The Perl6 type system

my $scalar;

our @array;

my %hash;

$scalar = “hi there”;

@array = 1, 2, “a string”;

%hash = one => 1, two => “2”;

my Any $scalar;

our Any @array;

my Any %hash;

$scalar = “hi there”;

@array = 1, 2, “a string”;

%hash = one => 1, two => “2”;

my Int $scalar;

our Int @array;

my Int %hash;

$scalar = “hi there”;

@array = 1, 2, “a string”;

%hash = one => 1, two => “2”;

my Int $scalar;

our Int @array;

my Int %hash;

$scalar = “hi there”;

@array = 1, 2, “a string”;

%hash = one => 1, two => “2”;

Type check failed in assignment to '$scalar'; expected 'Int' but got 'Str'

in block <unit> at types.pl:4

AST

Any

Array

Associative

Backtrace

Backtrace::Frame

Bag

BagHash

Baggy

Blob

Block

Bool

Buf

Callable

Capture

Channel

Code

Complex

Cool

CurrentThreadScheduler

Cursor

Date

DateTime

Dateish

Duration

Enum

EnumMap

Exception

Failure

FatRat

Grammar

Hash

IO

IO::Handle

IO::Pipe

IO::Socket

Instant

Int

Iterable

Iterator

Junction

Label

List

Lock

Macro

Match

Metamodel::C3MRO

Metamodel::ClassHOW

Metamodel::Finalization

Metamodel::Naming

Metamodel::Primitives

Method

Mix

MixHash

Mixy

Mu

Nil

Num

Numeric

ObjAt

Pair

PairMap

Parameter

Parcel

Pod::Block

Pod::Item

Positional

Proc

Proc::Async

Proc::Status

Promise

Proxy

QuantHash

Range

Rat

Rational

Real

Regex

Routine

Scheduler

Signature

Str

Thread

Version

Whatever

sub sum_0_to_n($n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

sub sum_0_to_n($n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3); 6

sub sum_0_to_n($n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(“3”);

6

sub sum_0_to_n($n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(“3”);

6

6

sub sum_0_to_n($n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(“3”);

say sum_0_to_n(“foo”);

6

6

sub sum_0_to_n($n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(“3”);

say sum_0_to_n(“foo”);

6

6

Cannot convert string to number:

base-10 number must begin with valid digits or '.' in '⏏foo' (indicated by ⏏)

In method Numeric at m-CORE:1576

In sub infix:<-> at m-CORE:5277

In sub infix:<-> at m-CORE:5277

In sub sub_0_to_n at sum.pl:3

In block <unit> at sum.pl:7

sub sum_0_to_n(Numeric $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(“foo”);

6

sub sum_0_to_n(Numeric $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(“foo”);

6

===SORRY!=== Error while compiling sum.pl

Calling 'sum_0_to_n' will never work with argument types (str)

Expected: :(Numeric $n)

at summer.pl:10

------> say ⏏sum_0_to_n("foo");

sub sum_0_to_n(Numeric $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

my $arg = “foo”;

say sum_0_to_n($arg);

6

sub sum_0_to_n(Numeric $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

my $arg = “foo”;

say sum_0_to_n($arg);

6

Type check failed in binding $n; expected 'Numeric' but got 'Str'

in sub sum_0_to_n at sum.pl:1

in block <unit> at sum.pl:8

sub sum_0_to_n(Numeric $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(3.5);

6

sub sum_0_to_n(Numeric $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(3.5);

6

Hangs… infinite loop

sub sum_0_to_n(Int $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(3.5);

6

sub sum_0_to_n(Int $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(3.5);

6

===SORRY!=== Error while compiling sum.pl

Calling 'sum_0_to_n' will never work with argument types (Rat)

Expected: :(Int $n)

at sum.pl:9

sub sum_0_to_n(Int $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(-3);

6

sub sum_0_to_n(Int $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(-3);

6

Hangs… Infinite loop

sub sum_0_to_n(Int $n where * >= 0) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(-3);

6

sub sum_0_to_n(Int $n where * >= 0) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(-3);

6

Constraint type check failed for parameter '$n'

in sub sum_0_to_n at sum.pl:4

in block <unit> at sum.pl:9

subtype NonNegInt of Int where * >= 0;

sub sum_0_to_n(NonNegInt $n) {

return 0 unless $n;

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(-3);

6

Constraint type check failed for parameter '$n'

in sub sum_0_to_n at sum.pl:4

in block <unit> at sum.pl:9

subtype NonNegInt of Int where * >= 0;

multi sub sum_0_to_n(0) { 0 }

multi sub sum_0_to_n(NonNegInt $n) {

return $n + sum_0_to_n($n – 1);

}

say sum_0_to_n(3);

say sum_0_to_n(-3);

6

Constraint type check failed for parameter '$n'

in sub sum_0_to_n at sum.pl:4

in block <unit> at sum.pl:9

subtype NonNegInt of Int where * >= 0;

multi sub sum_0_to_n(0) { 0 }

multi sub sum_0_to_n(NonNegInt $n) {

return $n + sum_0_to_n($n – 1);

}

multi sub sum_0_to_n(Int $n where * < 0) {

return $n + sum_0_to_n($n + 1);

}

say sum_0_to_n(3);

say sum_0_to_n(-3);

6

-6

subtype NonNegInt of Int where * >= 0;

multi sub sum_0_to_n(0) { 0 }

multi sub sum_0_to_n(NonNegInt $n) {

return $n + sum_0_to_n($n – 1);

