, is not implemented.)

       'trunc'
         truncation invariably removes all digits following the
         rounding place, replacing them with zeros. Thus, 987.65
         rounded to tens (P=1) becomes 980, and rounded to the
         fourth sigdig becomes 987.6 (A=4). 123.456 rounded to
         the second place after the decimal point (P=-2) becomes
         123.46.

         All other implemented styles of rounding attempt to
         round to the "nearest digit." If the digit D immediately
         to the right of the rounding place (skipping the decimal
         point) is greater than 5, the number is incremented at



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         the rounding place (possibly causing a cascade of incre-
         mentation): e.g. when rounding to units, 0.9 rounds to
         1, and -19.9 rounds to -20. If D < 5, the number is sim-
         ilarly truncated at the rounding place: e.g. when round-
         ing to units, 0.4 rounds to 0, and -19.4 rounds to -19.

         However the results of other styles of rounding differ
         if the digit immediately to the right of the rounding
         place (skipping the decimal point) is 5 and if there are
         no digits, or no digits other than 0, after that 5. In
         such cases:

       'even'
         rounds the digit at the rounding place to 0, 2, 4, 6, or
         8 if it is not already. E.g., when rounding to the first
         sigdig, 0.45 becomes 0.4, -0.55 becomes -0.6, but 0.4501
         becomes 0.5.

       'odd'
         rounds the digit at the rounding place to 1, 3, 5, 7, or
         9 if it is not already. E.g., when rounding to the first
         sigdig, 0.45 becomes 0.5, -0.55 becomes -0.5, but 0.5501
         becomes 0.6.

       '+inf'
         round to plus infinity, i.e. always round up. E.g., when
         rounding to the first sigdig, 0.45 becomes 0.5, -0.55
         becomes -0.5, and 0.4501 also becomes 0.5.

       '-inf'
         round to minus infinity, i.e. always round down. E.g.,
         when rounding to the first sigdig, 0.45 becomes 0.4,
         -0.55 becomes -0.6, but 0.4501 becomes 0.5.

       'zero'
         round to zero, i.e. positive numbers down, negative ones
         up.  E.g., when rounding to the first sigdig, 0.45
         becomes 0.4, -0.55 becomes -0.5, but 0.4501 becomes 0.5.

       The handling of A & P in MBI/MBF (the old core code
       shipped with Perl versions <= 5.7.2) is like this:

       Precision
           * ffround($p) is able to round to $p number of digits after the decimal
             point
           * otherwise P is unused

       Accuracy (significant digits)









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           * fround($a) rounds to $a significant digits
           * only fdiv() and fsqrt() take A as (optional) paramater
             + other operations simply create the same number (fneg etc), or more (fmul)
               of digits
             + rounding/truncating is only done when explicitly calling one of fround
               or ffround, and never for BigInt (not implemented)
           * fsqrt() simply hands its accuracy argument over to fdiv.
           * the documentation and the comment in the code indicate two different ways
             on how fdiv() determines the maximum number of digits it should calculate,
             and the actual code does yet another thing
             POD:
               max($Math::BigFloat::div_scale,length(dividend)+length(divisor))
             Comment:
               result has at most max(scale, length(dividend), length(divisor)) digits
             Actual code:
               scale = max(scale, length(dividend)-1,length(divisor)-1);
               scale += length(divisior) - length(dividend);
             So for lx = 3, ly = 9, scale = 10, scale will actually be 16 (10+9-3).
             Actually, the 'difference' added to the scale is calculated from the
             number of "significant digits" in dividend and divisor, which is derived
             by looking at the length of the mantissa. Which is wrong, since it includes
             the + sign (oops) and actually gets 2 for '+100' and 4 for '+101'. Oops
             again. Thus 124/3 with div_scale=1 will get you '41.3' based on the strange
             assumption that 124 has 3 significant digits, while 120/7 will get you
             '17', not '17.1' since 120 is thought to have 2 significant digits.
             The rounding after the division then uses the remainder and $y to determine
             wether it must round up or down.
          ?  I have no idea which is the right way. That's why I used a slightly more
          ?  simple scheme and tweaked the few failing testcases to match it.

