= Raku Types =

`raku(1)` has three essential data types, and they each feature a runtime type system.

<<TableOfContents>>

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== Scalars ==

A scalar is a single value. Scalars are named and referenced with a leading dollar sign (`$`).

{{{
my $a = 1;
}}}

Scalars can be any of strings (`Str`), integers (`Int`), or rational numbers (`Rat`).

Scalars can declared null, in which case they are typed as `Any`. If they are declared with any value, or if they are annotated with any type, they have the corresponding type.

{{{
my Int $a;
say $a.WHAT;   # (Int)

my $b;
say $b.WHAT;   # (Any)
$b= 1;
say $b.WHAT;   # (Int)
$b= "1";
say $b.WHAT;   # (Str)
$b= Nil;
say $b.WHAT;   # (Any)
}}}

If a scalar is annotated with a type and a mismatched value is assigned to it, a runtime error occurs.

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== Arrays ==

An array is a list of values. Arrays are named and referenced with a leading at sign (`@`). Array elements are indexed with integers starting at 0 surrounded by square brackets (`[`,`]`).

{{{
my @set = 'a','b','c';
@set[0] = 'd';
say @set;                # [d b c]
}}}

With string arrays, there are multiple options for declarations.

{{{
my @set = 'UK', 'Germany', 'France';
my @set = <UK Germany France>;                   # tokenized by whitespace
my @set = <<'United Kingdom' Germany France>>;   # tokenized while respecting quotes
}}}

Arrays can be declared with a fixed size.

{{{
my @set[3];
}}}

If an out-of-range index is assigned to, a runtime error occurs.

Arrays can also be declared as multi-dimensional.

{{{
my @table[3;2];
}}}

Arrays are typed according to the elements.

{{{
my Int @set = 1,2,3;
}}}

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== Hashes ==

A hash is a mapping of keys to values. Hashes are named and referenced with a leading percent sign (`%`). Hashes are index by keys surrounded by angled brackets (`<`,`>`).

These are equivalent declarations:

{{{
my %map = '1','001','2','002';
my %map = 1 => '001', 2 => '002';
say %map<1>;                        # 001
}}}

An empty hash can be declared in two ways:

{{{
my %map = {};
my %map = %();
}}}

Hashes are typed according to the values, not the keys.

{{{
my Int %map = '1',1,'2',2;
}}}

To constrain the type of keys as well, try:

{{{
my Int %map{Str} = '1',1,'2',2;
}}}

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== Enums ==

An enum is a mapping of names to values where the names themselves are the useful component.

{{{
enum Names ( John => 0, Jane => 1 );
enum Names ( :John(0), :Jane(1) );
enum Names <John Jane>;
}}}

Names are automatically stringified ''to their name'' as needed.

{{{
my $a = Names::John;
say $a;                # John
}}}

Many core data types are actually implemented as enums.

{{{
enum Bool <False True>;
enum Order (:Less(-1), :Same(0), :More(1));
enum Endian <NativeEndian LittleEndian BigEndian>;
}}}



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CategoryRicottone