Arrays & Collections

Arrays, lists, and maps.

Achronyme has two built-in collection types: arrays (ordered lists) and maps (key-value dictionaries). Both are heap-allocated, mutable, and can hold any value type.

Arrays

Create arrays with square brackets. Access elements by index (zero-based).

let arr = [10, 20, 30]
assert(arr[0] == 10)
assert(arr[2] == 30)

let mixed = [1, "two", true, nil]
assert(mixed.len() == 4)

let nested = [[1, 2], [3, 4]]
assert(nested[0][1] == 2)

Mutate arrays with index assignment, .push(), and .pop():

mut nums = [0, 0, 0]
nums[0] = 10
assert(nums[0] == 10)

mut items = [1, 2]
items.push(3)
assert(items.len() == 3)

let last = items.pop()
assert(last == 3)
assert(items.len() == 2)

Array Methods

Method	Description
`.len()`	Number of elements
`.push(val)`	Append to end
`.pop()`	Remove and return last element
`.map(fn)`	Transform each element
`.filter(fn)`	Select elements matching predicate
`.reduce(init, fn)`	Fold into a single value
`.find(fn)`	First element matching predicate
`.any(fn)`	True if any element matches
`.all(fn)`	True if all elements match
`.sort(fn)`	Return sorted copy
`.flat_map(fn)`	Map and flatten one level
`.zip(other)`	Pair elements with another list
`.for_each(fn)`	Iterate for side effects

See Methods & Static Namespaces for the full reference.

Maps

Create maps with curly braces. Keys can be bare identifiers or quoted strings.

let person = {name: "Alice", age: 30}
assert(person.name == "Alice")
assert(person["age"] == 30)

let m = {"hello": 1, "world": 2}
assert(m["hello"] == 1)

Access values with dot notation or bracket notation. Bracket notation supports dynamic keys.

let key = "name"
assert(person[key] == "Alice")

let nested = {a: {b: {c: 42}}}
assert(nested.a.b.c == 42)

Add or update fields by assignment or with .set():

mut config = {}
config.debug = true
config["port"] = 8080
config.set("host", "localhost")
assert(config.len() == 3)

Map Methods

Method	Description
`.len()`	Number of key-value pairs
`.keys()`	List of all keys
`.values()`	List of all values
`.entries()`	List of `[key, value]` pairs
`.contains_key(key)`	Check if key exists
`.get(key, default)`	Get value with fallback
`.set(key, value)`	Add or update entry
`.remove(key)`	Remove and return value

See Methods & Static Namespaces for the full reference.

Iteration

Use for..in to iterate over arrays directly or over map keys with .keys().

mut total = 0
for x in [10, 20, 30] {
    total = total + x
}
assert(total == 60)

let scores = {math: 95, science: 88, english: 92}
mut sum = 0
for k in scores.keys() {
    sum = sum + scores[k]
}
assert(sum == 275)

Patterns

Dispatch table — store functions in a map for dynamic lookup:

let ops = {
    add: fn(a, b) { a + b },
    sub: fn(a, b) { a - b },
    mul: fn(a, b) { a * b }
}
assert(ops.add(10, 3) == 13)
assert(ops["mul"](4, 5) == 20)

Records — use maps as lightweight structs:

fn make_point(x, y) {
    return {x: x, y: y}
}
let p = make_point(3, 4)
assert(p.x == 3)

Word counting — dynamic keys for aggregation:

mut counts = {}
let words = ["apple", "banana", "apple", "cherry", "banana", "apple"]
for w in words {
    if counts[w] == nil {
        counts[w] = 0
    }
    counts[w] = counts[w] + 1
}
assert(counts.apple == 3)
assert(counts.banana == 2)

Functional pipelines — chain methods for data transforms:

let result = [1, 2, 3, 4, 5, 6]
    .filter(fn(n) { n % 2 == 0 })
    .map(fn(n) { n * 10 })
assert(result == [20, 40, 60])

Nested structures — arrays of maps, maps of arrays:

let people = [
    {name: "Alice", age: 30},
    {name: "Bob", age: 25}
]
assert(people[0].name == "Alice")

mut bag = {items: []}
bag.items.push("sword")
bag.items.push("shield")
assert(bag.items.len() == 2)