Data Types

Anvil supports both primitive and user-defined data types. Types are constructed using data type expressions.

Data Type Expressions

data-type-expression ::= ()
                       | logic
                       | $identifier
                       | ( $data-type-expression [ {digit}+ ] )

Meaning:

() represents the unit type.
logic is the single-bit type.
$identifier refers to a named type.
(T[n]) is an array of n elements of type T.

Examples:

logic
address_data_pair
logic[8]

Type Definitions

A named type can be introduced using a type definition:

data-type-definition ::= type $identifier [ $params ] = $data-type-expression ;

Example:

type byte = (logic[8]);
type word = (logic[32]);

Struct Definitions

A named struct type is defined as:

struct $identifier [ $params ] {
  $identifier : $data-type-expression
  { , $identifier : $data-type-expression }
}

Example:

struct address_data_pair {
  data : (logic[8]),
  addr : (logic[16])
}

Enum Definitions

An enum type is defined as:

enum $identifier {
  $identifier { , $identifier }
}

Example:

enum state {
  IDLE,
  BUSY,
  DONE
}