       This is how it works now:

       Setting/Accessing
           * You can set the A global via C<< Math::BigInt->accuracy() >> or
             C<< Math::BigFloat->accuracy() >> or whatever class you are using.
           * You can also set P globally by using C<< Math::SomeClass->precision() >>
             likewise.
           * Globals are classwide, and not inherited by subclasses.
           * to undefine A, use C<< Math::SomeCLass->accuracy(undef); >>
           * to undefine P, use C<< Math::SomeClass->precision(undef); >>
           * Setting C<< Math::SomeClass->accuracy() >> clears automatically
             C<< Math::SomeClass->precision() >>, and vice versa.
           * To be valid, A must be > 0, P can have any value.
           * If P is negative, this means round to the P'th place to the right of the
             decimal point; positive values mean to the left of the decimal point.
             P of 0 means round to integer.
           * to find out the current global A, use C<< Math::SomeClass->accuracy() >>
           * to find out the current global P, use C<< Math::SomeClass->precision() >>
           * use C<< $x->accuracy() >> respective C<< $x->precision() >> for the local
             setting of C<< $x >>.
           * Please note that C<< $x->accuracy() >> respecive C<< $x->precision() >>
             return eventually defined global A or P, when C<< $x >>'s A or P is not
             set.




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       Creating numbers
           * When you create a number, you can give it's desired A or P via:
             $x = Math::BigInt->new($number,$A,$P);
           * Only one of A or P can be defined, otherwise the result is NaN
           * If no A or P is give ($x = Math::BigInt->new($number) form), then the
             globals (if set) will be used. Thus changing the global defaults later on
             will not change the A or P of previously created numbers (i.e., A and P of
             $x will be what was in effect when $x was created)
           * If given undef for A and P, B<no> rounding will occur, and the globals will
             B<not> be used. This is used by subclasses to create numbers without
             suffering rounding in the parent. Thus a subclass is able to have it's own
             globals enforced upon creation of a number by using
             C<< $x = Math::BigInt->new($number,undef,undef) >>:

                 use Math::BigInt::SomeSubclass;
                 use Math::BigInt;

                 Math::BigInt->accuracy(2);
                 Math::BigInt::SomeSubClass->accuracy(3);
                 $x = Math::BigInt::SomeSubClass->new(1234);

             $x is now 1230, and not 1200. A subclass might choose to implement
             this otherwise, e.g. falling back to the parent's A and P.

       Usage
           * If A or P are enabled/defined, they are used to round the result of each
             operation according to the rules below
           * Negative P is ignored in Math::BigInt, since BigInts never have digits
             after the decimal point
           * Math::BigFloat uses Math::BigInt internally, but setting A or P inside
             Math::BigInt as globals does not tamper with the parts of a BigFloat.
             A flag is used to mark all Math::BigFloat numbers as 'never round'.

       Precedence























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           * It only makes sense that a number has only one of A or P at a time.
             If you set either A or P on one object, or globally, the other one will
             be automatically cleared.
           * If two objects are involved in an operation, and one of them has A in
             effect, and the other P, this results in an error (NaN).
           * A takes precendence over P (Hint: A comes before P).
             If neither of them is defined, nothing is used, i.e. the result will have
             as many digits as it can (with an exception for fdiv/fsqrt) and will not
             be rounded.
           * There is another setting for fdiv() (and thus for fsqrt()). If neither of
             A or P is defined, fdiv() will use a fallback (F) of $div_scale digits.
             If either the dividend's or the divisor's mantissa has more digits than
             the value of F, the higher value will be used instead of F.
             This is to limit the digits (A) of the result (just consider what would
             happen with unlimited A and P in the case of 1/3 :-)
           * fdiv will calculate (at least) 4 more digits than required (determined by
             A, P or F), and, if F is not used, round the result
             (this will still fail in the case of a result like 0.12345000000001 with A
             or P of 5, but this can not be helped - or can it?)
           * Thus you can have the math done by on Math::Big* class in two modi:
             + never round (this is the default):
               This is done by setting A and P to undef. No math operation
               will round the result, with fdiv() and fsqrt() as exceptions to guard
               against overflows. You must explicitely call bround(), bfround() or
               round() (the latter with parameters).
               Note: Once you have rounded a number, the settings will 'stick' on it
               and 'infect' all other numbers engaged in math operations with it, since
               local settings have the highest precedence. So, to get SaferRound[tm],
               use a copy() before rounding like this:

                 $x = Math::BigFloat->new(12.34);
                 $y = Math::BigFloat->new(98.76);
                 $z = $x * $y;                           # 1218.6984
                 print $x->copy()->fround(3);            # 12.3 (but A is now 3!)
                 $z = $x * $y;                           # still 1218.6984, without
                                                         # copy would have been 1210!

