class Seq

An iterable, lazy sequence of values

class Seq is Cool does Iterable does PositionalBindFailover { }

A Seq represents anything that can lazily produce a sequence of values. A Seq is born in a state where iterating it will consume the values. However, calling .cache on a Seq will return a List that is still lazy, but stores the generated values for later access. The same is true when assigning a Seq to an array.

A typical use case is method lines in IO::Handle, which could use a lot of memory if it stored all the lines read from the file. So

for open('README.md').lines -> $line {
    say $line;
}

won't keep all lines from the file in memory.

This implies that you cannot iterate the same Seq object twice (otherwise it couldn't throw away old values), so this dies:

my @a = 123;
my @b = <a b c>;
my \c = @a Z=> @b;
.say for c;
.say for c# fails 
CATCH { default { put .^name''.Str } };
# OUTPUT: «X::Seq::Consumed: This Seq has already been iterated, and its values consumed 
# (you might solve this by adding .cache on usages of the Seq, or 
# by assigning the Seq into an array)» 

A high-level construct to generate a Seq is gather/take, as well as many built-in methods like map and grep, low-level constructors to create a Seq from an iterator or from looping constructs are available too.

Caution: No program should ever assume a Seq may only be iterated once even if not cached by the program. Caching is a volatile state exposed to the developer as an optimization. The Seq may become cached by many operations, including calling perl on the Seq (if called prior to a non-cached iteration). If a program assumes a Seq can only iterate once, but then is later changed to call one of these operations during the loop, that assumption will fail.

Methods

method new

method new(Iterator:D $iter --> Seq:D)

Creates a new Seq object from the iterator passed as the single argument.

method iterator

method iterator(Seq:D: --> Iterator:D)

Returns the underlying iterator, and marks the invocant as consumed. If called on an already consumed sequence, throws an error of type X::Seq::Consumed.

method is-lazy

method is-lazy(Seq:D: --> Bool:D)

Returns True if the sequence is lazy and potentially infinite, and False otherwise. If called on an already consumed sequence, throws an error of type X::Seq::Consumed.

method eager

method eager(Seq:D: --> List:D)

Returns an eagerly evaluated List based on the invocant sequence, and marks it as consumed. If called on an already consumed sequence, throws an error of type X::Seq::Consumed.

my $s = lazy 1..5;
 
say $s.is-lazy# OUTPUT: «True␤» 
say $s.eager;   # OUTPUT: «(1 2 3 4 5)␤» 
 
say $s.eager;
CATCH {
    when X::Seq::Consumed {
        say 'Throws exception if already consumed';
    }
}
# OUTPUT: «Throws exception if already consumed␤» 

method from-loop

multi method from-loop(&body --> Seq:D)
multi method from-loop(&body&cond:$repeat --> Seq:D)
multi method from-loop(&body&cond&afterward --> Seq:D)

These methods create new Seq-based callbacks.

The first form produces an infinite Seq by calling &body each time a new element is requested, using the return value from &body as the item. This emulates (or implements) a loop { body } construct.

The second form calls &cond before each call to &body, and terminates the sequence if &cond returns a false value. If $repeat is set to a true value, the first call to &cond is omitted, and &body called right away. This emulates (or implements) while cond { body } and repeat { body } while cond loops.

The third form enables C-style looping by calling a third callback, &afterward, after each call to &body.

method sink

Defined as:

method sink(--> Nil)

Calls sink-all if it is an Iterator, sink if the Sequence is a list.

say (1 ... 1000).sink# OUTPUT: «Nil␤» 

This is something you might want to do for the side effects of producing those values.

method skip

Defined as:

multi method skip(Int() $n = 1 --> Seq)

Returns a Seq containing whatever is left of the invocant after throwing away $n of the next available values. Negative values of $n count as 0. Also can take a WhateverCode to indicate how many values to skip from the end. Will block on lazy Seqs until the requested number of values have been discarded.

say (1..5).map({$_}).skip;      # OUTPUT: «(2,3,4,5)␤» 
say (1..5).map({$_}).skip(3);   # OUTPUT: «(4,5)␤» 
say (1..5).map({$_}).skip(5);   # OUTPUT: «()␤» 
say (1..5).map({$_}).skip(-1);  # OUTPUT: «(1,2,3,4,5)␤» 
say (1..5).map({$_}).skip(*-3); # OUTPUT: «(3,4,5)␤» 

Type Graph

Type relations for Seq
perl6-type-graph Seq Seq Cool Cool Seq->Cool Iterable Iterable Seq->Iterable PositionalBindFailover PositionalBindFailover Seq->PositionalBindFailover Mu Mu Any Any Any->Mu Cool->Any

Expand above chart

Routines supplied by role Iterable

Seq does role Iterable, which provides the following routines:

(Iterable) method iterator

Defined as:

method iterator(--> Iterator:D)

Method stub that ensures all classes doing the Iterable role have a method iterator.

It is supposed to return an Iterator.

say (1..10).iterator;

(Iterable) method flat

Defined as:

method flat(--> Iterable)

Returns another Iterable that flattens out all iterables that the first one returns.

For example

say (<a b>'c').elems;         # OUTPUT: «2␤» 
say (<a b>'c').flat.elems;    # OUTPUT: «3␤» 

because <a b> is a List and thus iterable, so (<a b>, 'c').flat returns ('a', 'b', 'c'), which has three elems.

Note that the flattening is recursive, so ((("a", "b"), "c"), "d").flat returns ("a", "b", "c", "d"), but it does not flatten itemized sublists:

say ($('a''b'), 'c').perl;    # OUTPUT: «($("a", "b"), "c")␤» 

(Iterable) method lazy

Defined as:

method lazy(--> Iterable)

Returns a lazy iterable wrapping the invocant.

say (1 ... 1000).is-lazy;      # OUTPUT: «False␤» 
say (1 ... 1000).lazy.is-lazy# OUTPUT: «True␤» 

(Iterable) method hyper

Defined as:

method hyper(Int(Cool:$batch = 64Int(Cool:$degree = 4 --> Iterable)

Returns another Iterable that is potentially iterated in parallel, with a given batch size and degree of parallelism.

