2.10. Array

An array is a sequence of values indexed by an integer number from 0 to the size of the array minus 1. An array’s elements can be obtained by their index.

var a = [[int[4] 1; 2; 3; 4]] // fixed size of array is 4, and content is [1, 2, 3, 4]
assert(a[0] == 1)

var b: array<int>
push(b,1)
assert(b[0] == 1)

There are static arrays (of fixed size, allocated on the stack), and dynamic arrays (size is dynamic, allocated on the heap):

var a = [[int[4] 1; 2; 3; 4]] // fixed size of array is 4, and content is [1, 2, 3, 4]
var b: array<string>          // empty dynamic array
push(b, "some")               // now it is 1 element of "some"
b |> push("some")             // same as above line, but using pipe operator

Dynamic sub-arrays can be created out of any array type via range indexing:

var a  = [[int[4] 1; 2; 3; 4]]
let b <- a[1..3]               //  b is [{int 2;3}]

In reality a[b], where b is a range, is equivalent to subarray(a, b).

Resizing, insertion, and deletion of dynamic arrays and array elements is done through a set of standard functions (see built-in functions).

The relevant builtin functions are: push, push_clone, emplace, reserve, resize, erase, length, clear, and capacity.

Arrays (as well as tables, structures, and handled types) are passed to functions by reference only.

Arrays cannot be copied; only cloned or moved.

def clone_array(var a, b: array<string>)
  a := b      // a is not a deep copy of b
  clone(a, b) // same as above

def move_array(var a, b: array<string>)
  a <- b  // a is no points to same data as b, and b is empty.

Arrays can be constructed inline:

let arr = [[auto 1.; 2.; 3.; 4.5]]

This expands to:

let arr : float[4] = [[float[4] 1.; 2.; 3.; 4.5]]

Dynamic arrays can also be constructed inline:

let arr <- [{auto "one"; "two"; "three"}]

This is syntactic equivalent to:

let arr : array<string> <- to_array_move([[string[4] "one"; "two"; "three"]])

If only one element is specified, local data construction is of that element:

let i1 = [[int 1]]      // same is the line bellow
let i2 = 1

To create an array of an unspecified type, use [] syntax:

let ai1 <- [[int[] 1]]  // actually [[int[1] 1]]
let ai2 <- [[auto[] 1]  // same as above

When array elements can’t be copied, use push_clone to insert a clone of a value, or emplace to move it in.

resize can potentially create new array elements. Those elements are initialized with 0.

reserve is there for performance reasons. Generally, array capacity doubles, if exceeded. reserve allows you to specify the exact known capacity and significantly reduce the overhead of multiple push operations.

It’s possible to iterate over an array via a regular for loop:

for x in [[int[] 1;2;3;4]]
        print("x = {x}\n")

Additionally, a collection of unsafe iterators is provided:

def each ( a : auto(TT)[] ) : iterator<TT&>
def each ( a : array<auto(TT)> ) : iterator<TT&>

The reason both are unsafe operations is that they do not capture the array.

Search functions are available for both static and dynamic arrays:

def find_index ( arr : array<auto(TT)> implicit; key : TT )
def find_index ( arr : auto(TT)[] implicit; key : TT )
def find_index_if ( arr : array<auto(TT)> implicit; blk : block<(key:TT):bool> )
def find_index_if ( arr : auto(TT)[] implicit; blk : block<(key:TT):bool> )