             + round after each op:
               After each single operation (except for testing like is_zero()), the
               method round() is called and the result is rounded appropriately. By
               setting proper values for A and P, you can have all-the-same-A or
               all-the-same-P modes. For example, Math::Currency might set A to undef,
               and P to -2, globally.

          ?Maybe an extra option that forbids local A & P settings would be in order,
          ?so that intermediate rounding does not 'poison' further math?

       Overriding globals









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           * you will be able to give A, P and R as an argument to all the calculation
             routines; the second parameter is A, the third one is P, and the fourth is
             R (shift right by one for binary operations like badd). P is used only if
             the first parameter (A) is undefined. These three parameters override the
             globals in the order detailed as follows, i.e. the first defined value
             wins:
             (local: per object, global: global default, parameter: argument to sub)
               + parameter A
               + parameter P
               + local A (if defined on both of the operands: smaller one is taken)
               + local P (if defined on both of the operands: bigger one is taken)
               + global A
               + global P
               + global F
           * fsqrt() will hand its arguments to fdiv(), as it used to, only now for two
             arguments (A and P) instead of one

       Local settings
           * You can set A or P locally by using C<< $x->accuracy() >> or
             C<< $x->precision() >>
             and thus force different A and P for different objects/numbers.
           * Setting A or P this way immediately rounds $x to the new value.
           * C<< $x->accuracy() >> clears C<< $x->precision() >>, and vice versa.

       Rounding
           * the rounding routines will use the respective global or local settings.
             fround()/bround() is for accuracy rounding, while ffround()/bfround()
             is for precision
           * the two rounding functions take as the second parameter one of the
             following rounding modes (R):
             'even', 'odd', '+inf', '-inf', 'zero', 'trunc'
           * you can set/get the global R by using C<< Math::SomeClass->round_mode() >>
             or by setting C<< $Math::SomeClass::round_mode >>
           * after each operation, C<< $result->round() >> is called, and the result may
             eventually be rounded (that is, if A or P were set either locally,
             globally or as parameter to the operation)
           * to manually round a number, call C<< $x->round($A,$P,$round_mode); >>
             this will round the number by using the appropriate rounding function
             and then normalize it.
           * rounding modifies the local settings of the number:

                 $x = Math::BigFloat->new(123.456);
                 $x->accuracy(5);
                 $x->bround(4);

             Here 4 takes precedence over 5, so 123.5 is the result and $x->accuracy()
             will be 4 from now on.

       Default values
           * R: 'even'
           * F: 40
           * A: undef
           * P: undef




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       Remarks
           * The defaults are set up so that the new code gives the same results as
             the old code (except in a few cases on fdiv):
             + Both A and P are undefined and thus will not be used for rounding
               after each operation.
             + round() is thus a no-op, unless given extra parameters A and P

INTERNALS
       The actual numbers are stored as unsigned big integers
       (with seperate sign).  You should neither care about nor
       depend on the internal representation; it might change
       without notice. Use only method calls like "$x->sign();"
       instead relying on the internal hash keys like in
       "$x->{sign};".

       MATH LIBRARY

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

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

       You can change this by using:

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

       Since Math::BigInt::GMP is in almost all cases faster than
       Calc (especially in cases involving really big numbers,
       where it is much faster), and there is no penalty if
       Math::BigInt::GMP is not installed, it is a good idea to
       always use the following:

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

       Different low-level libraries use different formats to
       store the numbers. You should not depend on the number
       having a specific format.