The order of elements is preserved.

say ([1..100].hyper.map({ $_ +1 }).list);

Use hyper in situations where it is OK to do the processing of items in parallel, and the output order should be kept relative to the input order. See race for situations where items are processed in parallel and the output order does not matter.

Options degree and batch

The degree option (short for "degree of parallelism") configures how many parallel workers should be started. To start 4 workers (e.g. to use at most 4 cores), pass :4degree to the hyper or race method. Note that in some cases, choosing a degree higher than the available CPU cores can make sense, for example I/O bound work or latency-heavy tasks like web crawling. For CPU-bound work, however, it makes no sense to pick a number higher than the CPU core count.

The batch size option configures the number of items sent to a given parallel worker at once. It allows for making a throughput/latency trade-off. If, for example, an operation is long-running per item, and you need the first results as soon as possible, set it to 1. That means every parallel worker gets 1 item to process at a time, and reports the result as soon as possible. In consequence, the overhead for inter-thread communication is maximized. In the other extreme, if you have 1000 items to process and 10 workers, and you give every worker a batch of 100 items, you will incur minimal overhead for dispatching the items, but you will only get the first results when 100 items are processed by the fastest worker (or, for hyper, when the worker getting the first batch returns.) Also, if not all items take the same amount of time to process, you might run into the situation where some workers are already done and sit around without being able to help with the remaining work. In situations where not all items take the same time to process, and you don't want too much inter-thread communication overhead, picking a number somewhere in the middle makes sense. Your aim might be to keep all workers about evenly busy to make best use of the resources available.

Blog post on the semantics of hyper and race

(Iterable) method race

Defined as:

method race(Int(Cool:$batch = 64Int(Cool:$degree = 4 --> Iterable)

Returns another Iterable that is potentially iterated in parallel, with a given batch size and degree of parallelism (number of parallel workers).

Unlike hyper, race does not preserve the order of elements.

say ([1..100].race.map({ $_ +1 }).list);

Use race in situations where it is OK to do the processing of items in parallel, and the output order does not matter. See hyper for situations where you want items processed in parallel and the output order should be kept relative to the input order.

Blog post on the semantics of hyper and race

See hyper for an explanation of :$batch and :$degree.

Routines supplied by role PositionalBindFailover

Seq does role PositionalBindFailover, which provides the following routines:

(PositionalBindFailover) method cache

method cache(PositionalBindFailover:D: --> List:D)

Returns a List based on the iterator method, and caches it. Subsequent calls to cache always return the same List object.

(PositionalBindFailover) method list

method list(PositionalBindFailover:D: --> List:D)

Returns a List based on the iterator method without caching it.

(PositionalBindFailover) method iterator

method iterator(PositionalBindFailover:D:{ ... }

This method stub ensure that a class implementing role PositionalBindFailover provides an iterator method.

Routines supplied by class Cool

Seq inherits from class Cool, which provides the following routines:

(Cool) routine abs

Defined as:

sub abs(Numeric() $x)
method abs()

Coerces the invocant (or in the sub form, the argument) to Numeric and returns the absolute value (that is, a non-negative number).

say (-2).abs;       # OUTPUT: «2␤» 
say abs "6+8i";     # OUTPUT: «10␤» 

(Cool) method conj

Defined as:

method conj()

Coerces the invocant to Numeric and returns the complex conjugate (that is, the number with the sign of the imaginary part negated).

say (1+2i).conj;        # OUTPUT: «1-2i␤» 

(Cool) routine sqrt

Defined as:

sub sqrt(Numeric(Cool$x)
method sqrt()

Coerces the invocant to Numeric (or in the sub form, the argument) and returns the square root, that is, a non-negative number that, when multiplied with itself, produces the original number.

say 4.sqrt;             # OUTPUT: «2␤» 
say sqrt(2);            # OUTPUT: «1.4142135623731␤» 

(Cool) method sign

Defined as:

method sign()

Coerces the invocant to Numeric and returns its sign, that is, 0 if the number is 0, 1 for positive and -1 for negative values.

say 6.sign;             # OUTPUT: «1␤» 
say (-6).sign;          # OUTPUT: «-1␤» 
say "0".sign;           # OUTPUT: «0␤» 

(Cool) method rand

Defined as:

method rand()

Coerces the invocant to Num and returns a pseudo-random value between zero and the number.

say 1e5.rand;           # OUTPUT: «33128.495184283␤» 

(Cool) routine sin

Defined as:

sub sin(Numeric(Cool))
method sin()

Coerces the invocant (or in the sub form, the argument) to Numeric, interprets it as radians, returns its sine.

say sin(0);             # OUTPUT: «0␤» 
say sin(pi/4);          # OUTPUT: «0.707106781186547␤» 
say sin(pi/2);          # OUTPUT: «1␤» 

Note that Perl 6 is no computer algebra system, so sin(pi) typically does not produce an exact 0, but rather a very small floating-point number.

(Cool) routine asin

Defined as:

sub asin(Numeric(Cool))
method asin()

Coerces the invocant (or in the sub form, the argument) to Numeric, and returns its arc-sine in radians.

say 0.1.asin;               # OUTPUT: «0.10016742116156␤» 
say asin(0.1);              # OUTPUT: «0.10016742116156␤» 

(Cool) routine cos

Defined as:

sub cos(Numeric(Cool))
method cos()

Coerces the invocant (or in sub form, the argument) to Numeric, interprets it as radians, returns its cosine.

say 0.cos;                  # OUTPUT: «1␤» 
say pi.cos;                 # OUTPUT: «-1␤» 
say cos(pi/2);              # OUTPUT: «6.12323399573677e-17␤» 

(Cool) routine acos

Defined as:

sub acos(Numeric(Cool))
method acos()

Coerces the invocant (or in sub form, the argument) to Numeric, and returns its arc-cosine in radians.

say 1.acos;                 # OUTPUT: «0␤» 
say acos(-1);               # OUTPUT: «3.14159265358979␤» 

(Cool) routine tan

Defined as:

sub tan(Numeric(Cool))
method tan()

