Scroll to navigation

Math::BigRat(3perl) Perl Programmers Reference Guide Math::BigRat(3perl)

NAME

Math::BigRat - arbitrary size rational number math package

SYNOPSIS

    use Math::BigRat;
    my $x = Math::BigRat->new('3/7'); $x += '5/9';
    print $x->bstr(), "\n";
    print $x ** 2, "\n";
    my $y = Math::BigRat->new('inf');
    print "$y ", ($y->is_inf ? 'is' : 'is not'), " infinity\n";
    my $z = Math::BigRat->new(144); $z->bsqrt();

DESCRIPTION

Math::BigRat complements Math::BigInt and Math::BigFloat by providing support for arbitrary big rational numbers.

MATH LIBRARY

You can change the underlying module that does the low-level math operations by using:

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

Note: This needs Math::BigInt::GMP installed.

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::BigRat try => 'Foo,Math::BigInt::Bar';

If you want to get warned when the fallback occurs, replace "try" with "lib":

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

If you want the code to die instead, replace "try" with "only":

    use Math::BigRat only => 'Foo,Math::BigInt::Bar';

METHODS

Any methods not listed here are derived from Math::BigFloat (or Math::BigInt), so make sure you check these two modules for further information.

    $x = Math::BigRat->new('1/3');

Create a new Math::BigRat object. Input can come in various forms:

    $x = Math::BigRat->new(123);                            # scalars
    $x = Math::BigRat->new('inf');                          # infinity
    $x = Math::BigRat->new('123.3');                        # float
    $x = Math::BigRat->new('1/3');                          # simple string
    $x = Math::BigRat->new('1 / 3');                        # spaced
    $x = Math::BigRat->new('1 / 0.1');                      # w/ floats
    $x = Math::BigRat->new(Math::BigInt->new(3));           # BigInt
    $x = Math::BigRat->new(Math::BigFloat->new('3.1'));     # BigFloat
    $x = Math::BigRat->new(Math::BigInt::Lite->new('2'));   # BigLite
    # You can also give D and N as different objects:
    $x = Math::BigRat->new(
            Math::BigInt->new(-123),
            Math::BigInt->new(7),
         );                      # => -123/7
    
    $n = $x->numerator();

Returns a copy of the numerator (the part above the line) as signed BigInt.

    $d = $x->denominator();

Returns a copy of the denominator (the part under the line) as positive BigInt.

    ($n, $d) = $x->parts();

Return a list consisting of (signed) numerator and (unsigned) denominator as BigInts.

Returns the integer part and the fraction part.
Returns the smallest possible numerator and denominator so that the numerator divided by the denominator gives back the original value. For finite numbers, both values are integers. Mnemonic: fraction.
    my $y = $x->numify();

Returns the object as a scalar. This will lose some data if the object cannot be represented by a normal Perl scalar (integer or float), so use "as_int()" or "as_float()" instead.

This routine is automatically used whenever a scalar is required:

    my $x = Math::BigRat->new('3/1');
    @array = (0, 1, 2, 3);
    $y = $array[$x];                # set $y to 3
    
    $x = Math::BigRat->new('13/7');
    print $x->as_int(), "\n";               # '1'

Returns a copy of the object as BigInt, truncated to an integer.

as_number() is an alias for as_int().

    $x = Math::BigRat->new('13/7');
    print $x->as_float(), "\n";             # '1'
    $x = Math::BigRat->new('2/3');
    print $x->as_float(5), "\n";            # '0.66667'

Returns a copy of the object as BigFloat, preserving the accuracy as wanted, or the default of 40 digits.

This method was added in v0.22 of Math::BigRat (April 2008).

    $x = Math::BigRat->new('13');
    print $x->as_hex(), "\n";               # '0xd'

Returns the BigRat as hexadecimal string. Works only for integers.

    $x = Math::BigRat->new('13');
    print $x->as_bin(), "\n";               # '0x1101'

Returns the BigRat as binary string. Works only for integers.