       See the respective math library 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'



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       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.

       mantissa(), exponent() and parts()

       "mantissa()" and "exponent()" return the said parts of the
       BigInt 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 that gives you
       both of them in one go. Both the returned mantissa and
       exponent have a sign.

       Currently, for BigInts $e is always 0, except for NaN,
       +inf and -inf, where it is "NaN"; and for "$x == 0", where
       it is 1 (to be compatible with Math::BigFloat's internal
       representation of a zero as 0E1).

       $m is currently just a copy of the original number. The
       relation between $e and $m will stay always the same,
       though their real values might change.

EXAMPLES
         use Math::BigInt;

         sub bint { Math::BigInt->new(shift); }

         $x = Math::BigInt->bstr("1234")       # string "1234"
         $x = "$x";                            # same as bstr()
         $x = Math::BigInt->bneg("1234");      # BigInt "-1234"
         $x = Math::BigInt->babs("-12345");    # BigInt "12345"
         $x = Math::BigInt->bnorm("-0 00");    # BigInt "0"
         $x = bint(1) + bint(2);               # BigInt "3"
         $x = bint(1) + "2";                   # ditto (auto-BigIntify of "2")
         $x = bint(1);                         # BigInt "1"
         $x = $x + 5 / 2;                      # BigInt "3"
         $x = $x ** 3;                         # BigInt "27"
         $x *= 2;                              # BigInt "54"
         $x = Math::BigInt->new(0);            # BigInt "0"
         $x--;                                 # BigInt "-1"
         $x = Math::BigInt->badd(4,5)          # BigInt "9"
         print $x->bsstr();                    # 9e+0

       Examples for rounding:

         use Math::BigFloat;
         use Test;





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         $x = Math::BigFloat->new(123.4567);
         $y = Math::BigFloat->new(123.456789);
         Math::BigFloat->accuracy(4);          # no more A than 4

         ok ($x->copy()->fround(),123.4);      # even rounding
         print $x->copy()->fround(),"\n";      # 123.4
         Math::BigFloat->round_mode('odd');    # round to odd
         print $x->copy()->fround(),"\n";      # 123.5
         Math::BigFloat->accuracy(5);          # no more A than 5
         Math::BigFloat->round_mode('odd');    # round to odd
         print $x->copy()->fround(),"\n";      # 123.46
         $y = $x->copy()->fround(4),"\n";      # A = 4: 123.4
         print "$y, ",$y->accuracy(),"\n";     # 123.4, 4

         Math::BigFloat->accuracy(undef);      # A not important now
         Math::BigFloat->precision(2);         # P important
         print $x->copy()->bnorm(),"\n";       # 123.46
         print $x->copy()->fround(),"\n";      # 123.46

       Examples for converting:

         my $x = Math::BigInt->new('0b1'.'01' x 123);
         print "bin: ",$x->as_bin()," hex:",$x->as_hex()," dec: ",$x,"\n";

Autocreating constants
       After "use Math::BigInt ':constant'" all the integer deci-
       mal, hexadecimal and binary constants in the given scope
       are converted to "Math::BigInt".  This conversion happens
       at compile time.

       In particular,

         perl -MMath::BigInt=:constant -e 'print 2**100,"\n"'

       prints the integer value of "2**100". Note that without
       conversion of constants the expression 2**100 will be cal-
       culated as perl scalar.

       Please note that strings and floating point constants are
       not affected, so that

               use Math::BigInt qw/:constant/;

               $x = 1234567890123456789012345678901234567890
                       + 123456789123456789;
               $y = '1234567890123456789012345678901234567890'
                       + '123456789123456789';

       do not work. You need an explicit Math::BigInt->new()
       around one of the operands. You should also quote large
       constants to protect loss of precision:

               use Math::BigInt;




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               $x = Math::BigInt->new('1234567889123456789123456789123456789');

       Without the quotes Perl would convert the large number to
       a floating point constant at compile time and then hand
       the result to BigInt, which results in an truncated result
       or a NaN.

       This also applies to integers that look like floating
       point constants:

               use Math::BigInt ':constant';

               print ref(123e2),"\n";
               print ref(123.2e2),"\n";

       will print nothing but newlines. Use either bignum or
       Math::BigFloat to get this to work.

