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.\" ========================================================================
.\"
.IX Title "Math::BigInt 3"
.TH Math::BigInt 3 "2019-10-24" "perl v5.30.2" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Math::BigInt \- Arbitrary size integer/float math package
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& use Math::BigInt;
\&
\& # or make it faster with huge numbers: install (optional)
\& # Math::BigInt::GMP and always use (it falls back to
\& # pure Perl if the GMP library is not installed):
\& # (See also the L<MATH LIBRARY> section!)
\&
\& # warns if Math::BigInt::GMP cannot be found
\& use Math::BigInt lib => \*(AqGMP\*(Aq;
\&
\& # to suppress the warning use this:
\& # use Math::BigInt try => \*(AqGMP\*(Aq;
\&
\& # dies if GMP cannot be loaded:
\& # use Math::BigInt only => \*(AqGMP\*(Aq;
\&
\& my $str = \*(Aq1234567890\*(Aq;
\& my @values = (64, 74, 18);
\& my $n = 1; my $sign = \*(Aq\-\*(Aq;
\&
\& # Configuration methods (may be used as class methods and instance methods)
\&
\& Math::BigInt\->accuracy(); # get class accuracy
\& Math::BigInt\->accuracy($n); # set class accuracy
\& Math::BigInt\->precision(); # get class precision
\& Math::BigInt\->precision($n); # set class precision
\& Math::BigInt\->round_mode(); # get class rounding mode
\& Math::BigInt\->round_mode($m); # set global round mode, must be one of
\& # \*(Aqeven\*(Aq, \*(Aqodd\*(Aq, \*(Aq+inf\*(Aq, \*(Aq\-inf\*(Aq, \*(Aqzero\*(Aq,
\& # \*(Aqtrunc\*(Aq, or \*(Aqcommon\*(Aq
\& Math::BigInt\->config(); # return hash with configuration
\&
\& # Constructor methods (when the class methods below are used as instance
\& # methods, the value is assigned the invocand)
\&
\& $x = Math::BigInt\->new($str); # defaults to 0
\& $x = Math::BigInt\->new(\*(Aq0x123\*(Aq); # from hexadecimal
\& $x = Math::BigInt\->new(\*(Aq0b101\*(Aq); # from binary
\& $x = Math::BigInt\->from_hex(\*(Aqcafe\*(Aq); # from hexadecimal
\& $x = Math::BigInt\->from_oct(\*(Aq377\*(Aq); # from octal
\& $x = Math::BigInt\->from_bin(\*(Aq1101\*(Aq); # from binary
\& $x = Math::BigInt\->from_base(\*(Aqwhy\*(Aq, 36); # from any base
\& $x = Math::BigInt\->bzero(); # create a +0
\& $x = Math::BigInt\->bone(); # create a +1
\& $x = Math::BigInt\->bone(\*(Aq\-\*(Aq); # create a \-1
\& $x = Math::BigInt\->binf(); # create a +inf
\& $x = Math::BigInt\->binf(\*(Aq\-\*(Aq); # create a \-inf
\& $x = Math::BigInt\->bnan(); # create a Not\-A\-Number
\& $x = Math::BigInt\->bpi(); # returns pi
\&
\& $y = $x\->copy(); # make a copy (unlike $y = $x)
\& $y = $x\->as_int(); # return as a Math::BigInt
\&
\& # Boolean methods (these don\*(Aqt 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\*(Aqs number)
\& $x\->blog($base); # logarithm of $x to base $base (e.g., base 2)
\& $x\->bexp(); # calculate e ** $x where e is Euler\*(Aqs 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\*(Aqth 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\*(Aqs 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 a Math::BigInt
\& $x\->exponent(); # return exponent as a Math::BigInt
\& $x\->parts(); # return (mantissa,exponent) as a Math::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\->to_hex(); # as signed hexadecimal string
\& $x\->to_bin(); # as signed binary string
\& $x\->to_oct(); # as signed octal string
\& $x\->to_bytes(); # as byte string
\& $x\->to_base($b); # as string in any base
\&
\& $x\->as_hex(); # as signed hexadecimal string with prefixed 0x
\& $x\->as_bin(); # as signed binary string with prefixed 0b
\& $x\->as_oct(); # as signed octal string with prefixed 0
\&
\& # Other conversion methods
\&
\& $x\->numify(); # return as scalar (might overflow or underflow)
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Math::BigInt provides support for arbitrary precision integers. Overloading is
also provided for Perl operators.
.SS "Input"
.IX Subsection "Input"
Input values to these routines may be any scalar number or string that looks
like a number and represents an integer.
.IP "\(bu" 4
Leading and trailing whitespace is ignored.
.IP "\(bu" 4
Leading and trailing zeros are ignored.
.IP "\(bu" 4
If the string has a \*(L"0x\*(R" prefix, it is interpreted as a hexadecimal number.
.IP "\(bu" 4
If the string has a \*(L"0b\*(R" prefix, it is interpreted as a binary number.
.IP "\(bu" 4
One underline is allowed between any two digits.
.IP "\(bu" 4
If the string can not be interpreted, NaN is returned.
.PP
Octal numbers are typically prefixed by \*(L"0\*(R", but since leading zeros are
stripped, these methods can not automatically recognize octal numbers, so use
the constructor \fBfrom_oct()\fR to interpret octal strings.
.PP
Some examples of valid string input
.PP
.Vb 8
\& Input string Resulting value
\& 123 123
\& 1.23e2 123
\& 12300e\-2 123
\& 0xcafe 51966
\& 0b1101 13
\& 67_538_754 67538754
\& \-4_5_6.7_8_9e+0_1_0 \-4567890000000
.Ve
.PP
Input given as scalar numbers might lose precision. Quote your input to ensure
that no digits are lost:
.PP
.Vb 2
\& $x = Math::BigInt\->new( 56789012345678901234 ); # bad
\& $x = Math::BigInt\->new(\*(Aq56789012345678901234\*(Aq); # good
.Ve
.PP
Currently, Math::BigInt\->\fBnew()\fR 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:
.PP
.Vb 2
\& $zero = Math::BigInt\->bzero();
\& $nan = Math::BigInt\->bnan();
.Ve
.SS "Output"
.IX Subsection "Output"
Output values are usually Math::BigInt objects.
.PP
Boolean operators \f(CW\*(C`is_zero()\*(C'\fR, \f(CW\*(C`is_one()\*(C'\fR, \f(CW\*(C`is_inf()\*(C'\fR, etc. return true or
false.
.PP
Comparison operators \f(CW\*(C`bcmp()\*(C'\fR and \f(CW\*(C`bacmp()\*(C'\fR) return \-1, 0, 1, or
undef.
.SH "METHODS"
.IX Header "METHODS"
.SS "Configuration methods"
.IX Subsection "Configuration methods"
Each of the methods below (except \fBconfig()\fR, \fBaccuracy()\fR and \fBprecision()\fR) accepts
three additional parameters. These arguments \f(CW$A\fR, \f(CW$P\fR and \f(CW$R\fR are
\&\f(CW\*(C`accuracy\*(C'\fR, \f(CW\*(C`precision\*(C'\fR and \f(CW\*(C`round_mode\*(C'\fR. Please see the section about
\&\*(L"\s-1ACCURACY\s0 and \s-1PRECISION\*(R"\s0 for more information.
.PP
Setting a class variable effects all object instance that are created
afterwards.
.IP "\fBaccuracy()\fR" 4
.IX Item "accuracy()"
.Vb 2
\& Math::BigInt\->accuracy(5); # set class accuracy
\& $x\->accuracy(5); # set instance accuracy
\&
\& $A = Math::BigInt\->accuracy(); # get class accuracy
\& $A = $x\->accuracy(); # get instance accuracy
.Ve
.Sp
Set or get the accuracy, i.e., the number of significant digits. The accuracy
must be an integer. If the accuracy is set to \f(CW\*(C`undef\*(C'\fR, no rounding is done.
.Sp
Alternatively, one can round the results explicitly using one of \*(L"\fBround()\fR\*(R",
\&\*(L"\fBbround()\fR\*(R" or \*(L"\fBbfround()\fR\*(R" or by passing the desired accuracy to the method
as an additional parameter:
.Sp
.Vb 4
\& my $x = Math::BigInt\->new(30000);
\& my $y = Math::BigInt\->new(7);
\& print scalar $x\->copy()\->bdiv($y, 2); # prints 4300
\& print scalar $x\->copy()\->bdiv($y)\->bround(2); # prints 4300
.Ve
.Sp
Please see the section about \*(L"\s-1ACCURACY\s0 and \s-1PRECISION\*(R"\s0 for further details.
.Sp
.Vb 4
\& $y = Math::BigInt\->new(1234567); # $y is not rounded
\& Math::BigInt\->accuracy(4); # set class accuracy to 4
\& $x = Math::BigInt\->new(1234567); # $x is rounded automatically
\& print "$x $y"; # prints "1235000 1234567"
\&
\& print $x\->accuracy(); # prints "4"
\& print $y\->accuracy(); # also prints "4", since
\& # class accuracy is 4
\&
\& Math::BigInt\->accuracy(5); # set class accuracy to 5
\& print $x\->accuracy(); # prints "4", since instance
\& # accuracy is 4
\& print $y\->accuracy(); # prints "5", since no instance
\& # accuracy, and class accuracy is 5
.Ve
.Sp
Note: 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.
.IP "\fBprecision()\fR" 4
.IX Item "precision()"
.Vb 2
\& Math::BigInt\->precision(\-2); # set class precision
\& $x\->precision(\-2); # set instance precision
\&
\& $P = Math::BigInt\->precision(); # get class precision
\& $P = $x\->precision(); # get instance precision
.Ve
.Sp
Set or get the precision, i.e., the place to round relative to the decimal
point. The precision must be a integer. Setting the precision to \f(CW$P\fR means that
each number is rounded up or down, depending on the rounding mode, to the
nearest multiple of 10**$P. If the precision is set to \f(CW\*(C`undef\*(C'\fR, no rounding is
done.
.Sp
You might want to use \*(L"\fBaccuracy()\fR\*(R" instead. With \*(L"\fBaccuracy()\fR\*(R" you set the
number of digits each result should have, with \*(L"\fBprecision()\fR\*(R" you set the
place where to round.
.Sp
Please see the section about \*(L"\s-1ACCURACY\s0 and \s-1PRECISION\*(R"\s0 for further details.
.Sp
.Vb 4
\& $y = Math::BigInt\->new(1234567); # $y is not rounded
\& Math::BigInt\->precision(4); # set class precision to 4
\& $x = Math::BigInt\->new(1234567); # $x is rounded automatically
\& print $x; # prints "1230000"
.Ve
.Sp
Note: Each class has its 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.
.IP "\fBdiv_scale()\fR" 4
.IX Item "div_scale()"
Set/get the fallback accuracy. This is the accuracy used when neither accuracy
nor precision is set explicitly. It is used when a computation might otherwise
attempt to return an infinite number of digits.
.IP "\fBround_mode()\fR" 4
.IX Item "round_mode()"
Set/get the rounding mode.
.IP "\fBupgrade()\fR" 4
.IX Item "upgrade()"
Set/get the class for upgrading. When a computation might result in a
non-integer, the operands are upgraded to this class. This is used for instance
by bignum. The default is \f(CW\*(C`undef\*(C'\fR, thus the following operation creates
a Math::BigInt, not a Math::BigFloat:
.Sp
.Vb 2
\& my $i = Math::BigInt\->new(123);
\& my $f = Math::BigFloat\->new(\*(Aq123.1\*(Aq);
\&
\& print $i + $f, "\en"; # prints 246
.Ve
.IP "\fBdowngrade()\fR" 4
.IX Item "downgrade()"
Set/get the class for downgrading. The default is \f(CW\*(C`undef\*(C'\fR. Downgrading is not
done by Math::BigInt.
.IP "\fBmodify()\fR" 4
.IX Item "modify()"
.Vb 1
\& $x\->modify(\*(Aqbpowd\*(Aq);
.Ve
.Sp
This method returns 0 if the object can be modified with the given operation,
or 1 if not.
