role Real

Non-complex number

role Real does Numeric { ... }

Common role for non-Complex numbers.


method Bridge

Defined as:

method Bridge(Real:D:)

Default implementation coerces the invocant to Num and that's the behaviour of this method in core Real types. This method primarily exist to make it easy to implement custom Real types by users, with the Bridge method returning one of the core Real types (NOT necessarily a Num) that best represent the custom Real type. In turn, this lets all the core operators and methods obtain a usable value they can work with.

As an example, we can implement a custom Temperature type. It has a unit of measure and the value, which are given during instantiation. We can implement custom operators or conversion methods that work with this type. When it comes to regular mathematical operators, however, we can simply use the .Bridge method to convert the Temperature to Kelvin expressed in one of the core numeric types:

class Temperature is Real {
    has Str:D  $.unit  is required where any <K F C>;
    has Real:D $.value is required;
    method new ($value:$unit = 'K'{ self.bless :$value :$unit }
    # Note: implementing .new() that handles $value of type Temperature is left as an exercise 
    method Bridge {
        when $!unit eq 'F' { ($!value + 459.67) × 9/5 }
        when $!unit eq 'C' {  $!value + 273.15 }
    method gist { self.Str }
    method Str  { "$!value degrees $!unit" }
sub postfix:<> { $^value:unit<C> }
sub postfix:<> { $^value:unit<F> }
sub postfix:<K> { $^value:unit<K> }
my $human := 36.6℃;
my $book  := 451℉;
my $sun   := 5778K;
say $human;                # OUTPUT: «36.6 degrees C␤» 
say $human + $book + $sun# OUTPUT: «7726.956␤» 
say 123+ 456K;           # OUTPUT: «579␤» 

As we can see from the last two lines of the output, the type of the bridged result is not forced to be any particular core type. It is a Rat, when we instantiated Temperature with a Rat or when conversion was involved, and it is an Int when we instantiated Temperature with an Int.

method Complex

method Complex(Real:D: --> Complex:D)

Converts the number to a Complex with the number converted to a Num as its real part and 0e0 as the imaginary part.

method Rat

method Rat(Real:D: Real $epsilon = 1e-6)

Converts the number to a Rat with the precision $epsilon.

method Real

Defined as:

multi method Real(Real:D: --> Real:D)
multi method Real(Real:U: --> Real:D)

The :D variant simply returns the invocant. The :U variant issues a warning about using an uninitialized value in numeric context and then returns

routine rand

sub term:<rand> (--> Num:D)
method rand(Real:D: --> Real:D)

Returns a pseudo-random number between zero (inclusive) and the number (non-inclusive). The Bridge method is used to coerce the Real to a numeric that supports rand method.

The term form returns a pseudo-random Num between 0e0 (inclusive) and 1e0 (non-inclusive.)

method sign

method sign(Real:D:)

Returns -1 if the number is negative, 0 if it is zero and 1 otherwise.

method round

method round(Real:D: $scale = 1)

Rounds the number to scale $scale. If $scale is 1, rounds to an integer. If scale is 0.1, rounds to one digit after the comma etc.

method floor

method floor(Real:D --> Int:D)

Return the largest integer not greater than the number.

method ceiling

method ceiling(Real:D --> Int:D)

Returns the smallest integer not less than the number.

method truncate

method truncate(Real:D --> Int:D)

Rounds the number towards zero.

method base

method base(Real:D: Int:D $base where 2..36$digits? --> Str:D)

Converts the number to a string, using $base as base. For $base larger than ten, capital Latin letters are used.

255.base(16);            # 'FF' 

The optional $digits argument asks for that many digits of fraction (which may not be negative). If omitted, a reasonable default is chosen based on type. For Int this default is 0. For Num, the default is 8. For Rational, the number of places is scaled to the size of the denominator, with a minimum of 6.

A special value of Whatever (*) can be given as $digits, which functions the same as when $digits is not specified for all Real types except the Rationals. For Rationals, the Whatever indicates that you wish all of the possible digits of the fractional part, but use caution: since there's no detection of repeating fractional parts (the algorithm will eventually stop after generating 2**63 digits).