Coerces the invocant (or in sub form, the argument) to Numeric, interprets it as radians, returns its tangent.

say tan(3);                 # OUTPUT: «-0.142546543074278␤» 
say 3.tan;                  # OUTPUT: «-0.142546543074278␤» 

(Cool) routine atan

Defined as:

sub atan(Numeric(Cool))
method atan()

Coerces the invocant (or in sub form, the argument) to Numeric, and returns its arc-tangent in radians.

say atan(3);                # OUTPUT: «1.24904577239825␤» 
say 3.atan;                 # OUTPUT: «1.24904577239825␤» 

(Cool) routine atan2

Defined as:

sub atan2(Numeric() $xNumeric() $y = 1e0)
method atan2($y = 1e0)

Coerces the arguments (including the invocant in the method form) to Numeric, and returns their two-argument arc-tangent in radians.

say atan2(3);               # OUTPUT: «1.24904577239825␤» 
say 3.atan2;                # OUTPUT: «1.24904577239825␤» 

(Cool) routine sec

Defined as:

sub sec(Numeric(Cool))
method sec()

Coerces the invocant (or in sub form, its argument) to Numeric, interprets it as radians, returns its secant, that is, the reciprocal of its cosine.

say 45.sec;                 # OUTPUT: «1.90359440740442␤» 
say sec(45);                # OUTPUT: «1.90359440740442␤» 

(Cool) routine asec

Defined as:

sub asec(Numeric(Cool))
method asec()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its arc-secant in radians.

say 1.asec;                 # OUTPUT: «0␤» 
say sqrt(2).asec;           # OUTPUT: «0.785398163397448␤» 

(Cool) routine cosec

Defined as:

sub cosec(Numeric(Cool))
method cosec()

Coerces the invocant (or in sub form, its argument) to Numeric, interprets it as radians, returns its cosecant, that is, the reciprocal of its sine.

say 0.45.cosec;             # OUTPUT: «2.29903273150897␤» 
say cosec(0.45);            # OUTPUT: «2.29903273150897␤» 

(Cool) routine acosec

Defined as:

sub acosec(Numeric(Cool))
method acosec()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its arc-cosecant in radians.

say 45.acosec;              # OUTPUT: «0.0222240516182672␤» 
say acosec(45)              # OUTPUT: «0.0222240516182672␤» 

(Cool) routine cotan

Defined as:

sub cotan(Numeric(Cool))
method cotan()

Coerces the invocant (or in sub form, its argument) to Numeric, interprets it as radians, returns its cotangent, that is, the reciprocal of its tangent.

say 45.cotan;               # OUTPUT: «0.617369623783555␤» 
say cotan(45);              # OUTPUT: «0.617369623783555␤» 

(Cool) routine acotan

Defined as:

sub acotan(Numeric(Cool))
method acotan()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its arc-cotangent in radians.

say 45.acotan;              # OUTPUT: «0.0222185653267191␤» 
say acotan(45)              # OUTPUT: «0.0222185653267191␤» 

(Cool) routine sinh

Defined as:

sub sinh(Numeric(Cool))
method sinh()

Coerces the invocant (or in method form, its argument) to Numeric, and returns its Sine hyperbolicus.

say 1.sinh;                 # OUTPUT: «1.1752011936438␤» 
say sinh(1);                # OUTPUT: «1.1752011936438␤» 

(Cool) routine asinh

Defined as:

sub asinh(Numeric(Cool))
method asinh()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Inverse Sine hyperbolicus.

say 1.asinh;                # OUTPUT: «0.881373587019543␤» 
say asinh(1);               # OUTPUT: «0.881373587019543␤» 

(Cool) routine cosh

Defined as:

sub cosh(Numeric(Cool))
method cosh()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Cosine hyperbolicus.

say cosh(0.5);              # OUTPUT: «1.12762596520638␤» 

(Cool) routine acosh

Defined as:

sub acosh(Numeric(Cool))
method acosh()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Inverse Cosine hyperbolicus.

say acosh(45);              # OUTPUT: «4.4996861906715␤» 

(Cool) routine tanh

Defined as:

sub tanh(Numeric(Cool))
method tanh()

Coerces the invocant (or in sub form, its argument) to Numeric, interprets it as radians and returns its Tangent hyperbolicus.

say tanh(0.5);              # OUTPUT: «0.46211715726001␤» 
say tanh(atanh(0.5));       # OUTPUT: «0.5␤» 

(Cool) routine atanh

Defined as:

sub atanh(Numeric(Cool))
method atanh()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Inverse tangent hyperbolicus.

say atanh(0.5);             # OUTPUT: «0.549306144334055␤» 

(Cool) routine sech

Defined as:

sub sech(Numeric(Cool))
method sech()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Secant hyperbolicus.

say 0.sech;                 # OUTPUT: «1␤» 

(Cool) routine asech

Defined as:

sub asech(Numeric(Cool))
method asech()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Inverse hyperbolic secant.

say 0.8.asech;              # OUTPUT: «0.693147180559945␤» 

(Cool) routine cosech

Defined as:

sub cosech(Numeric(Cool))
method cosech()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Hyperbolic cosecant.

say cosech(pi/2);           # OUTPUT: «0.434537208094696␤» 

(Cool) routine acosech

Defined as:

sub acosech(Numeric(Cool))
method acosech()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Inverse hyperbolic cosecant.

say acosech(4.5);           # OUTPUT: «0.220432720979802␤» 

(Cool) routine cotanh

Defined as:

sub cotanh(Numeric(Cool))
method cotanh()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Hyperbolic cotangent.

say cotanh(pi);             # OUTPUT: «1.00374187319732␤» 

(Cool) routine acotanh

Defined as:

sub acotanh(Numeric(Cool))
method acotanh()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns its Inverse hyperbolic cotangent.

say acotanh(2.5);           # OUTPUT: «0.423648930193602␤» 

(Cool) routine cis

Defined as:

sub cis(Numeric(Cool))
method cis()

Coerces the invocant (or in sub form, its argument) to Numeric, and returns cos(argument) + i*sin(argument).

say cis(pi/4);              # OUTPUT: «0.707106781186548+0.707106781186547i␤» 

(Cool) routine log

Defined as:

multi sub log(Numeric(Cool$numberNumeric(Cool$base?)
multi method log(Cool:D: Cool:D $base?)