.Sp
This is used for instance by Math::BigInt::Constant.
.IP "\fBconfig()\fR" 4
.IX Item "config()"
.Vb 2
\& Math::BigInt\->config("trap_nan" => 1); # set
\& $accu = Math::BigInt\->config("accuracy"); # get
.Ve
.Sp
Set or get class variables. Read-only parameters are marked as \s-1RO.\s0 Read-write
parameters are marked as \s-1RW.\s0 The following parameters are supported.
.Sp
.Vb 10
\& Parameter RO/RW Description
\& Example
\& ============================================================
\& lib RO Name of the math backend library
\& Math::BigInt::Calc
\& lib_version RO Version of the math backend library
\& 0.30
\& class RO The class of config you just called
\& Math::BigRat
\& version RO version number of the class you used
\& 0.10
\& upgrade RW To which class numbers are upgraded
\& undef
\& downgrade RW To which class numbers are downgraded
\& undef
\& precision RW Global precision
\& undef
\& accuracy RW Global accuracy
\& undef
\& round_mode RW Global round mode
\& even
\& div_scale RW Fallback accuracy for division etc.
\& 40
\& trap_nan RW Trap NaNs
\& undef
\& trap_inf RW Trap +inf/\-inf
\& undef
.Ve
.SS "Constructor methods"
.IX Subsection "Constructor methods"
.IP "\fBnew()\fR" 4
.IX Item "new()"
.Vb 1
\& $x = Math::BigInt\->new($str,$A,$P,$R);
.Ve
.Sp
Creates a new Math::BigInt object from a scalar or another Math::BigInt object.
The input is accepted as decimal, hexadecimal (with leading '0x') or binary
(with leading '0b').
.Sp
See \*(L"Input\*(R" for more info on accepted input formats.
.IP "\fBfrom_hex()\fR" 4
.IX Item "from_hex()"
.Vb 1
\& $x = Math::BigInt\->from_hex("0xcafe"); # input is hexadecimal
.Ve
.Sp
Interpret input as a hexadecimal string. A \*(L"0x\*(R" or \*(L"x\*(R" prefix is optional. A
single underscore character may be placed right after the prefix, if present,
or between any two digits. If the input is invalid, a NaN is returned.
.IP "\fBfrom_oct()\fR" 4
.IX Item "from_oct()"
.Vb 1
\& $x = Math::BigInt\->from_oct("0775"); # input is octal
.Ve
.Sp
Interpret the input as an octal string and return the corresponding value. A
\&\*(L"0\*(R" (zero) prefix is optional. A single underscore character may be placed
right after the prefix, if present, or between any two digits. If the input is
invalid, a NaN is returned.
.IP "\fBfrom_bin()\fR" 4
.IX Item "from_bin()"
.Vb 1
\& $x = Math::BigInt\->from_bin("0b10011"); # input is binary
.Ve
.Sp
Interpret the input as a binary string. A \*(L"0b\*(R" or \*(L"b\*(R" prefix is optional. A
single underscore character may be placed right after the prefix, if present,
or between any two digits. If the input is invalid, a NaN is returned.
.IP "\fBfrom_bytes()\fR" 4
.IX Item "from_bytes()"
.Vb 1
\& $x = Math::BigInt\->from_bytes("\exf3\ex6b"); # $x = 62315
.Ve
.Sp
Interpret the input as a byte string, assuming big endian byte order. The
output is always a non-negative, finite integer.
.Sp
In some special cases, \fBfrom_bytes()\fR matches the conversion done by \fBunpack()\fR:
.Sp
.Vb 3
\& $b = "\ex4e"; # one char byte string
\& $x = Math::BigInt\->from_bytes($b); # = 78
\& $y = unpack "C", $b; # ditto, but scalar
\&
\& $b = "\exf3\ex6b"; # two char byte string
\& $x = Math::BigInt\->from_bytes($b); # = 62315
\& $y = unpack "S>", $b; # ditto, but scalar
\&
\& $b = "\ex2d\exe0\ex49\exad"; # four char byte string
\& $x = Math::BigInt\->from_bytes($b); # = 769673645
\& $y = unpack "L>", $b; # ditto, but scalar
\&
\& $b = "\ex2d\exe0\ex49\exad\ex2d\exe0\ex49\exad"; # eight char byte string
\& $x = Math::BigInt\->from_bytes($b); # = 3305723134637787565
\& $y = unpack "Q>", $b; # ditto, but scalar
.Ve
.IP "\fBfrom_base()\fR" 4
.IX Item "from_base()"
Given a string, a base, and an optional collation sequence, interpret the
string as a number in the given base. The collation sequence describes the
value of each character in the string.
.Sp
If a collation sequence is not given, a default collation sequence is used. If
the base is less than or equal to 36, the collation sequence is the string
consisting of the 36 characters \*(L"0\*(R" to \*(L"9\*(R" and \*(L"A\*(R" to \*(L"Z\*(R". In this case, the
letter case in the input is ignored. If the base is greater than 36, and
smaller than or equal to 62, the collation sequence is the string consisting of
the 62 characters \*(L"0\*(R" to \*(L"9\*(R", \*(L"A\*(R" to \*(L"Z\*(R", and \*(L"a\*(R" to \*(L"z\*(R". A base larger than 62
requires the collation sequence to be specified explicitly.
.Sp
These examples show standard binary, octal, and hexadecimal conversion. All
cases return 250.
.Sp
.Vb 3
\& $x = Math::BigInt\->from_base("11111010", 2);
\& $x = Math::BigInt\->from_base("372", 8);
\& $x = Math::BigInt\->from_base("fa", 16);
.Ve
.Sp
When the base is less than or equal to 36, and no collation sequence is given,
the letter case is ignored, so both of these also return 250:
.Sp
.Vb 2
\& $x = Math::BigInt\->from_base("6Y", 16);
\& $x = Math::BigInt\->from_base("6y", 16);
.Ve
.Sp
When the base greater than 36, and no collation sequence is given, the default
collation sequence contains both uppercase and lowercase letters, so
the letter case in the input is not ignored:
.Sp
.Vb 5
\& $x = Math::BigInt\->from_base("6S", 37); # $x is 250
\& $x = Math::BigInt\->from_base("6s", 37); # $x is 276
\& $x = Math::BigInt\->from_base("121", 3); # $x is 16
\& $x = Math::BigInt\->from_base("XYZ", 36); # $x is 44027
\& $x = Math::BigInt\->from_base("Why", 42); # $x is 58314
.Ve
.Sp
The collation sequence can be any set of unique characters. These two cases
are equivalent
.Sp
.Vb 2
\& $x = Math::BigInt\->from_base("100", 2, "01"); # $x is 4
\& $x = Math::BigInt\->from_base("|\-\-", 2, "\-|"); # $x is 4
.Ve
.IP "\fBbzero()\fR" 4
.IX Item "bzero()"
.Vb 2
\& $x = Math::BigInt\->bzero();
\& $x\->bzero();
.Ve
.Sp
Returns a new Math::BigInt object representing zero. If used as an instance
method, assigns the value to the invocand.
.IP "\fBbone()\fR" 4
.IX Item "bone()"
.Vb 6
\& $x = Math::BigInt\->bone(); # +1
\& $x = Math::BigInt\->bone("+"); # +1
\& $x = Math::BigInt\->bone("\-"); # \-1
\& $x\->bone(); # +1
\& $x\->bone("+"); # +1
\& $x\->bone(\*(Aq\-\*(Aq); # \-1
.Ve
.Sp
Creates a new Math::BigInt object representing one. The optional argument is
either '\-' or '+', indicating whether you want plus one or minus one. If used
as an instance method, assigns the value to the invocand.
.IP "\fBbinf()\fR" 4
.IX Item "binf()"
.Vb 1
\& $x = Math::BigInt\->binf($sign);
.Ve
.Sp
Creates a new Math::BigInt object representing infinity. The optional argument
is either '\-' or '+', indicating whether you want infinity or minus infinity.
If used as an instance method, assigns the value to the invocand.
.Sp
.Vb 2
\& $x\->binf();
\& $x\->binf(\*(Aq\-\*(Aq);
.Ve
.IP "\fBbnan()\fR" 4
.IX Item "bnan()"
.Vb 1
\& $x = Math::BigInt\->bnan();
.Ve
.Sp
Creates a new Math::BigInt object representing NaN (Not A Number). If used as
an instance method, assigns the value to the invocand.
.Sp
.Vb 1
\& $x\->bnan();
.Ve
.IP "\fBbpi()\fR" 4
.IX Item "bpi()"
.Vb 2
\& $x = Math::BigInt\->bpi(100); # 3
\& $x\->bpi(100); # 3
.Ve
.Sp
Creates a new Math::BigInt object representing \s-1PI.\s0 If used as an instance
method, assigns the value to the invocand. With Math::BigInt this always
returns 3.
.Sp
If upgrading is in effect, returns \s-1PI,\s0 rounded to N digits with the current
rounding mode:
.Sp
.Vb 4
\& use Math::BigFloat;
\& use Math::BigInt upgrade => "Math::BigFloat";
\& print Math::BigInt\->bpi(3), "\en"; # 3.14
\& print Math::BigInt\->bpi(100), "\en"; # 3.1415....
.Ve
.IP "\fBcopy()\fR" 4
.IX Item "copy()"
.Vb 1
\& $x\->copy(); # make a true copy of $x (unlike $y = $x)
.Ve
.IP "\fBas_int()\fR" 4
.IX Item "as_int()"
.PD 0
.IP "\fBas_number()\fR" 4
.IX Item "as_number()"
.PD
These methods are called when Math::BigInt encounters an object it doesn't know
how to handle. For instance, assume \f(CW$x\fR is a Math::BigInt, or subclass thereof,
and \f(CW$y\fR is defined, but not a Math::BigInt, or subclass thereof. If you do
.Sp
.Vb 1
\& $x \-> badd($y);
.Ve
.Sp
\&\f(CW$y\fR needs to be converted into an object that \f(CW$x\fR can deal with. This is done by
first checking if \f(CW$y\fR is something that \f(CW$x\fR might be upgraded to. If that is the
case, no further attempts are made. The next is to see if \f(CW$y\fR supports the
method \f(CW\*(C`as_int()\*(C'\fR. If it does, \f(CW\*(C`as_int()\*(C'\fR is called, but if it doesn't, the
next thing is to see if \f(CW$y\fR supports the method \f(CW\*(C`as_number()\*(C'\fR. If it does,
\&\f(CW\*(C`as_number()\*(C'\fR is called. The method \f(CW\*(C`as_int()\*(C'\fR (and \f(CW\*(C`as_number()\*(C'\fR) is
expected to return either an object that has the same class as \f(CW$x\fR, a subclass
thereof, or a string that \f(CW\*(C`ref($x)\->new()\*(C'\fR can parse to create an object.
.Sp
\&\f(CW\*(C`as_number()\*(C'\fR is an alias to \f(CW\*(C`as_int()\*(C'\fR. \f(CW\*(C`as_number\*(C'\fR was introduced in
v1.22, while \f(CW\*(C`as_int()\*(C'\fR was introduced in v1.68.
.Sp
In Math::BigInt, \f(CW\*(C`as_int()\*(C'\fR has the same effect as \f(CW\*(C`copy()\*(C'\fR.
.SS "Boolean methods"
.IX Subsection "Boolean methods"
None of these methods modify the invocand object.
.IP "\fBis_zero()\fR" 4
.IX Item "is_zero()"
.Vb 1
\& $x\->is_zero(); # true if $x is 0
.Ve
.Sp
Returns true if the invocand is zero and false otherwise.
.IP "is_one( [ \s-1SIGN\s0 ])" 4
.IX Item "is_one( [ SIGN ])"
.Vb 3
\& $x\->is_one(); # true if $x is +1
\& $x\->is_one("+"); # ditto
\& $x\->is_one("\-"); # true if $x is \-1
.Ve
.Sp
Returns true if the invocand is one and false otherwise.