    $x = Math::BigRat->new('13');
    print $x->as_oct(), "\n";               # '015'

Returns the BigRat as octal string. Works only for integers.

    my $h = Math::BigRat->from_hex('0x10');

Create a BigRat from a hexadecimal number in string form.

    my $o = Math::BigRat->from_oct('020');

Create a BigRat from an octal number in string form.

    my $b = Math::BigRat->from_bin('0b10000000');

Create a BigRat from an binary number in string form.

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

Creates a new BigRat object representing NaN (Not A Number). If used on an object, it will set it to NaN:

    $x->bnan();
    
    $x = Math::BigRat->bzero();

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

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

Creates a new BigRat 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('-');
    
    $x = Math::BigRat->bone($sign);

Creates a new BigRat 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
    
    $len = $x->length();

Return the length of $x in digits for integer values.

    print Math::BigRat->new('123/1')->digit(1);     # 1
    print Math::BigRat->new('123/1')->digit(-1);    # 3

Return the N'ths digit from X when X is an integer value.

    $x->bnorm();

Reduce the number to the shortest form. This routine is called automatically whenever it is needed.

    $x->bfac();

Calculates the factorial of $x. For instance:

    print Math::BigRat->new('3/1')->bfac(), "\n";   # 1*2*3
    print Math::BigRat->new('5/1')->bfac(), "\n";   # 1*2*3*4*5

Works currently only for integers.

Are not yet implemented.
    $x->bmod($y);

Returns $x modulo $y. When $x is finite, and $y is finite and non-zero, the result is identical to the remainder after floored division (F-division). If, in addition, both $x and $y are integers, the result is identical to the result from Perl's % operator.

    $x->bmodinv($mod);          # modular multiplicative inverse

Returns the multiplicative inverse of $x modulo $mod. If

    $y = $x -> copy() -> bmodinv($mod)

then $y is the number closest to zero, and with the same sign as $mod, satisfying

    ($x * $y) % $mod = 1 % $mod

If $x and $y are non-zero, they must be relative primes, i.e., "bgcd($y, $mod)==1". '"NaN"' is returned when no modular multiplicative inverse exists.

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

Returns the value of $num taken to the power $exp in the modulus $mod using binary exponentiation. "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)
    
    $x->bneg();

Used to negate the object in-place.

    print "$x is 1\n" if $x->is_one();

Return true if $x is exactly one, otherwise false.

    print "$x is 0\n" if $x->is_zero();

Return true if $x is exactly zero, otherwise false.

    print "$x is >= 0\n" if $x->is_positive();

Return true if $x is positive (greater than or equal to zero), otherwise false. Please note that '+inf' is also positive, while 'NaN' and '-inf' aren't.

is_positive() is an alias for is_pos().

    print "$x is < 0\n" if $x->is_negative();

Return true if $x is negative (smaller than zero), otherwise false. Please note that '-inf' is also negative, while 'NaN' and '+inf' aren't.

is_negative() is an alias for is_neg().

    print "$x is an integer\n" if $x->is_int();

Return true if $x has a denominator of 1 (e.g. no fraction parts), otherwise false. Please note that '-inf', 'inf' and 'NaN' aren't integer.

    print "$x is odd\n" if $x->is_odd();

Return true if $x is odd, otherwise false.

    print "$x is even\n" if $x->is_even();

Return true if $x is even, otherwise false.

    $x->bceil();

Set $x to the next bigger integer value (e.g. truncate the number to integer and then increment it by one).

    $x->bfloor();

Truncate $x to an integer value.

    $x->bint();

Round $x towards zero.

    $x->bsqrt();

Calculate the square root of $x.

    $x->broot($n);

Calculate the N'th root of $x.

    $x->badd($y);

Adds $y to $x and returns the result.

    $x->bmul($y);

Multiplies $y to $x and returns the result.

    $x->bsub($y);

Subtracts $y from $x and returns the result.

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

In scalar context, divides $x by $y and returns the result. In list context, does floored division (F-division), returning an integer $q and a remainder $r so that $x = $q * $y + $r. The remainer (modulo) is equal to what is returned by "$x->bmod($y)".