Coerces the arguments (including the invocant in the method form) to Numeric, and returns its Logarithm to base $base, or to base e (Euler's Number) if no base was supplied (Natural logarithm). Returns NaN if $base is negative. Throws an exception if $base is 1.

say (e*e).log;              # OUTPUT: «2␤» 

(Cool) routine log10

Defined as:

multi sub log10(Cool(Numeric))
multi method log10()

Coerces the invocant (or in the sub form, the invocant) to Numeric, and returns its Logarithm to base 10, that is, a number that approximately produces the original number when raised to the power of 10. Returns NaN for negative arguments and -Inf for 0.

say log10(1001);            # OUTPUT: «3.00043407747932␤» 

(Cool) routine exp

Defined as:

multi sub exp(Cool:D $powCool:D $base?)
multi method exp(Cool:D: Cool:D $base?)

Coerces the arguments (including the invocant in the method from) to Numeric, and returns $base raised to the power of the first number. If no $base is supplied, e (Euler's Number) is used.

say 0.exp;      # OUTPUT: «1␤» 
say 1.exp;      # OUTPUT: «2.71828182845905␤» 
say 10.exp;     # OUTPUT: «22026.4657948067␤» 

(Cool) method unpolar

Defined as:

method unpolar(Numeric(Cool))

Coerces the arguments (including the invocant in the method form) to Numeric, and returns a complex number from the given polar coordinates. The invocant (or the first argument in sub form) is the magnitude while the argument (i.e. the second argument in sub form) is the angle. The angle is assumed to be in radians.

say sqrt(2).unpolar(pi/4);      # OUTPUT: «1+1i␤» 

(Cool) routine round

Defined as:

multi sub round(Numeric(Cool))
multi method round(Cool:D: $unit = 1)

Coerces the invocant (or in sub form, its argument) to Numeric, and rounds it to the unit of $unit. If $unit is 1, rounds to the nearest integer.

say 1.7.round;          # OUTPUT: «2␤» 
say 1.07.round(0.1);    # OUTPUT: «1.1␤» 
say 21.round(10);       # OUTPUT: «20␤» 

Always rounds up if the number is at mid-point:

say (−.5 ).round;       # OUTPUT: «0␤» 
say ( .5 ).round;       # OUTPUT: «1␤» 
say (−.55).round(.1);   # OUTPUT: «-0.5␤» 
say ( .55).round(.1);   # OUTPUT: «0.6␤» 

Pay attention to types when using this method, as ending up with the wrong type may affect the precision you seek to achieve. For Real types, the type of the result is the type of the argument (Complex argument gets coerced to Real, ending up a Num). If rounding a Complex, the result is Complex as well, regardless of the type of the argument.

9930972392403501.round(1)      .perl.say# OUTPUT: «9930972392403501␤» 
9930972392403501.round(1e0)    .perl.say# OUTPUT: «9.9309723924035e+15␤» 
9930972392403501.round(1e0).Int.perl.say# OUTPUT: «9930972392403500␤» 

(Cool) routine floor

Defined as:

multi sub floor(Numeric(Cool))
multi method floor

Coerces the invocant (or in sub form, its argument) to Numeric, and rounds it downwards to the nearest integer.

say "1.99".floor;       # OUTPUT: «1␤» 
say "-1.9".floor;       # OUTPUT: «-2␤» 
say 0.floor;            # OUTPUT: «0␤» 

(Cool) method fmt

Defined as:

method fmt($format = '%s')

Equivalent to calling sprintf with $format as format and the invocant as the second argument. The $format will be coerced to Stringy and defaults to '%s'

(Cool) routine ceiling

Defined as:

multi sub ceiling(Numeric(Cool))
multi method ceiling

Coerces the invocant (or in sub form, its argument) to Numeric, and rounds it upwards to the nearest integer.

say "1".ceiling;        # OUTPUT: «1␤» 
say "-0.9".ceiling;     # OUTPUT: «0␤» 
say "42.1".ceiling;     # OUTPUT: «43␤» 

(Cool) routine truncate

Defined as:

multi sub truncate(Numeric(Cool))
multi method truncate()

Coerces the invocant (or in sub form, its argument) to Numeric, and rounds it towards zero.

say 1.2.truncate;       # OUTPUT: «1␤» 
say truncate -1.2;      # OUTPUT: «-1␤» 

(Cool) routine ord

Defined as:

sub ord(Str(Cool))
method ord()

Coerces the invocant (or in sub form, its argument) to Str, and returns the Unicode code point number of the first code point.

say 'a'.ord;            # OUTPUT: «97␤» 

The inverse operation is chr.

Mnemonic: returns an ordinal number

(Cool) method path

Defined as:

method path()

DEPRECATED. Existed only in the Rakudo implementation and isn't part of any language released. Will issue deprecation warnings in future language versions and eventually will be removed entirely.

Stringifies the invocant and converts it to IO::Path object. Use the .IO method instead.

(Cool) routine chr

Defined as:

sub chr(Int(Cool))
method chr()

Coerces the invocant (or in sub form, its argument) to Int, interprets it as a Unicode code points, and returns a string made of that code point.

say '65'.chr;       # OUTPUT: «A␤» 

The inverse operation is ord.

Mnemonic: turns an integer into a character.

(Cool) routine chars

Defined as:

sub chars(Str(Cool))
method chars()

Coerces the invocant (or in sub form, its argument) to Str, and returns the number of characters in the string. Please note that on the JVM, you currently get codepoints instead of graphemes.

say 'møp'.chars;    # OUTPUT: «3␤» 
say 'ã̷̠̬̊'.chars;     # OUTPUT: «1␤» 
say '👨‍👩‍👧‍👦🏿'.chars;    # OUTPUT: «1␤» 

Graphemes are user visible characters. That is, this is what the user thinks of as a “character”.

Graphemes can contain more than one codepoint. Typically the number of graphemes and codepoints differs when Prepend or Extend characters are involved (also known as Combining characters), but there are many other cases when this may happen. Another example is \c[ZWJ] (Zero-width joiner).