.IP "\fBis_finite()\fR" 4
.IX Item "is_finite()"
.Vb 1
\& $x\->is_finite(); # true if $x is not +inf, \-inf or NaN
.Ve
.Sp
Returns true if the invocand is a finite number, i.e., it is neither +inf,
\&\-inf, nor NaN.
.IP "is_inf( [ \s-1SIGN\s0 ] )" 4
.IX Item "is_inf( [ SIGN ] )"
.Vb 3
\& $x\->is_inf(); # true if $x is +inf
\& $x\->is_inf("+"); # ditto
\& $x\->is_inf("\-"); # true if $x is \-inf
.Ve
.Sp
Returns true if the invocand is infinite and false otherwise.
.IP "\fBis_nan()\fR" 4
.IX Item "is_nan()"
.Vb 1
\& $x\->is_nan(); # true if $x is NaN
.Ve
.IP "\fBis_positive()\fR" 4
.IX Item "is_positive()"
.PD 0
.IP "\fBis_pos()\fR" 4
.IX Item "is_pos()"
.PD
.Vb 2
\& $x\->is_positive(); # true if > 0
\& $x\->is_pos(); # ditto
.Ve
.Sp
Returns true if the invocand is positive and false otherwise. A \f(CW\*(C`NaN\*(C'\fR is
neither positive nor negative.
.IP "\fBis_negative()\fR" 4
.IX Item "is_negative()"
.PD 0
.IP "\fBis_neg()\fR" 4
.IX Item "is_neg()"
.PD
.Vb 2
\& $x\->is_negative(); # true if < 0
\& $x\->is_neg(); # ditto
.Ve
.Sp
Returns true if the invocand is negative and false otherwise. A \f(CW\*(C`NaN\*(C'\fR is
neither positive nor negative.
.IP "\fBis_odd()\fR" 4
.IX Item "is_odd()"
.Vb 1
\& $x\->is_odd(); # true if odd, false for even
.Ve
.Sp
Returns true if the invocand is odd and false otherwise. \f(CW\*(C`NaN\*(C'\fR, \f(CW\*(C`+inf\*(C'\fR, and
\&\f(CW\*(C`\-inf\*(C'\fR are neither odd nor even.
.IP "\fBis_even()\fR" 4
.IX Item "is_even()"
.Vb 1
\& $x\->is_even(); # true if $x is even
.Ve
.Sp
Returns true if the invocand is even and false otherwise. \f(CW\*(C`NaN\*(C'\fR, \f(CW\*(C`+inf\*(C'\fR,
\&\f(CW\*(C`\-inf\*(C'\fR are not integers and are neither odd nor even.
.IP "\fBis_int()\fR" 4
.IX Item "is_int()"
.Vb 1
\& $x\->is_int(); # true if $x is an integer
.Ve
.Sp
Returns true if the invocand is an integer and false otherwise. \f(CW\*(C`NaN\*(C'\fR,
\&\f(CW\*(C`+inf\*(C'\fR, \f(CW\*(C`\-inf\*(C'\fR are not integers.
.SS "Comparison methods"
.IX Subsection "Comparison methods"
None of these methods modify the invocand object. Note that a \f(CW\*(C`NaN\*(C'\fR is neither
less than, greater than, or equal to anything else, even a \f(CW\*(C`NaN\*(C'\fR.
.IP "\fBbcmp()\fR" 4
.IX Item "bcmp()"
.Vb 1
\& $x\->bcmp($y);
.Ve
.Sp
Returns \-1, 0, 1 depending on whether \f(CW$x\fR is less than, equal to, or grater than
\&\f(CW$y\fR. Returns undef if any operand is a NaN.
.IP "\fBbacmp()\fR" 4
.IX Item "bacmp()"
.Vb 1
\& $x\->bacmp($y);
.Ve
.Sp
Returns \-1, 0, 1 depending on whether the absolute value of \f(CW$x\fR is less than,
equal to, or grater than the absolute value of \f(CW$y\fR. Returns undef if any operand
is a NaN.
.IP "\fBbeq()\fR" 4
.IX Item "beq()"
.Vb 1
\& $x \-> beq($y);
.Ve
.Sp
Returns true if and only if \f(CW$x\fR is equal to \f(CW$y\fR, and false otherwise.
.IP "\fBbne()\fR" 4
.IX Item "bne()"
.Vb 1
\& $x \-> bne($y);
.Ve
.Sp
Returns true if and only if \f(CW$x\fR is not equal to \f(CW$y\fR, and false otherwise.
.IP "\fBblt()\fR" 4
.IX Item "blt()"
.Vb 1
\& $x \-> blt($y);
.Ve
.Sp
Returns true if and only if \f(CW$x\fR is equal to \f(CW$y\fR, and false otherwise.
.IP "\fBble()\fR" 4
.IX Item "ble()"
.Vb 1
\& $x \-> ble($y);
.Ve
.Sp
Returns true if and only if \f(CW$x\fR is less than or equal to \f(CW$y\fR, and false
otherwise.
.IP "\fBbgt()\fR" 4
.IX Item "bgt()"
.Vb 1
\& $x \-> bgt($y);
.Ve
.Sp
Returns true if and only if \f(CW$x\fR is greater than \f(CW$y\fR, and false otherwise.
.IP "\fBbge()\fR" 4
.IX Item "bge()"
.Vb 1
\& $x \-> bge($y);
.Ve
.Sp
Returns true if and only if \f(CW$x\fR is greater than or equal to \f(CW$y\fR, and false
otherwise.
.SS "Arithmetic methods"
.IX Subsection "Arithmetic methods"
These methods modify the invocand object and returns it.
.IP "\fBbneg()\fR" 4
.IX Item "bneg()"
.Vb 1
\& $x\->bneg();
.Ve
.Sp
Negate the number, e.g. change the sign between '+' and '\-', or between '+inf'
and '\-inf', respectively. Does nothing for NaN or zero.
.IP "\fBbabs()\fR" 4
.IX Item "babs()"
.Vb 1
\& $x\->babs();
.Ve
.Sp
Set the number to its absolute value, e.g. change the sign from '\-' to '+'
and from '\-inf' to '+inf', respectively. Does nothing for NaN or positive
numbers.
.IP "\fBbsgn()\fR" 4
.IX Item "bsgn()"
.Vb 1
\& $x\->bsgn();
.Ve
.Sp
Signum function. Set the number to \-1, 0, or 1, depending on whether the
number is negative, zero, or positive, respectively. Does not modify NaNs.
.IP "\fBbnorm()\fR" 4
.IX Item "bnorm()"
.Vb 1
\& $x\->bnorm(); # normalize (no\-op)
.Ve
.Sp
Normalize the number. This is a no-op and is provided only for backwards
compatibility.
.IP "\fBbinc()\fR" 4
.IX Item "binc()"
.Vb 1
\& $x\->binc(); # increment x by 1
.Ve
.IP "\fBbdec()\fR" 4
.IX Item "bdec()"
.Vb 1
\& $x\->bdec(); # decrement x by 1
.Ve
.IP "\fBbadd()\fR" 4
.IX Item "badd()"
.Vb 1
\& $x\->badd($y); # addition (add $y to $x)
.Ve
.IP "\fBbsub()\fR" 4
.IX Item "bsub()"
.Vb 1
\& $x\->bsub($y); # subtraction (subtract $y from $x)
.Ve
.IP "\fBbmul()\fR" 4
.IX Item "bmul()"
.Vb 1
\& $x\->bmul($y); # multiplication (multiply $x by $y)
.Ve
.IP "\fBbmuladd()\fR" 4
.IX Item "bmuladd()"
.Vb 1
\& $x\->bmuladd($y,$z);
.Ve
.Sp
Multiply \f(CW$x\fR by \f(CW$y\fR, and then add \f(CW$z\fR to the result,
.Sp
This method was added in v1.87 of Math::BigInt (June 2007).
.IP "\fBbdiv()\fR" 4
.IX Item "bdiv()"
.Vb 1
\& $x\->bdiv($y); # divide, set $x to quotient
.Ve
.Sp
Divides \f(CW$x\fR by \f(CW$y\fR by doing floored division (F\-division), where the quotient is
the floored (rounded towards negative infinity) quotient of the two operands.
In list context, returns the quotient and the remainder. The remainder is
either zero or has the same sign as the second operand. In scalar context, only
the quotient is returned.
.Sp
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
non-zero) always has the same sign as the second operand; so, for example,
.Sp
.Vb 6
\& 1 / 4 => ( 0, 1)
\& 1 / \-4 => (\-1, \-3)
\& \-3 / 4 => (\-1, 1)
\& \-3 / \-4 => ( 0, \-3)
\& \-11 / 2 => (\-5, 1)
\& 11 / \-2 => (\-5, \-1)
.Ve
.Sp
The behavior of the overloaded operator % agrees with the behavior of Perl's
built-in % operator (as documented in the perlop manpage), and the equation
.Sp
.Vb 1
\& $x == ($x / $y) * $y + ($x % $y)
.Ve
.Sp
holds true for any finite \f(CW$x\fR and finite, non-zero \f(CW$y\fR.
.Sp
Perl's \*(L"use integer\*(R" might change the behaviour of % and / for scalars. This is
because under 'use integer' Perl does what the underlying C library thinks is
right, and this varies. However, \*(L"use integer\*(R" does not change the way things
are done with Math::BigInt objects.
.IP "\fBbtdiv()\fR" 4
.IX Item "btdiv()"
.Vb 1
\& $x\->btdiv($y); # divide, set $x to quotient
.Ve
.Sp
Divides \f(CW$x\fR by \f(CW$y\fR by doing truncated division (T\-division), where quotient is
the truncated (rouneded towards zero) quotient of the two operands. In list
context, returns the quotient and the remainder. The remainder is either zero
or has the same sign as the first operand. In scalar context, only the quotient
is returned.
.IP "\fBbmod()\fR" 4
.IX Item "bmod()"
.Vb 1
\& $x\->bmod($y); # modulus (x % y)
.Ve
.Sp
Returns \f(CW$x\fR modulo \f(CW$y\fR, i.e., the remainder after floored division (F\-division).
This method is like Perl's % operator. See \*(L"\fBbdiv()\fR\*(R".
.IP "\fBbtmod()\fR" 4
.IX Item "btmod()"
.Vb 1
\& $x\->btmod($y); # modulus
.Ve
.Sp
Returns the remainer after truncated division (T\-division). See \*(L"\fBbtdiv()\fR\*(R".
.IP "\fBbmodinv()\fR" 4
.IX Item "bmodinv()"
.Vb 1
\& $x\->bmodinv($mod); # modular multiplicative inverse
.Ve
.Sp
Returns the multiplicative inverse of \f(CW$x\fR modulo \f(CW$mod\fR. If
.Sp
.Vb 1
\& $y = $x \-> copy() \-> bmodinv($mod)
.Ve
.Sp
then \f(CW$y\fR is the number closest to zero, and with the same sign as \f(CW$mod\fR,
satisfying
.Sp
.Vb 1
\& ($x * $y) % $mod = 1 % $mod
.Ve
.Sp
If \f(CW$x\fR and \f(CW$y\fR are non-zero, they must be relative primes, i.e.,
\&\f(CW\*(C`bgcd($y, $mod)==1\*(C'\fR. '\f(CW\*(C`NaN\*(C'\fR' is returned when no modular multiplicative
inverse exists.
.IP "\fBbmodpow()\fR" 4
.IX Item "bmodpow()"
.Vb 2
\& $num\->bmodpow($exp,$mod); # modular exponentiation
\& # ($num**$exp % $mod)
.Ve
.Sp
Returns the value of \f(CW$num\fR taken to the power \f(CW$exp\fR in the modulus
\&\f(CW$mod\fR using binary exponentiation. \f(CW\*(C`bmodpow\*(C'\fR is far superior to
writing
.Sp
.Vb 1
\& $num ** $exp % $mod
.Ve
.Sp
because it is much faster \- it reduces internal variables into
the modulus whenever possible, so it operates on smaller numbers.
.Sp
\&\f(CW\*(C`bmodpow\*(C'\fR also supports negative exponents.