    $x->binv();

Inverse of $x.

    $x->bdec();

Decrements $x by 1 and returns the result.

    $x->binc();

Increments $x by 1 and returns the result.

    my $z = $x->copy();

Makes a deep copy of the object.

Please see the documentation in Math::BigInt for further details.

    my $x = Math::BigRat->new('8/4');
    print $x->bstr(), "\n";             # prints 1/2
    print $x->bsstr(), "\n";            # prints 1/2

Return a string representing this object.

    $x->bcmp($y);

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

    $x->bacmp($y);

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

    $x -> beq($y);

Returns true if and only if $x is equal to $y, and false otherwise.

    $x -> bne($y);

Returns true if and only if $x is not equal to $y, and false otherwise.

    $x -> blt($y);

Returns true if and only if $x is equal to $y, and false otherwise.

    $x -> ble($y);

Returns true if and only if $x is less than or equal to $y, and false otherwise.

    $x -> bgt($y);

Returns true if and only if $x is greater than $y, and false otherwise.

    $x -> bge($y);

Returns true if and only if $x is greater than or equal to $y, and false otherwise.

Used to shift numbers left/right.

Please see the documentation in Math::BigInt for further details.

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

Compute $x ** $y.

Please see the documentation in Math::BigInt for further details.

    $x->blog($base, $accuracy);         # logarithm of x to the base $base

If $base is not defined, Euler's number (e) is used:

    print $x->blog(undef, 100);         # log(x) to 100 digits
    
    $x->bexp($accuracy);        # calculate e ** X

Calculates two integers A and B so that A/B is equal to "e ** $x", where "e" is Euler's number.

This method was added in v0.20 of Math::BigRat (May 2007).

See also blog().

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

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

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

This method was added in v0.20 of Math::BigRat (May 2007).

    Math::BigRat->config("trap_nan" => 1);      # set
    $accu = Math::BigRat->config("accuracy");   # get

Set or get configuration parameter values. Read-only parameters are marked as RO. Read-write parameters are marked as RW. The following parameters are supported.

    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 div, sqrt etc.
                            40
    trap_nan        RW      Trap NaNs
                            undef
    trap_inf        RW      Trap +inf/-inf
                            undef

NUMERIC LITERALS

After "use Math::BigRat ':constant'" all numeric literals in the given scope are converted to "Math::BigRat" objects. This conversion happens at compile time. Every non-integer is convert to a NaN.

For example,

    perl -MMath::BigRat=:constant -le 'print 2**150'

prints the exact value of "2**150". Note that without conversion of constants to objects the expression "2**150" is calculated using Perl scalars, which leads to an inaccurate result.

Please note that strings are not affected, so that

    use Math::BigRat qw/:constant/;
    $x = "1234567890123456789012345678901234567890"
            + "123456789123456789";

does give you what you expect. You need an explicit Math::BigRat->new() around at least one of the operands. You should also quote large constants to prevent loss of precision:

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

Without the quotes Perl first converts the large number to a floating point constant at compile time, and then converts the result to a Math::BigRat object at run time, which results in an inaccurate result.

Hexadecimal, octal, and binary floating point literals

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

Hexadecimal floating point literals:

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

Octal floating point literals (with "0" prefix):

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

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

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

Binary floating point literals:

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

BUGS

Please report any bugs or feature requests to "bug-math-bigint at rt.cpan.org", or through the web interface at <https://rt.cpan.org/Ticket/Create.html?Queue=Math-BigInt> (requires login). We will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc Math::BigInt

You can also look for information at:

LICENSE

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

SEE ALSO

Math::BigInt and Math::BigFloat as well as the backend libraries Math::BigInt::FastCalc, Math::BigInt::GMP, and Math::BigInt::Pari, Math::BigInt::GMPz, and Math::BigInt::BitVect.

The pragmas bigint, bigfloat, and bigrat might also be of interest. In addition there is the bignum pragma which does upgrading and downgrading.

AUTHORS

2024-09-13 perl v5.40.0