You can check Grapheme_Cluster_Break property of a character in order to see how it is going to behave:

say ã̷̠̬̊.uniprops(Grapheme_Cluster_Break); # OUTPUT: «(Other Extend Extend Extend Extend)␤» 
say 👨‍👩‍👧‍👦🏿.uniprops(Grapheme_Cluster_Break); # OUTPUT: «(E_Base_GAZ ZWJ E_Base_GAZ ZWJ E_Base_GAZ ZWJ E_Base_GAZ E_Modifier)␤» 

You can read more about graphemes in the Unicode Standard, which Perl 6 tightly follows, using a method called NFG, normal form graphemes for efficiently representing them.

(Cool) routine codes

Defined as:

sub codes(Str(Cool))
method codes()

Coerces the invocant (or in sub form, its argument) to Str, and returns the number of Unicode code points.

say 'møp'.codes;    # OUTPUT: «3␤» 

The same result will be obtained with

say +'møp'.ords;    # OUTPUT: «3␤» 

ords first obtains the actual codepoints, so there might be a difference in speed.

(Cool) routine flip

Defined as:

sub flip(Str(Cool))
method flip()

Coerces the invocant (or in sub form, its argument) to Str, and returns a reversed version.

say 421.flip;       # OUTPUT: «124␤» 

(Cool) routine trim

Defined as:

sub trim(Str(Cool))
method trim()

Coerces the invocant (or in sub form, its argument) to Str, and returns the string with both leading and trailing whitespace stripped.

my $stripped = '  abc '.trim;
say "<$stripped>";          # OUTPUT: «<abc>␤» 

(Cool) routine trim-leading

Defined as:

sub trim-leading(Str(Cool))
method trim-leading()

Coerces the invocant (or in sub form, its argument) to Str, and returns the string with leading whitespace stripped.

my $stripped = '  abc '.trim-leading;
say "<$stripped>";          # OUTPUT: «<abc >␤» 

(Cool) routine trim-trailing

Defined as:

sub trim-trailing(Str(Cool))
method trim-trailing()

Coerces the invocant (or in sub form, its argument) to Str, and returns the string with trailing whitespace stripped.

my $stripped = '  abc '.trim-trailing;
say "<$stripped>";          # OUTPUT: «<  abc>␤» 

(Cool) routine lc

Defined as:

sub lc(Str(Cool))
method lc()

Coerces the invocant (or in sub form, its argument) to Str, and returns it case-folded to lower case.

say "ABC".lc;       # OUTPUT: «abc␤» 

(Cool) routine uc

Defined as:

sub uc(Str(Cool))
method uc()

Coerces the invocant (or in sub form, its argument) to Str, and returns it case-folded to upper case (capital letters).

say "Abc".uc;       # OUTPUT: «ABC␤» 

(Cool) routine fc

Defined as:

sub fc(Str(Cool))
method fc()

Coerces the invocant (or in sub form, its argument) to Str, and returns the result a Unicode "case fold" operation suitable for doing caseless string comparisons. (In general, the returned string is unlikely to be useful for any purpose other than comparison.)

say "groß".fc;       # OUTPUT: «gross␤» 

(Cool) routine tc

Defined as:

sub tc(Str(Cool))
method tc()

Coerces the invocant (or in sub form, its argument) to Str, and returns it with the first letter case-folded to title case (or where not available, upper case).

say "abC".tc;       # OUTPUT: «AbC␤» 

(Cool) routine tclc

Defined as:

sub tclc(Str(Cool))
method tclc()

Coerces the invocant (or in sub form, its argument) to Str, and returns it with the first letter case-folded to title case (or where not available, upper case), and the rest of the string case-folded to lower case.

say 'abC'.tclc;     # OUTPUT: «Abc␤» 

(Cool) routine wordcase

Defined as:

sub wordcase(Str(Cool$input:&filter = &tclcMu :$where = True)
method wordcase(:&filter = &tclcMu :$where = True)

Coerces the invocant (or in sub form, the first argument) to Str, and filters each word that smartmatches against $where through the &filter. With the default filter (first character to upper case, rest to lower) and matcher (which accepts everything), this title-cases each word:

say "perl 6 programming".wordcase;      # OUTPUT: «Perl 6 Programming␤» 

With a matcher:

say "have fun working on perl".wordcase(:where({ .chars > 3 }));
                                        # Have fun Working on Perl 

With a customer filter too:

say "have fun working on perl".wordcase(:filter(&uc), :where({ .chars > 3 }));
                                        # HAVE fun WORKING on PERL 

(Cool) routine samecase

Defined as:

sub samecase(Cool $stringCool $pattern)
method samecase(Cool:D: Cool $pattern)

Coerces the invocant (or in sub form, the first argument) to Str, and returns a copy of $string with case information for each individual character changed according to $pattern.

Note: The pattern string can contain three types of characters, i.e. uppercase, lowercase and caseless. For a given character in $pattern its case information determines the case of the corresponding character in the result.

If $string is longer than $pattern, the case information from the last character of $pattern is applied to the remaining characters of $string.

say "perL 6".samecase("A__a__"); # OUTPUT: «Perl 6␤» 
say "pERL 6".samecase("Ab");     # OUTPUT: «Perl 6␤» 

(Cool) routine uniprop

Defined as:

multi sub uniprop(Str:D|c)
multi sub uniprop(Int:D $code)
multi sub uniprop(Int:D $codeStringy:D $propname)
multi method uniprop(|c)

Returns the unicode property of the first character. If no property is specified returns the General Category. Returns a Bool for Boolean properties.

say 'a'.uniprop;               # OUTPUT: «Ll␤» 
say '1'.uniprop;               # OUTPUT: «Nd␤» 
say 'a'.uniprop('Alphabetic'); # OUTPUT: «True␤» 
say '1'.uniprop('Alphabetic'); # OUTPUT: «False␤» 

(Cool) sub uniprops

Defined as:

sub uniprops(Str:D $strStringy:D $propname = "General_Category")

Interprets the invocant as a Str, and returns the unicode property for each character as a Seq. If no property is specified returns the General Category. Returns a Bool for Boolean properties. Similar to uniprop

(Cool) routine uniname

Defined as:

sub uniname(Str(Cool--> Str)
method uniname(--> Str)

Interprets the invocant / first argument as a Str, and returns the Unicode codepoint name of the first codepoint of the first character. See uninames for a routine that works with multiple codepoints, and uniparse for the opposite direction.