.Sp
.Vb 1
\& bmodpow($num, \-1, $mod)
.Ve
.Sp
is exactly equivalent to
.Sp
.Vb 1
\& bmodinv($num, $mod)
.Ve
.IP "\fBbpow()\fR" 4
.IX Item "bpow()"
.Vb 1
\& $x\->bpow($y); # power of arguments (x ** y)
.Ve
.Sp
\&\f(CW\*(C`bpow()\*(C'\fR (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 \f(CW\*(C`badd()\*(C'\fR etc. The first three modifies
\&\f(CW$x\fR, the last one won't:
.Sp
.Vb 4
\& print bpow($x,$i),"\en"; # modify $x
\& print $x\->bpow($i),"\en"; # ditto
\& print $x **= $i,"\en"; # the same
\& print $x ** $i,"\en"; # leave $x alone
.Ve
.Sp
The form \f(CW\*(C`$x **= $y\*(C'\fR is faster than \f(CW\*(C`$x = $x ** $y;\*(C'\fR, though.
.IP "\fBblog()\fR" 4
.IX Item "blog()"
.Vb 1
\& $x\->blog($base, $accuracy); # logarithm of x to the base $base
.Ve
.Sp
If \f(CW$base\fR is not defined, Euler's number (e) is used:
.Sp
.Vb 1
\& print $x\->blog(undef, 100); # log(x) to 100 digits
.Ve
.IP "\fBbexp()\fR" 4
.IX Item "bexp()"
.Vb 1
\& $x\->bexp($accuracy); # calculate e ** X
.Ve
.Sp
Calculates the expression \f(CW\*(C`e ** $x\*(C'\fR where \f(CW\*(C`e\*(C'\fR is Euler's number.
.Sp
This method was added in v1.82 of Math::BigInt (April 2007).
.Sp
See also \*(L"\fBblog()\fR\*(R".
.IP "\fBbnok()\fR" 4
.IX Item "bnok()"
.Vb 1
\& $x\->bnok($y); # x over y (binomial coefficient n over k)
.Ve
.Sp
Calculates the binomial coefficient n over k, also called the \*(L"choose\*(R"
function, which is
.Sp
.Vb 3
\& ( n ) n!
\& | | = \-\-\-\-\-\-\-\-
\& ( k ) k!(n\-k)!
.Ve
.Sp
when n and k are non-negative. This method implements the full Kronenburg
extension (Kronenburg, M.J. \*(L"The Binomial Coefficient for Negative Arguments.\*(R"
18 May 2011. http://arxiv.org/abs/1105.3689/) illustrated by the following
pseudo-code:
.Sp
.Vb 8
\& if n >= 0 and k >= 0:
\& return binomial(n, k)
\& if k >= 0:
\& return (\-1)^k*binomial(\-n+k\-1, k)
\& if k <= n:
\& return (\-1)^(n\-k)*binomial(\-k\-1, n\-k)
\& else
\& return 0
.Ve
.Sp
The behaviour is identical to the behaviour of the Maple and Mathematica
function for negative integers n, k.
.IP "\fBbsin()\fR" 4
.IX Item "bsin()"
.Vb 2
\& my $x = Math::BigInt\->new(1);
\& print $x\->bsin(100), "\en";
.Ve
.Sp
Calculate the sine of \f(CW$x\fR, modifying \f(CW$x\fR in place.
.Sp
In Math::BigInt, unless upgrading is in effect, the result is truncated to an
integer.
.Sp
This method was added in v1.87 of Math::BigInt (June 2007).
.IP "\fBbcos()\fR" 4
.IX Item "bcos()"
.Vb 2
\& my $x = Math::BigInt\->new(1);
\& print $x\->bcos(100), "\en";
.Ve
.Sp
Calculate the cosine of \f(CW$x\fR, modifying \f(CW$x\fR in place.
.Sp
In Math::BigInt, unless upgrading is in effect, the result is truncated to an
integer.
.Sp
This method was added in v1.87 of Math::BigInt (June 2007).
.IP "\fBbatan()\fR" 4
.IX Item "batan()"
.Vb 2
\& my $x = Math::BigFloat\->new(0.5);
\& print $x\->batan(100), "\en";
.Ve
.Sp
Calculate the arcus tangens of \f(CW$x\fR, modifying \f(CW$x\fR in place.
.Sp
In Math::BigInt, unless upgrading is in effect, the result is truncated to an
integer.
.Sp
This method was added in v1.87 of Math::BigInt (June 2007).
.IP "\fBbatan2()\fR" 4
.IX Item "batan2()"
.Vb 3
\& my $x = Math::BigInt\->new(1);
\& my $y = Math::BigInt\->new(1);
\& print $y\->batan2($x), "\en";
.Ve
.Sp
Calculate the arcus tangens of \f(CW$y\fR divided by \f(CW$x\fR, modifying \f(CW$y\fR in place.
.Sp
In Math::BigInt, unless upgrading is in effect, the result is truncated to an
integer.
.Sp
This method was added in v1.87 of Math::BigInt (June 2007).
.IP "\fBbsqrt()\fR" 4
.IX Item "bsqrt()"
.Vb 1
\& $x\->bsqrt(); # calculate square root
.Ve
.Sp
\&\f(CW\*(C`bsqrt()\*(C'\fR returns the square root truncated to an integer.
.Sp
If you want a better approximation of the square root, then use:
.Sp
.Vb 4
\& $x = Math::BigFloat\->new(12);
\& Math::BigFloat\->precision(0);
\& Math::BigFloat\->round_mode(\*(Aqeven\*(Aq);
\& print $x\->copy\->bsqrt(),"\en"; # 4
\&
\& Math::BigFloat\->precision(2);
\& print $x\->bsqrt(),"\en"; # 3.46
\& print $x\->bsqrt(3),"\en"; # 3.464
.Ve
.IP "\fBbroot()\fR" 4
.IX Item "broot()"
.Vb 1
\& $x\->broot($N);
.Ve
.Sp
Calculates the N'th root of \f(CW$x\fR.
.IP "\fBbfac()\fR" 4
.IX Item "bfac()"
.Vb 1
\& $x\->bfac(); # factorial of $x (1*2*3*4*..*$x)
.Ve
.Sp
Returns the factorial of \f(CW$x\fR, i.e., the product of all positive integers up
to and including \f(CW$x\fR.
.IP "\fBbdfac()\fR" 4
.IX Item "bdfac()"
.Vb 1
\& $x\->bdfac(); # double factorial of $x (1*2*3*4*..*$x)
.Ve
.Sp
Returns the double factorial of \f(CW$x\fR. If \f(CW$x\fR is an even integer, returns the
product of all positive, even integers up to and including \f(CW$x\fR, i.e.,
2*4*6*...*$x. If \f(CW$x\fR is an odd integer, returns the product of all positive,
odd integers, i.e., 1*3*5*...*$x.
.IP "\fBbfib()\fR" 4
.IX Item "bfib()"
.Vb 2
\& $F = $n\->bfib(); # a single Fibonacci number
\& @F = $n\->bfib(); # a list of Fibonacci numbers
.Ve
.Sp
In scalar context, returns a single Fibonacci number. In list context, returns
a list of Fibonacci numbers. The invocand is the last element in the output.
.Sp
The Fibonacci sequence is defined by
.Sp
.Vb 3
\& F(0) = 0
\& F(1) = 1
\& F(n) = F(n\-1) + F(n\-2)
.Ve
.Sp
In list context, F(0) and F(n) is the first and last number in the output,
respectively. For example, if \f(CW$n\fR is 12, then \f(CW\*(C`@F = $n\->bfib()\*(C'\fR returns the
following values, F(0) to F(12):
.Sp
.Vb 1
\& 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144
.Ve
.Sp
The sequence can also be extended to negative index n using the re-arranged
recurrence relation
.Sp
.Vb 1
\& F(n\-2) = F(n) \- F(n\-1)
.Ve
.Sp
giving the bidirectional sequence
.Sp
.Vb 2
\& n \-7 \-6 \-5 \-4 \-3 \-2 \-1 0 1 2 3 4 5 6 7
\& F(n) 13 \-8 5 \-3 2 \-1 1 0 1 1 2 3 5 8 13
.Ve
.Sp
If \f(CW$n\fR is \-12, the following values, F(0) to F(12), are returned:
.Sp
.Vb 1
\& 0, 1, \-1, 2, \-3, 5, \-8, 13, \-21, 34, \-55, 89, \-144
.Ve
.IP "\fBblucas()\fR" 4
.IX Item "blucas()"
.Vb 2
\& $F = $n\->blucas(); # a single Lucas number
\& @F = $n\->blucas(); # a list of Lucas numbers
.Ve
.Sp
In scalar context, returns a single Lucas number. In list context, returns a
list of Lucas numbers. The invocand is the last element in the output.
.Sp
The Lucas sequence is defined by
.Sp
.Vb 3
\& L(0) = 2
\& L(1) = 1
\& L(n) = L(n\-1) + L(n\-2)
.Ve
.Sp
In list context, L(0) and L(n) is the first and last number in the output,
respectively. For example, if \f(CW$n\fR is 12, then \f(CW\*(C`@L = $n\->blucas()\*(C'\fR returns
the following values, L(0) to L(12):
.Sp
.Vb 1
\& 2, 1, 3, 4, 7, 11, 18, 29, 47, 76, 123, 199, 322
.Ve
.Sp
The sequence can also be extended to negative index n using the re-arranged
recurrence relation
.Sp
.Vb 1
\& L(n\-2) = L(n) \- L(n\-1)
.Ve
.Sp
giving the bidirectional sequence
.Sp
.Vb 2
\& n \-7 \-6 \-5 \-4 \-3 \-2 \-1 0 1 2 3 4 5 6 7
\& L(n) 29 \-18 11 \-7 4 \-3 1 2 1 3 4 7 11 18 29
.Ve
.Sp
If \f(CW$n\fR is \-12, the following values, L(0) to L(\-12), are returned:
.Sp
.Vb 1
\& 2, 1, \-3, 4, \-7, 11, \-18, 29, \-47, 76, \-123, 199, \-322
.Ve
.IP "\fBbrsft()\fR" 4
.IX Item "brsft()"
.Vb 2
\& $x\->brsft($n); # right shift $n places in base 2
\& $x\->brsft($n, $b); # right shift $n places in base $b
.Ve
.Sp
The latter is equivalent to
.Sp
.Vb 1
\& $x \-> bdiv($b \-> copy() \-> bpow($n))
.Ve
.IP "\fBblsft()\fR" 4
.IX Item "blsft()"
.Vb 2
\& $x\->blsft($n); # left shift $n places in base 2
\& $x\->blsft($n, $b); # left shift $n places in base $b
.Ve
.Sp
The latter is equivalent to
.Sp
.Vb 1
\& $x \-> bmul($b \-> copy() \-> bpow($n))
.Ve
.SS "Bitwise methods"
.IX Subsection "Bitwise methods"
.IP "\fBband()\fR" 4
.IX Item "band()"
.Vb 1
\& $x\->band($y); # bitwise and
.Ve
.IP "\fBbior()\fR" 4
.IX Item "bior()"
.Vb 1
\& $x\->bior($y); # bitwise inclusive or
.Ve
.IP "\fBbxor()\fR" 4
.IX Item "bxor()"
.Vb 1
\& $x\->bxor($y); # bitwise exclusive or
.Ve
.IP "\fBbnot()\fR" 4
.IX Item "bnot()"
.Vb 1
\& $x\->bnot(); # bitwise not (two\*(Aqs complement)
.Ve
.Sp
Two's complement (bitwise not). This is equivalent to, but faster than,
.Sp
.Vb 1
\& $x\->binc()\->bneg();
.Ve
.SS "Rounding methods"
.IX Subsection "Rounding methods"
.IP "\fBround()\fR" 4
.IX Item "round()"
.Vb 1
\& $x\->round($A,$P,$round_mode);
.Ve
.Sp
Round \f(CW$x\fR to accuracy \f(CW$A\fR or precision \f(CW$P\fR using the round mode
\&\f(CW$round_mode\fR.