The final digit produced is always rounded.

say pi.base(103);      # OUTPUT: «3.142␤» 
say (1/128).base(10*); # OUTPUT: «0.0078125␤» 
say (1/100).base(10*); # OUTPUT: «0.01␤» 
say (1/3)  .base(10*); # WRONG: endlessly repeating fractional part 

For reverse operation, see parse-base

Type Graph

Type relations for Real
perl6-type-graph Real Real Numeric Numeric Real->Numeric Rational Rational Rational->Real Mu Mu Any Any Any->Mu Cool Cool Cool->Any Instant Instant Instant->Real Instant->Cool Int Int Int->Real Int->Cool Duration Duration Duration->Real Duration->Cool Num Num Num->Real Num->Cool PromiseStatus PromiseStatus PromiseStatus->Int atomicint atomicint atomicint->Int Bool Bool Bool->Int Stringy Stringy Str Str Str->Cool Str->Stringy IntStr IntStr IntStr->Int IntStr->Str Signal Signal Signal->Int Order Order Order->Int int int int->Int NumStr NumStr NumStr->Num NumStr->Str Rat Rat Rat->Rational Rat->Cool FatRat FatRat FatRat->Rational FatRat->Cool

Stand-alone image: vector

Routines supplied by role Numeric

Real does role Numeric, which provides the following routines:

(Numeric) method Numeric

Defined as:

multi method Numeric(Numeric:D: --> Numeric:D)
multi method Numeric(Numeric:U: --> Numeric:D)

The :D variant simply returns the invocant. The :U variant issues a warning about using an uninitialized value in numeric context and then returns

(Numeric) method Int

method Int(Numeric:D: --> Int:D)

If this Numeric is equivalent to a Real, return the equivalent of calling truncate on that Real to get an Int. Fail with X::Numeric::Real otherwise.

(Numeric) method Rat

method Rat(Numeric:D: Real $epsilon = 1.0e-6 --> Rat:D)

If this Numeric is equivalent to a Real, return a Rat which is within $epsilon of that Real's value. Fail with X::Numeric::Real otherwise.

(Numeric) method Num

method Num(Numeric:D: --> Num:D)

If this Numeric is equivalent to a Real, return that Real as a Num as accurately as is possible. Fail with X::Numeric::Real otherwise.

(Numeric) method narrow

method narrow(Numeric:D --> Numeric:D)

Returns the number converted to the narrowest type that can hold it without loss of precision.

say (4.0 + 0i).narrow.perl;     # OUTPUT: «4␤» 
say (4.0 + 0i).narrow.^name;    # OUTPUT: «Int␤» 

(Numeric) method ACCEPTS

multi method ACCEPTS(Numeric:D: $other)

Returns True if $other can be coerced to Numeric and is numerically equal to the invocant (or both evaluate to NaN).

(Numeric) routine log

multi sub    log(Numeric:DNumeric $base = e --> Numeric:D)
multi method log(Numeric:D: Numeric $base = e --> Numeric:D)

Calculates the logarithm to base $base. Defaults to the natural logarithm. Returns NaN if $base is negative. Throws an exception if $base is 1.

(Numeric) routine log10

multi sub    log10(Numeric:D  --> Numeric:D)
multi method log10(Numeric:D: --> Numeric:D)

Calculates the logarithm to base 10. Returns NaN for negative arguments and -Inf for 0.

(Numeric) routine exp

multi sub    exp(Numeric:DNumeric:D $base = e --> Numeric:D)
multi method exp(Numeric:D: Numeric:D $base = e --> Numeric:D)

Returns $base to the power of the number, or e to the power of the number if called without a second argument.

(Numeric) method roots

multi method roots(Numeric:D: Int:D $n --> Positional)

Returns a list of the $n complex roots, which evaluate to the original number when raised to the $nth power.

(Numeric) routine abs

multi sub    abs(Numeric:D  --> Real:D)
multi method abs(Numeric:D: --> Real:D)

Returns the absolute value of the number.

(Numeric) routine sqrt

multi sub    sqrt(Numeric:D --> Numeric:D)
multi method sqrt(Numeric:D --> Numeric:D)

Returns a square root of the number. For real numbers the positive square root is returned.

On negative real numbers, sqrt returns NaN rather than a complex number, in order to not confuse people who are not familiar with complex arithmetic. If you want to calculate complex square roots, coerce to Complex first, or use the roots method.

(Numeric) method conj

multi method conj(Numeric:D --> Numeric:D)

Returns the complex conjugate of the number. Returns the number itself for real numbers.

(Numeric) method Bool

multi method Bool(Numeric:D:)

Returns False if the number is equivalent to zero, and True otherwise.

(Numeric) method succ

method succ(Numeric:D:)

Returns the number incremented by one (successor).

(Numeric) method pred

method pred(Numeric:D:)

Returns the number decremented by one (predecessor).