}

multi sub sum_0_to_n(Int $n where * < 0) {

return $n + sum_0_to_n($n + 1);

}

sub MAIN(Int :$value!) {

say sum_0_to_n($value);

}

> perl6 sum.pl

Usage:

sum.pl –value=<Int>

subtype NonNegInt of Int where * >= 0;

multi sub sum_0_to_n(0) { 0 }

multi sub sum_0_to_n(NonNegInt $n) {

return $n + sum_0_to_n($n – 1);

}

multi sub sum_0_to_n(Int $n where * < 0) {

return $n + sum_0_to_n($n + 1);

}

sub MAIN(Int :$value!) {

say sum_0_to_n($value);

}

> perl6 sum.pl

Usage:

sum.pl –value=<Int>

> perl6 sum.pl –value=foo

Usage:

sum.pl --value=<Int>

subtype NonNegInt of Int where * >= 0;

multi sub sum_0_to_n(0) { 0 }

multi sub sum_0_to_n(NonNegInt $n) {

return $n + sum_0_to_n($n – 1);

}

multi sub sum_0_to_n(Int $n where * < 0) {

return $n + sum_0_to_n($n + 1);

}

sub MAIN(Int :$value!) {

say sum_0_to_n($value);

}

> perl6 sum.pl

Usage:

sum.pl –value=<Int>

> perl6 sum.pl –value=foo

Usage:

sum.pl –value=<Int>

> perl6 sum.pl – value=4

10

subtype NonNegInt of Int where * >= 0;

multi sub sum_0_to_n(0) returns Int { 0 }

multi sub sum_0_to_n(NonNegInt $n) returns Int {

return $n + sum_0_to_n($n – 1);

}

multi sub sum_0_to_n(Int $n where * < 0) returns Int {

return $n + sum_0_to_n($n + 1);

}

sub MAIN(Int :$value!) {

say sum_0_to_n($value);

}

class Dog {

has Str $.name;

has Int $.age is rw;

}

class Dog {

has Str $.name;

has Int $.age is rw;

}

class Owner {

has Str $.name;

has Dog @.dogs;

}

class Dog {

has Str $.name;

has Int $.age is rw;

}

class Owner {

has Str $.name;

has Dog @.dogs;

}

my $dog = Dog.new(name => 'Fido',

age => 'foo');

Type check failed in assignment to '$!age'; expected 'Int' but got 'Str'

in block at src/gen/m-CORE.setting:1009

in method BUILDALL at src/gen/m-CORE.setting:992

in method bless at src/gen/m-CORE.setting:981

in method new at src/gen/m-CORE.setting:967

in block <unit> at dogs.pl:10

class Dog {

has Str $.name;

has Int $.age is rw;

}

class Owner {

has Str $.name;

has Dog @.dogs;

}

my $dog = Dog.new(name => 'Fido',

age => '2');

$dog.age = “foo”;

Type check failed in assignment to '$!age'; expected 'Int' but got 'Str'

In block <unit> at dogs.pl:11

class Dog {

has Str $.name;

has Int $.age is rw;

}

class Owner {

has Str $.name;

has Dog @.dogs;

}

my $dog = Dog.new(name => 'Fido',

age =>2);

my $owner = Owner.new(name => 'Bob',

dogs => ($dog, 'foo'));

Type check failed in assignment to '@!dogs'; expected 'Dog' but got 'Str'

in method REIFY at src/gen/m-CORE.setting:10861

in method reify at src/gen/m-CORE.setting:9471

in method gimme at src/gen/m-CORE.setting:9954

in method sink at src/gen/m-CORE.setting:10438

in method BUILDALL at src/gen/m-CORE.setting:1083

in method bless at src/gen/m-CORE.setting:981

in method new at src/gen/m-CORE.setting:967

in block <unit> at dogs.pl:11

class Dog {

has Str $.name;

has Int $.age;

}

class Owner {

has Str $.name;

has Dog @.dogs;

}

my $dog = Dog.new(name => 'Fido',

age =>2);

my $owner = Owner.new(name => 'Bob',

dogs => ($dog));

If ($owner ~~ Dog) {

say “owner is-a Dog”;

} elsif ($owner ~~ Owner) {

say “owner is-a Owner”;

} else {

say “owner is-a something else”;

}

given $thing {

when Dog { say '$thing is-a Dog' }

when 3 { say '$thing is 3' }

when "blah" { say '$thing is blah' }

when /pattern/ { say '$thing matches /pattern/' }

when (10 .. 20) { say '$thing is between 10 and 20' }

when any(1, 4, 6) { say '$thing is 1, 4 or 6' }

}

class Dog {

has Str $.name;

has Int $.age;

}

class Owner {

has Str $.name;

has Dog @.dogs;

method ACCEPTS(Dog $d) {

return $d ~~ any(@.dogs);

}

}

class Dog {

has Str $.name;

has Int $.age;

}

class Owner {

has Str $.name;

has Dog @.dogs;

method ACCEPTS(Dog $d) {

return $d ~~ any(@.dogs);

}

}

my $fido = Dog.new(name => 'Fido', age => 3)

my $bob = Owner.new(name => 'Bob', dogs => ($fido));

my $fred = Owner.new(name => 'Fred');

given $fido {

When $fred { say “owned by Fred” }

When $bob { say “owned by Bob” }

}