.IP "\fBbround()\fR" 4
.IX Item "bround()"
.Vb 1
\& $x\->bround($N); # accuracy: preserve $N digits
.Ve
.Sp
Rounds \f(CW$x\fR to an accuracy of \f(CW$N\fR digits.
.IP "\fBbfround()\fR" 4
.IX Item "bfround()"
.Vb 1
\& $x\->bfround($N);
.Ve
.Sp
Rounds to a multiple of 10**$N. Examples:
.Sp
.Vb 1
\& Input N Result
\&
\& 123456.123456 3 123500
\& 123456.123456 2 123450
\& 123456.123456 \-2 123456.12
\& 123456.123456 \-3 123456.123
.Ve
.IP "\fBbfloor()\fR" 4
.IX Item "bfloor()"
.Vb 1
\& $x\->bfloor();
.Ve
.Sp
Round \f(CW$x\fR towards minus infinity, i.e., set \f(CW$x\fR to the largest integer less than
or equal to \f(CW$x\fR.
.IP "\fBbceil()\fR" 4
.IX Item "bceil()"
.Vb 1
\& $x\->bceil();
.Ve
.Sp
Round \f(CW$x\fR towards plus infinity, i.e., set \f(CW$x\fR to the smallest integer greater
than or equal to \f(CW$x\fR).
.IP "\fBbint()\fR" 4
.IX Item "bint()"
.Vb 1
\& $x\->bint();
.Ve
.Sp
Round \f(CW$x\fR towards zero.
.SS "Other mathematical methods"
.IX Subsection "Other mathematical methods"
.IP "\fBbgcd()\fR" 4
.IX Item "bgcd()"
.Vb 2
\& $x \-> bgcd($y); # GCD of $x and $y
\& $x \-> bgcd($y, $z, ...); # GCD of $x, $y, $z, ...
.Ve
.Sp
Returns the greatest common divisor (\s-1GCD\s0).
.IP "\fBblcm()\fR" 4
.IX Item "blcm()"
.Vb 2
\& $x \-> blcm($y); # LCM of $x and $y
\& $x \-> blcm($y, $z, ...); # LCM of $x, $y, $z, ...
.Ve
.Sp
Returns the least common multiple (\s-1LCM\s0).
.SS "Object property methods"
.IX Subsection "Object property methods"
.IP "\fBsign()\fR" 4
.IX Item "sign()"
.Vb 1
\& $x\->sign();
.Ve
.Sp
Return the sign, of \f(CW$x\fR, meaning either \f(CW\*(C`+\*(C'\fR, \f(CW\*(C`\-\*(C'\fR, \f(CW\*(C`\-inf\*(C'\fR, \f(CW\*(C`+inf\*(C'\fR or NaN.
.Sp
If you want \f(CW$x\fR to have a certain sign, use one of the following methods:
.Sp
.Vb 5
\& $x\->babs(); # \*(Aq+\*(Aq
\& $x\->babs()\->bneg(); # \*(Aq\-\*(Aq
\& $x\->bnan(); # \*(AqNaN\*(Aq
\& $x\->binf(); # \*(Aq+inf\*(Aq
\& $x\->binf(\*(Aq\-\*(Aq); # \*(Aq\-inf\*(Aq
.Ve
.IP "\fBdigit()\fR" 4
.IX Item "digit()"
.Vb 1
\& $x\->digit($n); # return the nth digit, counting from right
.Ve
.Sp
If \f(CW$n\fR is negative, returns the digit counting from left.
.IP "\fBlength()\fR" 4
.IX Item "length()"
.Vb 2
\& $x\->length();
\& ($xl, $fl) = $x\->length();
.Ve
.Sp
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
Math::BigInt objects, the length of the fraction part is always 0.
.Sp
The following probably doesn't do what you expect:
.Sp
.Vb 2
\& $c = Math::BigInt\->new(123);
\& print $c\->length(),"\en"; # prints 30
.Ve
.Sp
It prints both the number of digits in the number and in the fraction part
since print calls \f(CW\*(C`length()\*(C'\fR in list context. Use something like:
.Sp
.Vb 1
\& print scalar $c\->length(),"\en"; # prints 3
.Ve
.IP "\fBmantissa()\fR" 4
.IX Item "mantissa()"
.Vb 1
\& $x\->mantissa();
.Ve
.Sp
Return the signed mantissa of \f(CW$x\fR as a Math::BigInt.
.IP "\fBexponent()\fR" 4
.IX Item "exponent()"
.Vb 1
\& $x\->exponent();
.Ve
.Sp
Return the exponent of \f(CW$x\fR as a Math::BigInt.
.IP "\fBparts()\fR" 4
.IX Item "parts()"
.Vb 1
\& $x\->parts();
.Ve
.Sp
Returns the significand (mantissa) and the exponent as integers. In
Math::BigFloat, both are returned as Math::BigInt objects.
.IP "\fBsparts()\fR" 4
.IX Item "sparts()"
Returns the significand (mantissa) and the exponent as integers. In scalar
context, only the significand is returned. The significand is the integer with
the smallest absolute value. The output of \f(CW\*(C`sparts()\*(C'\fR corresponds to the
output from \f(CW\*(C`bsstr()\*(C'\fR.
.Sp
In Math::BigInt, this method is identical to \f(CW\*(C`parts()\*(C'\fR.
.IP "\fBnparts()\fR" 4
.IX Item "nparts()"
Returns the significand (mantissa) and exponent corresponding to normalized
notation. In scalar context, only the significand is returned. For finite
non-zero numbers, the significand's absolute value is greater than or equal to
1 and less than 10. The output of \f(CW\*(C`nparts()\*(C'\fR corresponds to the output from
\&\f(CW\*(C`bnstr()\*(C'\fR. In Math::BigInt, if the significand can not be represented as an
integer, upgrading is performed or NaN is returned.
.IP "\fBeparts()\fR" 4
.IX Item "eparts()"
Returns the significand (mantissa) and exponent corresponding to engineering
notation. In scalar context, only the significand is returned. For finite
non-zero numbers, the significand's absolute value is greater than or equal to
1 and less than 1000, and the exponent is a multiple of 3. The output of
\&\f(CW\*(C`eparts()\*(C'\fR corresponds to the output from \f(CW\*(C`bestr()\*(C'\fR. In Math::BigInt, if the
significand can not be represented as an integer, upgrading is performed or NaN
is returned.
.IP "\fBdparts()\fR" 4
.IX Item "dparts()"
Returns the integer part and the fraction part. If the fraction part can not be
represented as an integer, upgrading is performed or NaN is returned. The
output of \f(CW\*(C`dparts()\*(C'\fR corresponds to the output from \f(CW\*(C`bdstr()\*(C'\fR.
.SS "String conversion methods"
.IX Subsection "String conversion methods"
.IP "\fBbstr()\fR" 4
.IX Item "bstr()"
Returns a string representing the number using decimal notation. In
Math::BigFloat, the output is zero padded according to the current accuracy or
precision, if any of those are defined.
.IP "\fBbsstr()\fR" 4
.IX Item "bsstr()"
Returns a string representing the number using scientific notation where both
the significand (mantissa) and the exponent are integers. The output
corresponds to the output from \f(CW\*(C`sparts()\*(C'\fR.
.Sp
.Vb 5
\& 123 is returned as "123e+0"
\& 1230 is returned as "123e+1"
\& 12300 is returned as "123e+2"
\& 12000 is returned as "12e+3"
\& 10000 is returned as "1e+4"
.Ve
.IP "\fBbnstr()\fR" 4
.IX Item "bnstr()"
Returns a string representing the number using normalized notation, the most
common variant of scientific notation. For finite non-zero numbers, the
absolute value of the significand is greater than or equal to 1 and less than
10. The output corresponds to the output from \f(CW\*(C`nparts()\*(C'\fR.
.Sp
.Vb 5
\& 123 is returned as "1.23e+2"
\& 1230 is returned as "1.23e+3"
\& 12300 is returned as "1.23e+4"
\& 12000 is returned as "1.2e+4"
\& 10000 is returned as "1e+4"
.Ve
.IP "\fBbestr()\fR" 4
.IX Item "bestr()"
Returns a string representing the number using engineering notation. For finite
non-zero numbers, the absolute value of the significand is greater than or
equal to 1 and less than 1000, and the exponent is a multiple of 3. The output
corresponds to the output from \f(CW\*(C`eparts()\*(C'\fR.
.Sp
.Vb 5
\& 123 is returned as "123e+0"
\& 1230 is returned as "1.23e+3"
\& 12300 is returned as "12.3e+3"
\& 12000 is returned as "12e+3"
\& 10000 is returned as "10e+3"
.Ve
.IP "\fBbdstr()\fR" 4
.IX Item "bdstr()"
Returns a string representing the number using decimal notation. The output
corresponds to the output from \f(CW\*(C`dparts()\*(C'\fR.
.Sp
.Vb 5
\& 123 is returned as "123"
\& 1230 is returned as "1230"
\& 12300 is returned as "12300"
\& 12000 is returned as "12000"
\& 10000 is returned as "10000"
.Ve
.IP "\fBto_hex()\fR" 4
.IX Item "to_hex()"
.Vb 1
\& $x\->to_hex();
.Ve
.Sp
Returns a hexadecimal string representation of the number. See also \fBfrom_hex()\fR.
.IP "\fBto_bin()\fR" 4
.IX Item "to_bin()"
.Vb 1
\& $x\->to_bin();
.Ve
.Sp
Returns a binary string representation of the number. See also \fBfrom_bin()\fR.
.IP "\fBto_oct()\fR" 4
.IX Item "to_oct()"
.Vb 1
\& $x\->to_oct();
.Ve
.Sp
Returns an octal string representation of the number. See also \fBfrom_oct()\fR.
.IP "\fBto_bytes()\fR" 4
.IX Item "to_bytes()"
.Vb 2
\& $x = Math::BigInt\->new("1667327589");
\& $s = $x\->to_bytes(); # $s = "cafe"
.Ve
.Sp
Returns a byte string representation of the number using big endian byte
order. The invocand must be a non-negative, finite integer. See also \fBfrom_bytes()\fR.
.IP "\fBto_base()\fR" 4
.IX Item "to_base()"
.Vb 4
\& $x = Math::BigInt\->new("250");
\& $x\->to_base(2); # returns "11111010"
\& $x\->to_base(8); # returns "372"
\& $x\->to_base(16); # returns "fa"
.Ve
.Sp
Returns a string representation of the number in the given base. If a collation
sequence is given, the collation sequence determines which characters are used
in the output.
.Sp
Here are some more examples
.Sp
.Vb 4
\& $x = Math::BigInt\->new("16")\->to_base(3); # returns "121"
\& $x = Math::BigInt\->new("44027")\->to_base(36); # returns "XYZ"
\& $x = Math::BigInt\->new("58314")\->to_base(42); # returns "Why"
\& $x = Math::BigInt\->new("4")\->to_base(2, "\-|"); # returns "|\-\-"
.Ve
.Sp
See \fBfrom_base()\fR for information and examples.
.IP "\fBas_hex()\fR" 4
.IX Item "as_hex()"
.Vb 1
\& $x\->as_hex();
.Ve
.Sp
As, \f(CW\*(C`to_hex()\*(C'\fR, but with a \*(L"0x\*(R" prefix.
.IP "\fBas_bin()\fR" 4
.IX Item "as_bin()"
.Vb 1
\& $x\->as_bin();
.Ve
.Sp
As, \f(CW\*(C`to_bin()\*(C'\fR, but with a \*(L"0b\*(R" prefix.
.IP "\fBas_oct()\fR" 4
.IX Item "as_oct()"
.Vb 1
\& $x\->as_oct();
.Ve
.Sp
As, \f(CW\*(C`to_oct()\*(C'\fR, but with a \*(L"0\*(R" prefix.
.IP "\fBas_bytes()\fR" 4
.IX Item "as_bytes()"
This is just an alias for \f(CW\*(C`to_bytes()\*(C'\fR.