# Camelia in Unicode 
say »ö«.uniname;
# OUTPUT: «"RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK"␤» 
say "Ḍ̇".uniname# Note, doesn't show "COMBINING DOT ABOVE" 
# OUTPUT: «"LATIN CAPITAL LETTER D WITH DOT BELOW"␤» 
 
# Find the char with the longest Unicode name. 
say (0..0x1FFFF).sort(*.uniname.chars)[*-1].chr.uniname;
# OUTPUT: ««ARABIC LIGATURE UIGHUR KIRGHIZ YEH WITH HAMZA ABOVE WITH ALEF MAKSURA INITIAL FORM␤»␤» 

(Cool) routine uninames

Defined as:

sub uninames(Str:D)
method uninames()

Returns of a Seq of Unicode names for the all the codepoints in the Str provided.

say »ö«.uninames.perl;
# OUTPUT: «("RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK", "LATIN SMALL LETTER O WITH DIAERESIS", "LEFT-POINTING DOUBLE ANGLE QUOTATION MARK").Seq␤» 

Note this example, which gets a Seq where each element is a Seq of all the codepoints in that character.

say "Ḍ̇'oh".comb>>.uninames.perl;
# OUTPUT: «(("LATIN CAPITAL LETTER D WITH DOT BELOW", "COMBINING DOT ABOVE").Seq, ("APOSTROPHE",).Seq, ("LATIN SMALL LETTER O",).Seq, ("LATIN SMALL LETTER H",).Seq)␤» 

See uniparse for the opposite direction.

(Cool) routine unimatch

Defined as:

multi sub unimatch(Str:D $str|c)
multi unimatch(Int:D $codeStringy:D $pvalnameStringy:D $propname = $pvalname)

Checks if the given integer codepoint or the first letter of the string given have a unicode property equal to the value you give. If you supply the Unicode property to be checked it will only return True if that property matches the given value.

say unimatch 'A''Latin';           # OUTPUT: «True␤» 
say unimatch 'A''Latin''Script'# OUTPUT: «True␤» 
say unimatch 'A''Ll';              # OUTPUT: «True␤» 

(Cool) routine chop

Defined as:

sub chop(Str(Cool))
method chop()

Coerces the invocant (or in sub form, its argument) to Str, and returns it with the last character removed.

say 'perl'.chop;                        # OUTPUT: «per␤» 

(Cool) routine chomp

Defined as:

sub chomp(Str(Cool))
method chomp()

Coerces the invocant (or in sub form, its argument) to Str, and returns it with the last character removed, if it is a logical newline.

say 'ab'.chomp.chars;                   # OUTPUT: «2␤» 
say "a\n".chomp.chars;                  # OUTPUT: «1␤» 

(Cool) routine substr

Defined as:

sub substr(Str(Cool$str|c)
method substr(|c)

Coerces the invocant (or in the sub form, the first argument) to Str, and calls Str.substr with the arguments.

(Cool) routine substr-rw

Defined as:

multi method substr-rw(|) is rw
multi sub substr-rw(|) is rw

Coerces the invocant (or in the sub form, the first argument) to Str, and calls Str.substr-rw with the arguments.

(Cool) routine ords

Defined as:

sub ords(Str(Cool$str)
method ords()

Coerces the invocant (or in the sub form, the first argument) to Str, and returns a list of Unicode codepoints for each character.

say "Camelia".ords;              # OUTPUT: «67 97 109 101 108 105 97␤» 
say ords 10;                     # OUTPUT: «49 48␤» 

This is the list-returning version of ord. The inverse operation in chrs. If you are only interested in the number of codepoints, codes is a possibly faster option.

(Cool) routine chrs

Defined as:

sub chrs(*@codepoints --> Str:D)
method chrs()

Coerces the invocant (or in the sub form, the argument list) to a list of integers, and returns the string created by interpreting each integer as a Unicode codepoint, and joining the characters.

say <67 97 109 101 108 105 97>.chrs;   # OUTPUT: «Camelia␤» 

This is the list-input version of chr. The inverse operation is ords.

(Cool) routine split

Defined as:

multi sub    split(  Str:D $delimiterStr(Cool$input$limit = Inf:$k:$v:$kv:$p:$skip-empty)
multi sub    split(Regex:D $delimiterStr(Cool$input$limit = Inf:$k:$v:$kv:$p:$skip-empty)
multi sub    split(@delimitersStr(Cool$input$limit = Inf:$k:$v:$kv:$p:$skip-empty)
multi method split(  Str:D $delimiter$limit = Inf:$k:$v:$kv:$p:$skip-empty)
multi method split(Regex:D $delimiter$limit = Inf:$k:$v:$kv:$p:$skip-empty)
multi method split(@delimiters$limit = Inf:$k:$v:$kv:$p:$skip-empty)

[1]

Coerces the invocant (or in the sub form, the second argument) to Str, and splits it into pieces based on delimiters found in the string.

If $delimiter is a string, it is searched for literally and not treated as a regex. You can also provide multiple delimiters by specifying them as a list; mixing Cool and Regex objects is OK.

say split(';'"a;b;c").perl;               # OUTPUT: «("a", "b", "c")␤» 
say split(';'"a;b;c"2).perl;            # OUTPUT: «("a", "b;c").Seq␤» 
 
say split(';'"a;b;c,d").perl;             # OUTPUT: «("a", "b", "c,d")␤» 
say split(/\;/"a;b;c,d").perl;            # OUTPUT: «("a", "b", "c,d")␤» 
say split(/<[;,]>/"a;b;c,d").perl;        # OUTPUT: «("a", "b", "c", "d")␤» 
 
say split(['a', /b+/4], '1a2bb345').perl# OUTPUT: «("1", "2", "3", "5")␤» 

By default, split omits the matches, and returns a list of only those parts of the string that did not match. Specifying one of the :k, :v, :kv, :p adverbs changes that. Think of the matches as a list that is interleaved with the non-matching parts.

