Array Types

The array type is a list of elements of a single type.

Signature

<array_signature> ::= ["packed"] "[" <type_signature> ";" <expr> "]" ;

Dependencies:

The <array_signature> consists of an optional "packed" keyword prefix to a type signature and expression separated by a colon, delimited by brackets.

Instantiation

<array_instantiation> ::= [<data_location>] "[" <expr> ("," <expr>)* [","] "]" ;

Dependencies:

The <array_instantiation> is an optional data location annotation followed by a comma separated list of expressions delimited by brackets.

Element Access

<array_element_access> ::= <ident> "[" <expr> [":" <expr>] "]" ;

Dependencies:

The <array_element_access> is the array's identifier followed a bracket-delimited expression and optionally a second expression, colon separated.

Examples

type TwoElementIntegerArray = [u8; 2];
type TwoElementPackedIntegerArray = packed [u8; 2];

const arr: TwoElementIntegerArray = [1, 2];

const elem: u8 = arr[0];

Instantiation of a fixed-length array stores one element per 32 byte word in either data location. The only difference between data locations in terms of instantiation behavior is if all elements of the array are populated with constant values and the array belongs in memory, a performance optimization may include code-copying an instance of the constant array from the bytecode into memory.

Access

Array element access depends on whether the second expression is included. If a single expression is inside the access brackets, the single element is returned from the array. If a second expression follows the first with a colon in between, a pointer of the same data location is returned. The type of the new array pointer is the same type but the size is now the size of the second expression's value minus the first expression's value. If the index values are known at compile time and are greater than or equal to the array's length, a compiler error is thrown, else a bounds check against the array's length is added into the runtime bytecode.