.SS "Other conversion methods"
.IX Subsection "Other conversion methods"
.IP "\fBnumify()\fR" 4
.IX Item "numify()"
.Vb 1
\& print $x\->numify();
.Ve
.Sp
Returns a Perl scalar from \f(CW$x\fR. It is used automatically whenever a scalar is
needed, for instance in array index operations.
.SH "ACCURACY and PRECISION"
.IX Header "ACCURACY and PRECISION"
Math::BigInt and Math::BigFloat have full support for accuracy and precision
based rounding, both automatically after every operation, as well as manually.
.PP
This section describes the accuracy/precision handling in Math::BigInt and
Math::BigFloat as it used to be and as it is now, complete with an explanation
of all terms and abbreviations.
.PP
Not yet implemented things (but with correct description) are marked with '!',
things that need to be answered are marked with '?'.
.PP
In the next paragraph follows a short description of terms used here (because
these may differ from terms used by others people or documentation).
.PP
During the rest of this document, the shortcuts A (for accuracy), P (for
precision), F (fallback) and R (rounding mode) are be used.
.SS "Precision P"
.IX Subsection "Precision P"
Precision is a fixed number of digits before (positive) or after (negative) the
decimal point. For example, 123.45 has a precision of \-2. 0 means an integer
like 123 (or 120). A precision of 2 means at least 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 different precisions, because 1200
can have P = 0, 1 or 2 (depending on what the initial value was). It could also
have p < 0, when the digits after the decimal point are zero.
.PP
The string output (of floating point numbers) is padded with zeros:
.PP
.Vb 9
\& 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
.Ve
.PP
For Math::BigInt objects, no padding occurs.
.SS "Accuracy A"
.IX Subsection "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,
123.45000 has 8 and 0.000123 has 3.
.PP
The string output (of floating point numbers) is padded with zeros:
.PP
.Vb 5
\& 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
.Ve
.PP
For Math::BigInt objects, no padding occurs.
.SS "Fallback F"
.IX Subsection "Fallback F"
When both A and P are undefined, this is used as a fallback accuracy when
dividing numbers.
.SS "Rounding mode R"
.IX Subsection "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.)
.PP
\fIDirected rounding\fR
.IX Subsection "Directed rounding"
.PP
These round modes always round in the same direction.
.IP "'trunc'" 4
.IX Item "'trunc'"
Round towards zero. Remove all digits following the rounding place, i.e.,
replace them with zeros. Thus, 987.65 rounded to tens (P=1) becomes 980, and
rounded to the fourth significant digit becomes 987.6 (A=4). 123.456 rounded to
the second place after the decimal point (P=\-2) becomes 123.46. This
corresponds to the \s-1IEEE 754\s0 rounding mode 'roundTowardZero'.
.PP
\fIRounding to nearest\fR
.IX Subsection "Rounding to nearest"
.PP
These rounding modes round to the nearest digit. They differ in how they
determine which way to round in the ambiguous case when there is a tie.
.IP "'even'" 4
.IX Item "'even'"
Round towards the nearest even digit, e.g., when rounding to nearest integer,
\&\-5.5 becomes \-6, 4.5 becomes 4, but 4.501 becomes 5. This corresponds to the
\&\s-1IEEE 754\s0 rounding mode 'roundTiesToEven'.
.IP "'odd'" 4
.IX Item "'odd'"
Round towards the nearest odd digit, e.g., when rounding to nearest integer,
4.5 becomes 5, \-5.5 becomes \-5, but 5.501 becomes 6. This corresponds to the
\&\s-1IEEE 754\s0 rounding mode 'roundTiesToOdd'.
.IP "'+inf'" 4
.IX Item "'+inf'"
Round towards plus infinity, i.e., always round up. E.g., when rounding to the
nearest integer, 4.5 becomes 5, \-5.5 becomes \-5, and 4.501 also becomes 5. This
corresponds to the \s-1IEEE 754\s0 rounding mode 'roundTiesToPositive'.
.IP "'\-inf'" 4
.IX Item "'-inf'"
Round towards minus infinity, i.e., always round down. E.g., when rounding to
the nearest integer, 4.5 becomes 4, \-5.5 becomes \-6, but 4.501 becomes 5. This
corresponds to the \s-1IEEE 754\s0 rounding mode 'roundTiesToNegative'.
.IP "'zero'" 4
.IX Item "'zero'"
Round towards zero, i.e., round positive numbers down and negative numbers up.
E.g., when rounding to the nearest integer, 4.5 becomes 4, \-5.5 becomes \-5, but
4.501 becomes 5. This corresponds to the \s-1IEEE 754\s0 rounding mode
\&'roundTiesToZero'.
.IP "'common'" 4
.IX Item "'common'"
Round away from zero, i.e., round to the number with the largest absolute
value. E.g., when rounding to the nearest integer, \-1.5 becomes \-2, 1.5 becomes
2 and 1.49 becomes 1. This corresponds to the \s-1IEEE 754\s0 rounding mode
\&'roundTiesToAway'.
.PP
The handling of A & P in \s-1MBI/MBF\s0 (the old core code shipped with Perl versions
<= 5.7.2) is like this:
.IP "Precision" 4
.IX Item "Precision"
.Vb 3
\& * bfround($p) is able to round to $p number of digits after the decimal
\& point
\& * otherwise P is unused
.Ve
.IP "Accuracy (significant digits)" 4
.IX Item "Accuracy (significant digits)"
.Vb 10
\& * bround($a) rounds to $a significant digits
\& * only bdiv() and bsqrt() take A as (optional) parameter
\& + other operations simply create the same number (bneg etc), or
\& more (bmul) of digits
\& + rounding/truncating is only done when explicitly calling one
\& of bround or bfround, and never for Math::BigInt (not implemented)
\& * bsqrt() simply hands its accuracy argument over to bdiv.
\& * the documentation and the comment in the code indicate two
\& different ways on how bdiv() determines the maximum number
\& of digits it should calculate, and the actual code does yet
\& another thing
\& POD:
\& max($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(divisor) \- length(dividend);
\& So for lx = 3, ly = 9, scale = 10, scale will actually be 16 (10
\& So for lx = 3, ly = 9, scale = 10, scale will actually be 16
\& (10+9\-3). Actually, the \*(Aqdifference\*(Aq added to the scale is cal\-
\& culated from the number of "significant digits" in dividend and
\& divisor, which is derived by looking at the length of the man\-
\& tissa. Which is wrong, since it includes the + sign (oops) and
\& actually gets 2 for \*(Aq+100\*(Aq and 4 for \*(Aq+101\*(Aq. Oops again. Thus
\& 124/3 with div_scale=1 will get you \*(Aq41.3\*(Aq based on the strange
\& assumption that 124 has 3 significant digits, while 120/7 will
\& get you \*(Aq17\*(Aq, not \*(Aq17.1\*(Aq since 120 is thought to have 2 signif\-
\& icant digits. The rounding after the division then uses the
\& remainder and $y to determine whether it must round up or down.
\& ? I have no idea which is the right way. That\*(Aqs why I used a slightly more
\& ? simple scheme and tweaked the few failing testcases to match it.
.Ve
.PP
This is how it works now:
.IP "Setting/Accessing" 4
.IX Item "Setting/Accessing"
.Vb 10
\& * You can set the A global via Math::BigInt\->accuracy() or
\& Math::BigFloat\->accuracy() or whatever class you are using.
\& * You can also set P globally by using Math::SomeClass\->precision()
\& likewise.
\& * Globals are classwide, and not inherited by subclasses.
\& * to undefine A, use Math::SomeCLass\->accuracy(undef);
\& * to undefine P, use Math::SomeClass\->precision(undef);
\& * Setting Math::SomeClass\->accuracy() clears automatically
\& 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\*(Aqth 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 Math::SomeClass\->accuracy()
\& * to find out the current global P, use Math::SomeClass\->precision()
\& * use $x\->accuracy() respective $x\->precision() for the local
\& setting of $x.
\& * Please note that $x\->accuracy() respective $x\->precision()
\& return eventually defined global A or P, when $x\*(Aqs A or P is not
\& set.
.Ve
.IP "Creating numbers" 4
.IX Item "Creating numbers"
.Vb 12
\& * When you create a number, you can give the 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, NO rounding will occur, and the globals will
\& NOT be used. This is used by subclasses to create numbers without
\& suffering rounding in the parent. Thus a subclass is able to have its own
\& globals enforced upon creation of a number by using
\& $x = Math::BigInt\->new($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\*(Aqs A and P.
.Ve
.IP "Usage" 4
.IX Item "Usage"
.Vb 7
\& * 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 Math::BigInt objects 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 Math::BigFloat.
\& A flag is used to mark all Math::BigFloat numbers as \*(Aqnever round\*(Aq.
.Ve
.IP "Precedence" 4
.IX Item "Precedence"
.Vb 10
\& * 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 precedence 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 bdiv/bsqrt) and will not
\& be rounded.
\& * There is another setting for bdiv() (and thus for bsqrt()). If neither of
\& A or P is defined, bdiv() will use a fallback (F) of $div_scale digits.
\& If either the dividend\*(Aqs or the divisor\*(Aqs 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 :\-)
\& * bdiv 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 bdiv() and bsqrt() as exceptions to guard
\& against overflows. You must explicitly call bround(), bfround() or
\& round() (the latter with parameters).
\& Note: Once you have rounded a number, the settings will \*(Aqstick\*(Aq on it
\& and \*(Aqinfect\*(Aq 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()\->bround(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 \*(Aqpoison\*(Aq further math?
.Ve
.IP "Overriding globals" 4
.IX Item "Overriding globals"
.Vb 10
\& * 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
\& * bsqrt() will hand its arguments to bdiv(), as it used to, only now for two
\& arguments (A and P) instead of one
.Ve
.IP "Local settings" 4
.IX Item "Local settings"
.Vb 5
\& * You can set A or P locally by using $x\->accuracy() or
\& $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.
\& * $x\->accuracy() clears $x\->precision(), and vice versa.
.Ve
.IP "Rounding" 4
.IX Item "Rounding"
.Vb 10
\& * the rounding routines will use the respective global or local settings.
\& bround() is for accuracy rounding, while bfround() is for precision
\& * the two rounding functions take as the second parameter one of the
\& following rounding modes (R):
\& \*(Aqeven\*(Aq, \*(Aqodd\*(Aq, \*(Aq+inf\*(Aq, \*(Aq\-inf\*(Aq, \*(Aqzero\*(Aq, \*(Aqtrunc\*(Aq, \*(Aqcommon\*(Aq
\& * you can set/get the global R by using Math::SomeClass\->round_mode()
\& or by setting $Math::SomeClass::round_mode
\& * after each operation, $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 $x\->round($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 $x\->accuracy()
\& will be 4 from now on.
.Ve
.IP "Default values" 4
.IX Item "Default values"
.Vb 4
\& * R: \*(Aqeven\*(Aq
\& * F: 40
\& * A: undef
\& * P: undef
.Ve
.IP "Remarks" 4
.IX Item "Remarks"
.Vb 5
\& * The defaults are set up so that the new code gives the same results as
\& the old code (except in a few cases on bdiv):
\& + Both A and P are undefined and thus will not be used for rounding
\& after each operation.
\& + round() is thus a no\-op, unless given extra parameters A and P
.Ve
.SH "Infinity and Not a Number"
.IX Header "Infinity and Not a Number"
While Math::BigInt has extensive handling of inf and NaN, certain quirks
remain.
.IP "\fBoct()\fR/\fBhex()\fR" 4
.IX Item "oct()/hex()"
These perl routines currently (as of Perl v.5.8.6) cannot handle passed inf.
.Sp
.Vb 9
\& te@linux:~> perl \-wle \*(Aqprint 2 ** 3333\*(Aq
\& Inf
\& te@linux:~> perl \-wle \*(Aqprint 2 ** 3333 == 2 ** 3333\*(Aq
\& 1
\& te@linux:~> perl \-wle \*(Aqprint oct(2 ** 3333)\*(Aq
\& 0
\& te@linux:~> perl \-wle \*(Aqprint hex(2 ** 3333)\*(Aq
\& Illegal hexadecimal digit \*(AqI\*(Aq ignored at \-e line 1.