The :v interleaves the values of that list, which will be either Match objects, if a Regex was used as a matcher in the split, or Str objects, if a Cool was used as matcher. If multiple delimiters are specified, Match objects will be generated for all of them, unless all of the delimiters are Cool.

say 'abc'.split(/b/:v);               # OUTPUT: «(a 「b」 c)␤» 
say 'abc'.split('b':v);               # OUTPUT: «(a b c)␤» 

:k interleaves the keys, that is, the indexes:

say 'abc'.split(/b/:k);               # OUTPUT: «(a 0 c)␤» 

:kv adds both indexes and matches:

say 'abc'.split(/b/:kv);               # OUTPUT: «(a 0 「b」 c)␤» 

and :p adds them as Pairs, using the same types for values as :v does:

say 'abc'.split(/b/:p);               # OUTPUT: «(a 0 => 「b」 c)␤» 
say 'abc'.split('b':p);               # OUTPUT: «(a 0 => b c)␤» 

You can only use one of the :k, :v, :kv, :p adverbs in a single call to split.

Note that empty chunks are not removed from the result list. For that behavior, use the :skip-empty named argument:

say ("f,,b,c,d".split: /","/             ).perl;  # OUTPUT: «("f", "", "b", "c", "d")␤» 
say ("f,,b,c,d".split: /","/:skip-empty).perl;  # OUTPUT: «("f", "b", "c", "d")␤» 

(Cool) routine lines

Defined as:

sub lines(Str(Cool))
method lines()

Coerces the invocant (and in sub form, the argument) to Str, decomposes it into lines (with the newline characters stripped), and returns the list of lines.

say lines("a\nb\n").join('|');          # OUTPUT: «a|b␤» 
say "some\nmore\nlines".lines.elems;    # OUTPUT: «3␤» 

This method can be used as part of an IO::Path to process a file line-by-line, since IO::Path objects inherit from Cool, e.g.:

for 'huge-csv'.IO.lines -> $line {
    # Do something with $line 
}
 
# or if you'll be processing later 
my @lines = 'huge-csv'.IO.lines;

Without any arguments, sub lines operates on $*ARGFILES, which defaults to $*IN in the absence of any filenames.

To modify values in place use is copy to force a writable container.

for $*IN.lines -> $_ is copy { s/(\w+)/{$0 ~ $0}/.say }

(Cool) method words

Defined as:

method words(Cool:D: |c)

Coerces the invocant (or first argument, if it is called as a subroutine) to Str, and returns a list of words that make up the string (and if $limit is supplied and is not equal to Inf, only the first $limit words).

say <The quick brown fox>.words.join('|');      # OUTPUT: «The|quick|brown|fox␤» 
say <The quick brown fox>.words(2).join('|');   # OUTPUT: «The|quick␤» 

Cool is the base class for many other classes, and some of them, like Match, can be converted to a string. This is what happens in this case:

say ( "easy come, easy goes" ~~ m:g/(ea\w+)/).words(Inf);
# OUTPUT: «(easy easy)␤» 
say words"easy come, easy goes" ~~ m:g/(ea\w+)/ , ∞);
# OUTPUT: «(easy easy)␤» 

The example above shows the two ways words can be invoked, with the first argument turned into invocant by its signature. Of course, Inf is the default value of the second argument, so in both cases (and forms) it can be simply omited.

Only whitespace (including no-break space) counts as word boundaries

say <Don't we ♥ Perl 6>.words.join('|');# OUTPUT: «Don't|we|♥|Perl|6␤» 

In this case, Perl 6 includes an (visible only in the source) no-break space; words still splits the (resulting) Str on it, even if the original array only had 4 elements:

say <Don't we ♥ Perl 6>.join("|");# OUTPUT: «Don't|we|♥|Perl 6␤» 

Please see Str.words for more examples.

(Cool) routine comb

Defined as:

multi sub comb(Regex $matcherStr(Cool$input$limit = * --> Seq)
multi method comb(Regex $matcher$limit = * --> Seq)

Returns all (or if supplied, at most $limit) matches of the invocant (method form) or the second argument (sub form) against the Regex as a list of strings.

say "6 or 12".comb(/\d+/).join("");           # OUTPUT: «6, 12␤» 

(Cool) method contains

Defined as:

method contains(Cool:D: |c)

Coerces the invocant Str, and calls Str.contains on it. Please refer to that version of the method for arguments and general syntax.

say 123.contains("2")# OUTPUT: «True␤» 

Since Int is a subclass of Cool, 123 is coerced to a Str and then contains is called on it.

say (1,1* + * … * > 250).contains(233)# OUTPUT: «True␤» 

Seqs are also subclasses of Cool, and they are stringified to a comma-separated form. In this case we are also using an Int, which is going to be stringified also; "233" is included in that sequence, so it returns True. Please note that this sequence is not lazy; the stringification of lazy sequences does not include each and every one of their components for obvious reasons.

(Cool) routine index

Defined as:

multi sub    index(Str(Cool$sStr:D $needleInt(Cool$startpos = 0 --> Int)
multi method index(Str(Cool$needleInt(Cool$startpos = 0 --> Int)

Coerces the first two arguments (in method form, also counting the invocant) to Str, and searches for $needle in the string starting from $startpos. It returns the offset into the string where $needle was found, and an undefined value if it was not found.

See the documentation in type Str for examples.

(Cool) routine rindex

Defined as:

multi sub    rindex(Str(Cool$haystackStr(Cool$needleInt(Cool$startpos = $haystack.chars)
multi method rindex(Str(Cool$haystack: Str(Cool$needleInt(Cool$startpos = $haystack.chars)

Coerces the first two arguments (including the invocant in method form) to Str and $startpos to Int, and returns the last position of $needle in $haystack not after $startpos. Returns an undefined value if $needle wasn't found.

See the documentation in type Str for examples.