PERFORMANCE
       Using the form $x += $y; etc over $x = $x + $y is faster,
       since a copy of $x must be made in the second case. For
       long numbers, the copy can eat up to 20% of the work (in
       the case of addition/subtraction, less for multiplica-
       tion/division). If $y is very small compared to $x, the
       form $x += $y is MUCH faster than $x = $x + $y since mak-
       ing the copy of $x takes more time then the actual addi-
       tion.

       With a technique called copy-on-write, the cost of copying
       with overload could be minimized or even completely
       avoided. A test implementation of COW did show performance
       gains for overloaded math, but introduced a performance
       loss due to a constant overhead for all other operatons.
       So Math::BigInt does currently not COW.

       The rewritten version of this module (vs. v0.01) is slower
       on certain operations, like "new()", "bstr()" and
       "numify()". The reason are that it does now more work and
       handles much more cases. The time spent in these opera-
       tions is usually gained in the other math operations so
       that code on the average should get (much) faster. If they
       don't, please contact the author.

       Some operations may be slower for small numbers, but are
       significantly faster for big numbers. Other operations are
       now constant (O(1), like "bneg()", "babs()" etc), instead
       of O(N) and thus nearly always take much less time.  These
       optimizations were done on purpose.

       If you find the Calc module to slow, try to install any of
       the replacement modules and see if they help you.






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       Alternative math libraries

       You can use an alternative library to drive Math::BigInt
       via:

               use Math::BigInt lib => 'Module';

       See "MATH LIBRARY" for more information.

       For more benchmark results see <http://blood-
       gate.com/perl/benchmarks.html>.

       SUBCLASSING


Subclassing Math::BigInt
       The basic design of Math::BigInt allows simple subclasses
       with very little work, as long as a few simple rules are
       followed:

       o The public API must remain consistent, i.e. if a sub-
         class is overloading addition, the sub-class must use
         the same name, in this case badd(). The reason for this
         is that Math::BigInt is optimized to call the object
         methods directly.

       o The private object hash keys like "$x-"{sign}> may not
         be changed, but additional keys can be added, like
         "$x-"{_custom}>.

       o Accessor functions are available for all existing object
         hash keys and should be used instead of directly access-
         ing the internal hash keys. The reason for this is that
         Math::BigInt itself has a pluggable interface which per-
         mits it to support different storage methods.

       More complex sub-classes may have to replicate more of the
       logic internal of Math::BigInt if they need to change more
       basic behaviors. A subclass that needs to merely change
       the output only needs to overload "bstr()".

       All other object methods and overloaded functions can be
       directly inherited from the parent class.

       At the very minimum, any subclass will need to provide
       it's own "new()" and can store additional hash keys in the
       object. There are also some package globals that must be
       defined, e.g.:

         # Globals
         $accuracy = undef;
         $precision = -2;       # round to 2 decimal places
         $round_mode = 'even';
         $div_scale = 40;



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       Additionally, you might want to provide the following two
       globals to allow auto-upgrading and auto-downgrading to
       work correctly:

         $upgrade = undef;
         $downgrade = undef;

       This allows Math::BigInt to correctly retrieve package
       globals from the subclass, like $SubClass::precision.  See
       t/Math/BigInt/Subclass.pm or t/Math/BigFloat/SubClass.pm
       completely functional subclass examples.

       Don't forget to

               use overload;

       in your subclass to automatically inherit the overloading
       from the parent. If you like, you can change part of the
       overloading, look at Math::String for an example.

UPGRADING
       When used like this:

               use Math::BigInt upgrade => 'Foo::Bar';

       certain operations will 'upgrade' their calculation and
       thus the result to the class Foo::Bar. Usually this is
       used in conjunction with Math::BigFloat:

               use Math::BigInt upgrade => 'Math::BigFloat';

       As a shortcut, you can use the module "bignum":

               use bignum;

       Also good for oneliners:

               perl -Mbignum -le 'print 2 ** 255'

       This makes it possible to mix arguments of different
       classes (as in 2.5 + 2) as well es preserve accuracy (as
       in sqrt(3)).

       Beware: This feature is not fully implemented yet.

