Arrays

Arrays are ordered, heterogeneous lists created with [...] literals.

let nums: int[] = [1, 2, 3, 4, 5]
let mixed = [1, "two", true, 3.14]
let empty: string[] = []

Indexing

Indexing is zero-based for reading and writing, and supports Python-style negative indices:

let first = nums[0]      // 1
let last  = nums[-1]     // 5
nums[0] = 99

len(nums) returns the element count. Newlines inside [...] are ignored, so literals may span multiple lines.

append

The append built-in returns a new array — reassign to keep the result:

let xs = [1, 2, 3]
xs = append(xs, 4)       // [1, 2, 3, 4]

Array methods

Arrays have a rich set of methods, called with dot syntax. Higher-order methods take an anonymous function fn(element, index).

Method	Description
`push(...items)`	Append items (mutates); returns new length
`pop()`	Remove and return the last element
`first()` / `last()`	First / last element
`slice(start, end)`	Sub-array `[start, end)`
`contains(v)` / `indexOf(v)`	Membership / first index (−1 if absent)
`join(sep)`	Join into a string
`reverse()` / `sort()`	Reverse / sort in place
`flatten()`	Flatten one level of nested arrays
`map(fn)`	Transform each element into a new array
`filter(fn)`	Keep elements where `fn` is truthy
`reduce(fn, init?)`	Fold to a single value
`forEach(fn)`	Run `fn` for each element
`find(fn)` / `findIndex(fn)`	First matching element / its index
`every(fn)` / `some(fn)`	All / any element passes `fn`

let nums = [1, 2, 3, 4, 5, 6]

let evenSquares = nums
    .filter(fn(n) { return n % 2 == 0 })
    .map(fn(n) { return n * n })

let total = nums.reduce(fn(acc, n) { return acc + n }, 0)

println(evenSquares.join(", "))   // "4, 16, 36"
println(total)                    // 21

For other structures — maps, sets, stacks, queues, heaps, tries — see the collections module.

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