\& 0
.Ve
.Sp
The same problems occur if you pass them Math::BigInt\->\fBbinf()\fR objects. Since
overloading these routines is not possible, this cannot be fixed from
Math::BigInt.
.SH "INTERNALS"
.IX Header "INTERNALS"
You should neither care about nor depend on the internal representation; it
might change without notice. Use \fB\s-1ONLY\s0\fR method calls like \f(CW\*(C`$x\->sign();\*(C'\fR
instead relying on the internal representation.
.SS "\s-1MATH LIBRARY\s0"
.IX Subsection "MATH LIBRARY"
Math with the numbers is done (by default) by a module called
\&\f(CW\*(C`Math::BigInt::Calc\*(C'\fR. This is equivalent to saying:
.PP
.Vb 1
\& use Math::BigInt try => \*(AqCalc\*(Aq;
.Ve
.PP
You can change this backend library by using:
.PP
.Vb 1
\& use Math::BigInt try => \*(AqGMP\*(Aq;
.Ve
.PP
\&\fBNote\fR: General purpose packages should not be explicit about the library to
use; let the script author decide which is best.
.PP
If your script works with huge numbers and Calc is too slow for them, you can
also for the loading of one of these libraries and if none of them can be used,
the code dies:
.PP
.Vb 1
\& use Math::BigInt only => \*(AqGMP,Pari\*(Aq;
.Ve
.PP
The following would first try to find Math::BigInt::Foo, then
Math::BigInt::Bar, and when this also fails, revert to Math::BigInt::Calc:
.PP
.Vb 1
\& use Math::BigInt try => \*(AqFoo,Math::BigInt::Bar\*(Aq;
.Ve
.PP
The library that is loaded last is used. Note that this can be overwritten at
any time by loading a different library, and numbers constructed with different
libraries cannot be used in math operations together.
.PP
\fIWhat library to use?\fR
.IX Subsection "What library to use?"
.PP
\&\fBNote\fR: General purpose packages should not be explicit about the library to
use; let the script author decide which is best.
.PP
Math::BigInt::GMP and Math::BigInt::Pari are in cases involving big
numbers much faster than Calc, however it is slower when dealing with very
small numbers (less than about 20 digits) and when converting very large
numbers to decimal (for instance for printing, rounding, calculating their
length in decimal etc).
.PP
So please select carefully what library you want to use.
.PP
Different low-level libraries use different formats to store the numbers.
However, you should \fB\s-1NOT\s0\fR depend on the number having a specific format
internally.
.PP
See the respective math library module documentation for further details.
.SS "\s-1SIGN\s0"
.IX Subsection "SIGN"
The sign is either '+', '\-', 'NaN', '+inf' or '\-inf'.
.PP
A sign of 'NaN' is used to represent the result when input arguments are not
numbers or as a result of 0/0. '+inf' and '\-inf' represent plus respectively
minus infinity. You get '+inf' when dividing a positive number by 0, and '\-inf'
when dividing any negative number by 0.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
.Vb 1
\& use Math::BigInt;
\&
\& sub bigint { Math::BigInt\->new(shift); }
\&
\& $x = Math::BigInt\->bstr("1234") # string "1234"
\& $x = "$x"; # same as bstr()
\& $x = Math::BigInt\->bneg("1234"); # Math::BigInt "\-1234"
\& $x = Math::BigInt\->babs("\-12345"); # Math::BigInt "12345"
\& $x = Math::BigInt\->bnorm("\-0.00"); # Math::BigInt "0"
\& $x = bigint(1) + bigint(2); # Math::BigInt "3"
\& $x = bigint(1) + "2"; # ditto (auto\-Math::BigIntify of "2")
\& $x = bigint(1); # Math::BigInt "1"
\& $x = $x + 5 / 2; # Math::BigInt "3"
\& $x = $x ** 3; # Math::BigInt "27"
\& $x *= 2; # Math::BigInt "54"
\& $x = Math::BigInt\->new(0); # Math::BigInt "0"
\& $x\-\-; # Math::BigInt "\-1"
\& $x = Math::BigInt\->badd(4,5) # Math::BigInt "9"
\& print $x\->bsstr(); # 9e+0
.Ve
.PP
Examples for rounding:
.PP
.Vb 2
\& use Math::BigFloat;
\& use Test::More;
\&
\& $x = Math::BigFloat\->new(123.4567);
\& $y = Math::BigFloat\->new(123.456789);
\& Math::BigFloat\->accuracy(4); # no more A than 4
\&
\& is ($x\->copy()\->bround(),123.4); # even rounding
\& print $x\->copy()\->bround(),"\en"; # 123.4
\& Math::BigFloat\->round_mode(\*(Aqodd\*(Aq); # round to odd
\& print $x\->copy()\->bround(),"\en"; # 123.5
\& Math::BigFloat\->accuracy(5); # no more A than 5
\& Math::BigFloat\->round_mode(\*(Aqodd\*(Aq); # round to odd
\& print $x\->copy()\->bround(),"\en"; # 123.46
\& $y = $x\->copy()\->bround(4),"\en"; # A = 4: 123.4
\& print "$y, ",$y\->accuracy(),"\en"; # 123.4, 4
\&
\& Math::BigFloat\->accuracy(undef); # A not important now
\& Math::BigFloat\->precision(2); # P important
\& print $x\->copy()\->bnorm(),"\en"; # 123.46
\& print $x\->copy()\->bround(),"\en"; # 123.46
.Ve
.PP
Examples for converting:
.PP
.Vb 2
\& my $x = Math::BigInt\->new(\*(Aq0b1\*(Aq.\*(Aq01\*(Aq x 123);
\& print "bin: ",$x\->as_bin()," hex:",$x\->as_hex()," dec: ",$x,"\en";
.Ve
.SH "Autocreating constants"
.IX Header "Autocreating constants"
After \f(CW\*(C`use Math::BigInt \*(Aq:constant\*(Aq\*(C'\fR all the \fBinteger\fR decimal, hexadecimal
and binary constants in the given scope are converted to \f(CW\*(C`Math::BigInt\*(C'\fR. This
conversion happens at compile time.
.PP
In particular,
.PP
.Vb 1
\& perl \-MMath::BigInt=:constant \-e \*(Aqprint 2**100,"\en"\*(Aq
.Ve
.PP
prints the integer value of \f(CW\*(C`2**100\*(C'\fR. Note that without conversion of
constants the expression 2**100 is calculated using Perl scalars.
.PP
Please note that strings and floating point constants are not affected, so that
.PP
.Vb 1
\& use Math::BigInt qw/:constant/;
\&
\& $x = 1234567890123456789012345678901234567890
\& + 123456789123456789;
\& $y = \*(Aq1234567890123456789012345678901234567890\*(Aq
\& + \*(Aq123456789123456789\*(Aq;
.Ve
.PP
does not give you what you expect. You need an explicit Math::BigInt\->\fBnew()\fR
around one of the operands. You should also quote large constants to protect
loss of precision:
.PP
.Vb 1
\& use Math::BigInt;
\&
\& $x = Math::BigInt\->new(\*(Aq1234567889123456789123456789123456789\*(Aq);
.Ve
.PP
Without the quotes Perl would convert the large number to a floating point
constant at compile time and then hand the result to Math::BigInt, which
results in an truncated result or a NaN.
.PP
This also applies to integers that look like floating point constants:
.PP
.Vb 1
\& use Math::BigInt \*(Aq:constant\*(Aq;
\&
\& print ref(123e2),"\en";
\& print ref(123.2e2),"\en";
.Ve
.PP
prints nothing but newlines. Use either bignum or Math::BigFloat to get
this to work.
.SH "PERFORMANCE"
.IX Header "PERFORMANCE"
Using the form \f(CW$x\fR += \f(CW$y\fR; etc over \f(CW$x\fR = \f(CW$x\fR + \f(CW$y\fR is faster, since a copy of \f(CW$x\fR
must be made in the second case. For long numbers, the copy can eat up to 20%
of the work (in the case of addition/subtraction, less for
multiplication/division). If \f(CW$y\fR is very small compared to \f(CW$x\fR, the form \f(CW$x\fR += \f(CW$y\fR
is \s-1MUCH\s0 faster than \f(CW$x\fR = \f(CW$x\fR + \f(CW$y\fR since making the copy of \f(CW$x\fR takes more time
then the actual addition.
.PP
With a technique called copy-on-write, the cost of copying with overload could
be minimized or even completely avoided. A test implementation of \s-1COW\s0 did show
performance gains for overloaded math, but introduced a performance loss due to
a constant overhead for all other operations. So Math::BigInt does currently
not \s-1COW.\s0
.PP
The rewritten version of this module (vs. v0.01) is slower on certain
operations, like \f(CW\*(C`new()\*(C'\fR, \f(CW\*(C`bstr()\*(C'\fR and \f(CW\*(C`numify()\*(C'\fR. The reason are that it
does now more work and handles much more cases. The time spent in these
operations 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.
.PP
Some operations may be slower for small numbers, but are significantly faster
for big numbers. Other operations are now constant (O(1), like \f(CW\*(C`bneg()\*(C'\fR,
\&\f(CW\*(C`babs()\*(C'\fR etc), instead of O(N) and thus nearly always take much less time.
These optimizations were done on purpose.
.PP
If you find the Calc module to slow, try to install any of the replacement
modules and see if they help you.
.SS "Alternative math libraries"
.IX Subsection "Alternative math libraries"
You can use an alternative library to drive Math::BigInt. See the section
\&\*(L"\s-1MATH LIBRARY\*(R"\s0 for more information.
.PP
For more benchmark results see <http://bloodgate.com/perl/benchmarks.html>.
.SH "SUBCLASSING"
.IX Header "SUBCLASSING"
.SS "Subclassing Math::BigInt"
.IX Subsection "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:
.IP "\(bu" 4
The public \s-1API\s0 must remain consistent, i.e. if a sub-class is overloading
addition, the sub-class must use the same name, in this case \fBbadd()\fR. The reason
for this is that Math::BigInt is optimized to call the object methods directly.
.IP "\(bu" 4
The private object hash keys like \f(CW\*(C`$x\->{sign}\*(C'\fR may not be changed, but
additional keys can be added, like \f(CW\*(C`$x\->{_custom}\*(C'\fR.
.IP "\(bu" 4
Accessor functions are available for all existing object hash keys and should
be used instead of directly accessing the internal hash keys. The reason for
this is that Math::BigInt itself has a pluggable interface which permits it to
support different storage methods.
.PP
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 \f(CW\*(C`bstr()\*(C'\fR.
.PP
All other object methods and overloaded functions can be directly inherited
from the parent class.
.PP
At the very minimum, any subclass needs to provide its own \f(CW\*(C`new()\*(C'\fR and can
store additional hash keys in the object. There are also some package globals
that must be defined, e.g.:
.PP
.Vb 5
\& # Globals
\& $accuracy = undef;
\& $precision = \-2; # round to 2 decimal places
\& $round_mode = \*(Aqeven\*(Aq;
\& $div_scale = 40;
.Ve
.PP
Additionally, you might want to provide the following two globals to allow
auto-upgrading and auto-downgrading to work correctly:
.PP
.Vb 2
\& $upgrade = undef;
\& $downgrade = undef;
.Ve
.PP
This allows Math::BigInt to correctly retrieve package globals from the
subclass, like \f(CW$SubClass::precision\fR. See t/Math/BigInt/Subclass.pm or
t/Math/BigFloat/SubClass.pm completely functional subclass examples.
.PP
Don't forget to
.PP
.Vb 1
\& use overload;
.Ve
.PP
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.