       Auto-upgrade

       The following methods upgrade themselves unconditionally;
       that is if upgrade is in effect, they will always hand up
       their work:

       bsqrt()
       div()




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       blog()

       Beware: This list is not complete.

       All other methods upgrade themselves only when one (or
       all) of their arguments are of the class mentioned in
       $upgrade (This might change in later versions to a more
       sophisticated scheme):

BUGS
       broot() does not work
         The broot() function in BigInt may only work for small
         values. This will be fixed in a later version.

       Out of Memory!
         Under Perl prior to 5.6.0 having an "use Math::BigInt
         ':constant';" and "eval()" in your code will crash with
         "Out of memory". This is probably an overload/exporter
         bug. You can workaround by not having "eval()" and
         ':constant' at the same time or upgrade your Perl to a
         newer version.

       Fails to load Calc on Perl prior 5.6.0
         Since eval(' use ...') can not be used in conjunction
         with ':constant', BigInt will fall back to eval {
         require ... } when loading the math lib on Perls prior
         to 5.6.0. This simple replaces '::' with '/' and thus
         might fail on filesystems using a different seperator.

CAVEATS
       Some things might not work as you expect them. Below is
       documented what is known to be troublesome:

       bstr(), bsstr() and 'cmp'
        Both "bstr()" and "bsstr()" as well as automated
        stringify via overload now drop the leading '+'. The old
        code would return '+3', the new returns '3'.  This is to
        be consistent with Perl and to make "cmp" (especially
        with overloading) to work as you expect. It also solves
        problems with "Test.pm", because it's "ok()" uses 'eq'
        internally.

        Mark Biggar said, when asked about to drop the '+' alto-
        gether, or make only "cmp" work:

                I agree (with the first alternative), don't add the '+' on positive
                numbers.  It's not as important anymore with the new internal
                form for numbers.  It made doing things like abs and neg easier,
                but those have to be done differently now anyway.

        So, the following examples will now work all as expected:






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                use Test;
                BEGIN { plan tests => 1 }
                use Math::BigInt;

                my $x = new Math::BigInt 3*3;
                my $y = new Math::BigInt 3*3;

                ok ($x,3*3);
                print "$x eq 9" if $x eq $y;
                print "$x eq 9" if $x eq '9';
                print "$x eq 9" if $x eq 3*3;

        Additionally, the following still works:

                print "$x == 9" if $x == $y;
                print "$x == 9" if $x == 9;
                print "$x == 9" if $x == 3*3;

        There is now a "bsstr()" method to get the string in sci-
        entific notation aka 1e+2 instead of 100. Be advised that
        overloaded 'eq' always uses bstr() for comparisation, but
        Perl will represent some numbers as 100 and others as
        1e+308. If in doubt, convert both arguments to Math::Big-
        Int before comparing them as strings:

                use Test;
                BEGIN { plan tests => 3 }
                use Math::BigInt;

                $x = Math::BigInt->new('1e56'); $y = 1e56;
                ok ($x,$y);                     # will fail
                ok ($x->bsstr(),$y);            # okay
                $y = Math::BigInt->new($y);
                ok ($x,$y);                     # okay

        Alternatively, simple use "<=>" for comparisations, this
        will get it always right. There is not yet a way to get a
        number automatically represented as a string that matches
        exactly the way Perl represents it.

       int()
        "int()" will return (at least for Perl v5.7.1 and up)
        another BigInt, not a Perl scalar:

                $x = Math::BigInt->new(123);
                $y = int($x);                           # BigInt 123
                $x = Math::BigFloat->new(123.45);
                $y = int($x);                           # BigInt 123

        In all Perl versions you can use "as_number()" for the
        same effect:

                $x = Math::BigFloat->new(123.45);
                $y = $x->as_number();                   # BigInt 123



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        This also works for other subclasses, like Math::String.

        It is yet unlcear whether overloaded int() should return
        a scalar or a BigInt.

       length
        The following will probably not do what you expect:

                $c = Math::BigInt->new(123);
                print $c->length(),"\n";                # prints 30

        It prints both the number of digits in the number and in
        the fraction part since print calls "length()" in list
        context. Use something like:

                print scalar $c->length(),"\n";         # prints 3

       bdiv
        The following will probably not do what you expect:

                print $c->bdiv(10000),"\n";

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

                print $c / 10000,"\n";
                print scalar $c->bdiv(10000),"\n";  # or if you want to modify $c

        instead.