(Cool) method match

Defined as:

multi method match(Cool:D: $target*%adverbs)

Coerces the invocant to Str and calls the method match on it.

(Cool) method fmt

Defined as:

method fmt($format = '%s' --> Str:D)

Uses $format to return a formatted representation of the invocant.

For more information about formats strings, see sprintf.

say 11.fmt('This Int equals %03d');               # OUTPUT: «This Int equals 011␤» 
say '16'.fmt('Hexadecimal %x');                   # OUTPUT: «Hexadecimal 10␤» 

(Cool) routine roots

Defined as:

multi sub roots(Numeric(Cool$xInt(Cool$n)
multi method roots(Int(Cool$n)

Coerces the first argument (and in method form, the invocant) to Numeric and the second ($n) to Int, and produces a list of $n Complex $n-roots, which means numbers that, raised to the $nth power, approximately produce the original number.

For example

my $original = 16;
my @roots = $original.roots(4);
say @roots;
 
for @roots -> $r {
    say abs($r ** 4 - $original);
}
 
# OUTPUT:«2+0i 1.22464679914735e-16+2i -2+2.44929359829471e-16i -3.67394039744206e-16-2i␤» 
# OUTPUT:«1.77635683940025e-15␤» 
# OUTPUT:«4.30267170434156e-15␤» 
# OUTPUT:«8.03651692704705e-15␤» 
# OUTPUT:«1.04441561648202e-14␤» 

(Cool) method match

Defined as:

method match(|)

Coerces the invocant to Stringy and calls Str.match.

(Cool) method subst

Defined as:

method subst(|)

Coerces the invocant to Stringy and calls Str.subst.

(Cool) method trans

Defined as:

method trans(|)

Coerces the invocant to Str and calls Str.trans

(Cool) method IO

Defined as:

method IO(--> IO::Path:D)

Coerces the invocant to IO::Path.

.say for '.'.IO.dir;        # gives a directory listing 

(Cool) routine EVAL

Defined as:

method EVAL(*%_)
sub EVAL($code where Cool|Blob:$lang = 'perl6')

The method form calls subroutine form with invocant as $code, passing along named args, if any. Subroutine form coerces Cool $code to Str. If $code is a Blob, it'll be processed using the same encoding as the $lang compiler would: for perl6 $lang, uses utf-8; for Perl5, processes using the same rules as perl.

This works as-is with a literal string parameter. More complex input, such as a variable or string with embedded code, is illegal by default. This can be overridden in any of several ways:

use MONKEY-SEE-NO-EVAL# Or... 
use MONKEY;             # shortcut that turns on all MONKEY pragmas 
use Test;
 
# any of the above allows: 
EVAL "say { 5 + 5 }";   # OUTPUT: «10␤» 

In case the MONKEY-SEE-NO-EVAL pragma is not activated, the compiler will complain with a EVAL is a very dangerous function!!! exception. And it is essentially right, since that will run arbitrary code with the same permissions as the program. You should take care of cleaning the code that is going to pass through EVAL if you activate the MONKEY-SEE-NO-EVAL pragma.

Please note that you can interpolate to create routine names using quotation, as can be seen in this example or other ways to interpolate to create identifier names. This only works, however, for already declared functions and other objects and is thus safer to use.

Symbols in the current lexical scope are visible to code in an EVAL.

my $answer = 42;
EVAL 'say $answer;';    # OUTPUT: «42␤» 

However, since the set of symbols in a lexical scope is immutable after compile time, an EVAL can never introduce symbols into the surrounding scope.

EVAL 'my $lives = 9'say $lives;   # error, $lives not declared 

Furthermore, the EVAL is evaluated in the current package:

module M {
    EVAL 'our $answer = 42'
}
say $M::answer;         # OUTPUT: «42␤» 

And also the current language, meaning any added syntax is available:

sub infix:<mean>(*@ais assoc<list> {
    @a.sum / @a.elems
}
EVAL 'say 2 mean 6 mean 4';     # OUTPUT: «4␤» 

An EVAL statement evaluates to the result of the last statement:

sub infix:<mean>(*@ais assoc<list> {
    @a.sum / @a.elems
}
say EVAL 'say 1; 2 mean 6 mean 4';         # OUTPUT: «1␤4␤» 

EVAL is also a gateway for executing code in other languages:

EVAL "use v5.20; say 'Hello from perl5!'":lang<Perl5>;

(Cool) sub EVALFILE

Defined as:

sub EVALFILE($filename where Blob|Cool:$lang = 'perl6')

Slurps the specified file and evaluates it. Behaves the same way as EVAL with regard to Blob decoding, scoping, and the $lang parameter. Evaluates to the value produced by the final statement in the file.

EVALFILE "foo.p6";

(Cool) routine unpolar

Defined as:

method unpolar(Real $angle)
multi sub unpolar(Real $magReal $angle)

Returns a Complex with the coordinates corresponding to the angle in radians and magnitude corresponding to the object value or $mag in the case it's being used as a sub

say 1.unpolar(⅓*pi);
# OUTPUT: «0.5000000000000001+0.8660254037844386i␤» 

(Cool) routine printf

Defined as:

method printf (*@args)
multi sub printf(Cool:D $format*@args)

As a method, takes the object as a format using the same language as Str.sprintf; as a sub, its first argument will be the format string, and the rest of the arguments will be substituted in the format following the format conventions.

"%s is %s".printf("þor""mighty");# OUTPUT: «þor is mighty» 
printf"%s is %s""þor""mighty"); # OUTPUT: «þor is mighty» 

(Cool) routine sprintf

Defined as:

method sprintf(*@args)
multi sub sprintf(Cool:D $format*@args)

Formats and outputs a string, following the the same language as Str.sprintf, using as such format either the object (if called in method form) or the first argument (if called as a routine)

sprintf"%s the %d%s""þor"1"st").put#OUTPUT: «þor the 1st␤» 
sprintf"%s is %s""þor""mighty").put;   # OUTPUT: «þor is mighty␤» 
"%s's weight is %.2f %s".sprintf"Mjölnir"3.3392"kg").put;
# OUTPUT: «Mjölnir's weight is 3.34 kg␤»