.SH "UPGRADING"
.IX Header "UPGRADING"
When used like this:
.PP
.Vb 1
\& use Math::BigInt upgrade => \*(AqFoo::Bar\*(Aq;
.Ve
.PP
certain operations 'upgrade' their calculation and thus the result to the class
Foo::Bar. Usually this is used in conjunction with Math::BigFloat:
.PP
.Vb 1
\& use Math::BigInt upgrade => \*(AqMath::BigFloat\*(Aq;
.Ve
.PP
As a shortcut, you can use the module bignum:
.PP
.Vb 1
\& use bignum;
.Ve
.PP
Also good for one-liners:
.PP
.Vb 1
\& perl \-Mbignum \-le \*(Aqprint 2 ** 255\*(Aq
.Ve
.PP
This makes it possible to mix arguments of different classes (as in 2.5 + 2) as
well es preserve accuracy (as in \fBsqrt\fR\|(3)).
.PP
Beware: This feature is not fully implemented yet.
.SS "Auto-upgrade"
.IX Subsection "Auto-upgrade"
The following methods upgrade themselves unconditionally; that is if upgrade is
in effect, they always hands up their work:
.PP
.Vb 1
\& div bsqrt blog bexp bpi bsin bcos batan batan2
.Ve
.PP
All other methods upgrade themselves only when one (or all) of their arguments
are of the class mentioned in \f(CW$upgrade\fR.
.SH "EXPORTS"
.IX Header "EXPORTS"
\&\f(CW\*(C`Math::BigInt\*(C'\fR exports nothing by default, but can export the following
methods:
.PP
.Vb 2
\& bgcd
\& blcm
.Ve
.SH "CAVEATS"
.IX Header "CAVEATS"
Some things might not work as you expect them. Below is documented what is
known to be troublesome:
.IP "Comparing numbers as strings" 4
.IX Item "Comparing numbers as strings"
Both \f(CW\*(C`bstr()\*(C'\fR and \f(CW\*(C`bsstr()\*(C'\fR as well as stringify via overload drop the
leading '+'. This is to be consistent with Perl and to make \f(CW\*(C`cmp\*(C'\fR (especially
with overloading) to work as you expect. It also solves problems with
\&\f(CW\*(C`Test.pm\*(C'\fR and Test::More, which stringify arguments before comparing them.
.Sp
Mark Biggar said, when asked about to drop the '+' altogether, or make only
\&\f(CW\*(C`cmp\*(C'\fR work:
.Sp
.Vb 4
\& I agree (with the first alternative), don\*(Aqt add the \*(Aq+\*(Aq on positive
\& numbers. It\*(Aqs 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.
.Ve
.Sp
So, the following examples now works as expected:
.Sp
.Vb 2
\& use Test::More tests => 1;
\& use Math::BigInt;
\&
\& my $x = Math::BigInt \-> new(3*3);
\& my $y = Math::BigInt \-> new(3*3);
\&
\& is($x,3*3, \*(Aqmultiplication\*(Aq);
\& print "$x eq 9" if $x eq $y;
\& print "$x eq 9" if $x eq \*(Aq9\*(Aq;
\& print "$x eq 9" if $x eq 3*3;
.Ve
.Sp
Additionally, the following still works:
.Sp
.Vb 3
\& print "$x == 9" if $x == $y;
\& print "$x == 9" if $x == 9;
\& print "$x == 9" if $x == 3*3;
.Ve
.Sp
There is now a \f(CW\*(C`bsstr()\*(C'\fR method to get the string in scientific notation aka
\&\f(CW1e+2\fR instead of \f(CW100\fR. Be advised that overloaded 'eq' always uses \fBbstr()\fR
for comparison, but Perl represents some numbers as 100 and others as 1e+308.
If in doubt, convert both arguments to Math::BigInt before comparing them as
strings:
.Sp
.Vb 2
\& use Test::More tests => 3;
\& use Math::BigInt;
\&
\& $x = Math::BigInt\->new(\*(Aq1e56\*(Aq); $y = 1e56;
\& is($x,$y); # fails
\& is($x\->bsstr(),$y); # okay
\& $y = Math::BigInt\->new($y);
\& is($x,$y); # okay
.Ve
.Sp
Alternatively, simply use \f(CW\*(C`<=>\*(C'\fR for comparisons, this always gets it
right. There is not yet a way to get a number automatically represented as a
string that matches exactly the way Perl represents it.
.Sp
See also the section about \*(L"Infinity and Not a Number\*(R" for problems in
comparing NaNs.
.IP "\fBint()\fR" 4
.IX Item "int()"
\&\f(CW\*(C`int()\*(C'\fR returns (at least for Perl v5.7.1 and up) another Math::BigInt, not a
Perl scalar:
.Sp
.Vb 4
\& $x = Math::BigInt\->new(123);
\& $y = int($x); # 123 as a Math::BigInt
\& $x = Math::BigFloat\->new(123.45);
\& $y = int($x); # 123 as a Math::BigFloat
.Ve
.Sp
If you want a real Perl scalar, use \f(CW\*(C`numify()\*(C'\fR:
.Sp
.Vb 1
\& $y = $x\->numify(); # 123 as a scalar
.Ve
.Sp
This is seldom necessary, though, because this is done automatically, like when
you access an array:
.Sp
.Vb 1
\& $z = $array[$x]; # does work automatically
.Ve
.IP "Modifying and =" 4
.IX Item "Modifying and ="
Beware of:
.Sp
.Vb 2
\& $x = Math::BigFloat\->new(5);
\& $y = $x;
.Ve
.Sp
This makes a second reference to the \fBsame\fR object and stores it in \f(CW$y\fR. Thus
anything that modifies \f(CW$x\fR (except overloaded operators) also modifies \f(CW$y\fR, and
vice versa. Or in other words, \f(CW\*(C`=\*(C'\fR is only safe if you modify your
Math::BigInt objects only via overloaded math. As soon as you use a method call
it breaks:
.Sp
.Vb 2
\& $x\->bmul(2);
\& print "$x, $y\en"; # prints \*(Aq10, 10\*(Aq
.Ve
.Sp
If you want a true copy of \f(CW$x\fR, use:
.Sp
.Vb 1
\& $y = $x\->copy();
.Ve
.Sp
You can also chain the calls like this, this first makes a copy and then
multiply it by 2:
.Sp
.Vb 1
\& $y = $x\->copy()\->bmul(2);
.Ve
.Sp
See also the documentation for overload.pm regarding \f(CW\*(C`=\*(C'\fR.
.IP "Overloading \-$x" 4
.IX Item "Overloading -$x"
The following:
.Sp
.Vb 1
\& $x = \-$x;
.Ve
.Sp
is slower than
.Sp
.Vb 1
\& $x\->bneg();
.Ve
.Sp
since overload calls \f(CW\*(C`sub($x,0,1);\*(C'\fR instead of \f(CW\*(C`neg($x)\*(C'\fR. The first variant
needs to preserve \f(CW$x\fR since it does not know that it later gets overwritten.
This makes a copy of \f(CW$x\fR and takes O(N), but \f(CW$x\fR\->\fBbneg()\fR is O(1).
.IP "Mixing different object types" 4
.IX Item "Mixing different object types"
With overloaded operators, it is the first (dominating) operand that determines
which method is called. Here are some examples showing what actually gets
called in various cases.
.Sp
.Vb 2
\& use Math::BigInt;
\& use Math::BigFloat;
\&
\& $mbf = Math::BigFloat\->new(5);
\& $mbi2 = Math::BigInt\->new(5);
\& $mbi = Math::BigInt\->new(2);
\& # what actually gets called:
\& $float = $mbf + $mbi; # $mbf\->badd($mbi)
\& $float = $mbf / $mbi; # $mbf\->bdiv($mbi)
\& $integer = $mbi + $mbf; # $mbi\->badd($mbf)
\& $integer = $mbi2 / $mbi; # $mbi2\->bdiv($mbi)
\& $integer = $mbi2 / $mbf; # $mbi2\->bdiv($mbf)
.Ve
.Sp
For instance, Math::BigInt\->\fBbdiv()\fR always returns a Math::BigInt, regardless of
whether the second operant is a Math::BigFloat. To get a Math::BigFloat you
either need to call the operation manually, make sure each operand already is a
Math::BigFloat, or cast to that type via Math::BigFloat\->\fBnew()\fR:
.Sp
.Vb 1
\& $float = Math::BigFloat\->new($mbi2) / $mbi; # = 2.5
.Ve
.Sp
Beware of casting the entire expression, as this would cast the
result, at which point it is too late:
.Sp
.Vb 1
\& $float = Math::BigFloat\->new($mbi2 / $mbi); # = 2
.Ve
.Sp
Beware also of the order of more complicated expressions like:
.Sp
.Vb 2
\& $integer = ($mbi2 + $mbi) / $mbf; # int / float => int
\& $integer = $mbi2 / Math::BigFloat\->new($mbi); # ditto
.Ve
.Sp
If in doubt, break the expression into simpler terms, or cast all operands
to the desired resulting type.
.Sp
Scalar values are a bit different, since:
.Sp
.Vb 2
\& $float = 2 + $mbf;
\& $float = $mbf + 2;
.Ve
.Sp
both result in the proper type due to the way the overloaded math works.
.Sp
This section also applies to other overloaded math packages, like Math::String.
.Sp
One solution to you problem might be autoupgrading|upgrading. See the
pragmas bignum, bigint and bigrat for an easy way to do this.
.SH "BUGS"
.IX Header "BUGS"
Please report any bugs or feature requests to
\&\f(CW\*(C`bug\-math\-bigint at rt.cpan.org\*(C'\fR, or through the web interface at
<https://rt.cpan.org/Ticket/Create.html?Queue=Math\-BigInt> (requires login).
We will be notified, and then you'll automatically be notified of progress on
your bug as I make changes.
.SH "SUPPORT"
.IX Header "SUPPORT"
You can find documentation for this module with the perldoc command.
.PP
.Vb 1
\& perldoc Math::BigInt
.Ve
.PP
You can also look for information at:
.IP "\(bu" 4
\&\s-1RT: CPAN\s0's request tracker
.Sp
<https://rt.cpan.org/Public/Dist/Display.html?Name=Math\-BigInt>
.IP "\(bu" 4
AnnoCPAN: Annotated \s-1CPAN\s0 documentation
.Sp
<http://annocpan.org/dist/Math\-BigInt>
.IP "\(bu" 4
\&\s-1CPAN\s0 Ratings
.Sp
<http://cpanratings.perl.org/dist/Math\-BigInt>
.IP "\(bu" 4
Search \s-1CPAN\s0
.Sp
<http://search.cpan.org/dist/Math\-BigInt/>
.IP "\(bu" 4
\&\s-1CPAN\s0 Testers Matrix
.Sp
<http://matrix.cpantesters.org/?dist=Math\-BigInt>
.IP "\(bu" 4
The Bignum mailing list
.RS 4
.IP "\(bu" 4
Post to mailing list
.Sp
\&\f(CW\*(C`bignum at lists.scsys.co.uk\*(C'\fR
.IP "\(bu" 4
View mailing list
.Sp
<http://lists.scsys.co.uk/pipermail/bignum/>
.IP "\(bu" 4
Subscribe/Unsubscribe
.Sp
<http://lists.scsys.co.uk/cgi\-bin/mailman/listinfo/bignum>
.RE
.RS 4
.RE
.SH "LICENSE"
.IX Header "LICENSE"
This program is free software; you may redistribute it and/or modify it under
the same terms as Perl itself.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Math::BigFloat and Math::BigRat as well as the backends
Math::BigInt::FastCalc, Math::BigInt::GMP, and Math::BigInt::Pari.
.PP
The pragmas bignum, bigint and bigrat also might be of interest
because they solve the autoupgrading/downgrading issue, at least partly.
.SH "AUTHORS"
.IX Header "AUTHORS"
.IP "\(bu" 4
Mark Biggar, overloaded interface by Ilya Zakharevich, 1996\-2001.
.IP "\(bu" 4
Completely rewritten by Tels <http://bloodgate.com>, 2001\-2008.
.IP "\(bu" 4
Florian Ragwitz <flora@cpan.org>, 2010.
.IP "\(bu" 4
Peter John Acklam <pjacklam@online.no>, 2011\-.
.PP
Many people contributed in one or more ways to the final beast, see the file
\&\s-1CREDITS\s0 for an (incomplete) list. If you miss your name, please drop me a
mail. Thank you!