        The quotient is always the greatest integer less than or
        equal to the real-valued quotient of the two operands,
        and the remainder (when it is nonzero) always has the
        same sign as the second operand; so, for example,

                  1 / 4  => ( 0, 1)
                  1 / -4 => (-1,-3)
                 -3 / 4  => (-1, 1)
                 -3 / -4 => ( 0,-3)
                -11 / 2  => (-5,1)
                 11 /-2  => (-5,-1)

        As a consequence, the behavior of the operator % agrees
        with the behavior of Perl's built-in % operator (as docu-
        mented in the perlop manpage), and the equation

                $x == ($x / $y) * $y + ($x % $y)

        holds true for any $x and $y, which justifies calling the
        two return values of bdiv() the quotient and remainder.
        The only exception to this rule are when $y == 0 and $x
        is negative, then the remainder will also be negative.
        See below under "infinity handling" for the reasoning



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        behing this.

        Perl's 'use integer;' changes the behaviour of % and /
        for scalars, but will not change BigInt's way to do
        things. This is because under 'use integer' Perl will do
        what the underlying C thinks is right and this is differ-
        ent for each system. If you need BigInt's behaving
        exactly like Perl's 'use integer', bug the author to
        implement it ;)

       infinity handling
        Here are some examples that explain the reasons why cer-
        tain results occur while handling infinity:

        The following table shows the result of the division and
        the remainder, so that the equation above holds true.
        Some "ordinary" cases are strewn in to show more clearly
        the reasoning:

                A /  B  =   C,     R so that C *    B +    R =    A
             =========================================================
                5 /   8 =   0,     5         0 *    8 +    5 =    5
                0 /   8 =   0,     0         0 *    8 +    0 =    0
                0 / inf =   0,     0         0 *  inf +    0 =    0
                0 /-inf =   0,     0         0 * -inf +    0 =    0
                5 / inf =   0,     5         0 *  inf +    5 =    5
                5 /-inf =   0,     5         0 * -inf +    5 =    5
                -5/ inf =   0,    -5         0 *  inf +   -5 =   -5
                -5/-inf =   0,    -5         0 * -inf +   -5 =   -5
               inf/   5 =  inf,    0       inf *    5 +    0 =  inf
              -inf/   5 = -inf,    0      -inf *    5 +    0 = -inf
               inf/  -5 = -inf,    0      -inf *   -5 +    0 =  inf
              -inf/  -5 =  inf,    0       inf *   -5 +    0 = -inf
                 5/   5 =    1,    0         1 *    5 +    0 =    5
                -5/  -5 =    1,    0         1 *   -5 +    0 =   -5
               inf/ inf =    1,    0         1 *  inf +    0 =  inf
              -inf/-inf =    1,    0         1 * -inf +    0 = -inf
               inf/-inf =   -1,    0        -1 * -inf +    0 =  inf
              -inf/ inf =   -1,    0         1 * -inf +    0 = -inf
                 8/   0 =  inf,    8       inf *    0 +    8 =    8
               inf/   0 =  inf,  inf       inf *    0 +  inf =  inf
                 0/   0 =  NaN

        These cases below violate the "remainder has the sign of
        the second of the two arguments", since they wouldn't
        match up otherwise.

                A /  B  =   C,     R so that C *    B +    R =    A
             ========================================================
              -inf/   0 = -inf, -inf      -inf *    0 +  inf = -inf
                -8/   0 = -inf,   -8      -inf *    0 +    8 = -8

       Modifying and =
        Beware of:



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                $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 (except overloaded operators) will modify $y, and vice
        versa.  Or in other words, "=" is only safe if you modify
        your BigInts only via overloaded math. As soon as you use
        a method call it breaks:

                $x->bmul(2);
                print "$x, $y\n";       # prints '10, 10'

        If you want a true copy of $x, use:

                $y = $x->copy();

        You can also chain the calls like this, this will make
        first a copy and then multiply it by 2:

                $y = $x->copy()->bmul(2);

        See also the documentation for overload.pm regarding "=".

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

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

        The form "$x **= $y" is faster than "$x = $x ** $y;",
        though.

       Overloading -$x
        The following:

                $x = -$x;

        is slower than

                $x->bneg();

        since overload calls "sub($x,0,1);" instead of "neg($x)".
        The first variant needs to preserve $x since it does not
        know that it later will get overwritten.  This makes a
        copy of $x and takes O(N), but $x->bneg() is O(1).




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        With Copy-On-Write, this issue would be gone, but C-o-W
        is not implemented since it is slower for all other
        things.

       Mixing different object types
        In Perl you will get a floating point value if you do one
        of the following:

                $float = 5.0 + 2;
                $float = 2 + 5.0;
                $float = 5 / 2;

        With overloaded math, only the first two variants will
        result in a BigFloat:

                use Math::BigInt;
                use Math::BigFloat;

                $mbf = Math::BigFloat->new(5);
                $mbi2 = Math::BigInteger->new(5);
                $mbi = Math::BigInteger->new(2);

                                                # what actually gets called:
                $float = $mbf + $mbi;           # $mbf->badd()
                $float = $mbf / $mbi;           # $mbf->bdiv()
                $integer = $mbi + $mbf;         # $mbi->badd()
                $integer = $mbi2 / $mbi;        # $mbi2->bdiv()
                $integer = $mbi2 / $mbf;        # $mbi2->bdiv()

        This is because math with overloaded operators follows
        the first (dominating) operand, and the operation of that
        is called and returns thus the result. So, Math::Big-
        Int::bdiv() will always return a Math::BigInt, regardless
        whether the result should be a Math::BigFloat or the sec-
        ond operant is one.

        To get a Math::BigFloat you either need to call the oper-
        ation manually, make sure the operands are already of the
        proper type or casted to that type via
        Math::BigFloat->new():

                $float = Math::BigFloat->new($mbi2) / $mbi;     # = 2.5

        Beware of simple "casting" the entire expression, this
        would only convert the already computed result:

                $float = Math::BigFloat->new($mbi2 / $mbi);     # = 2.0 thus wrong!

        Beware also of the order of more complicated expressions
        like:

                $integer = ($mbi2 + $mbi) / $mbf;               # int / float => int
                $integer = $mbi2 / Math::BigFloat->new($mbi);   # ditto




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        If in doubt, break the expression into simpler terms, or
        cast all operands to the desired resulting type.

        Scalar values are a bit different, since:

                $float = 2 + $mbf;
                $float = $mbf + 2;

        will both result in the proper type due to the way the
        overloaded math works.

        This section also applies to other overloaded math pack-
        ages, like Math::String.

        One solution to you problem might be autoupgrad-
        ing|upgrading. See the pragmas bignum, bigint and bigrat
        for an easy way to do this.

       bsqrt()
        "bsqrt()" works only good if the result is a big integer,
        e.g. the square root of 144 is 12, but from 12 the square
        root is 3, regardless of rounding mode. The reason is
        that the result is always truncated to an integer.

        If you want a better approximation of the square root,
        then use:

                $x = Math::BigFloat->new(12);
                Math::BigFloat->precision(0);
                Math::BigFloat->round_mode('even');
                print $x->copy->bsqrt(),"\n";           # 4

                Math::BigFloat->precision(2);
                print $x->bsqrt(),"\n";                 # 3.46
                print $x->bsqrt(3),"\n";                # 3.464

       brsft()
        For negative numbers in base see also brsft.

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

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

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

       The package at <http://search.cpan.org/search?mode=mod-
       ule&query=Math%3A%3ABigInt> contains more documentation



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       including a full version history, testcases, empty sub-
       class files and benchmarks.

AUTHORS
       Original code by Mark Biggar, overloaded interface by Ilya
       Zakharevich.  Completely rewritten by Tels http://blood-
       gate.com in late 2000, 2001 - 2003 and still at it in
       2004.

       Many people contributed in one or more ways to the final
       beast, see the file CREDITS for an (uncomplete) list. If
       you miss your name, please drop me a mail. Thank you!













































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