Luma documentation
Collections
Lists ([1, 2, 3])

Lists ([1, 2, 3])

Luma supports lists as a core data structure, offering both mutability and simplicity, along with a rich set of methods inspired by modern programming languages.

Declaration 

nums: [int] = [1, 2, 3]
words: [str] = ["hello", "world"]

Access & Walk

Index Access

print(nums[0])         // prints: 1

Safe Access

val: ?int = nums.get(0)    // returns 1
val = nums.get(10)         // returns nil

Safe Access

val: ?int = nums.get(0)    // returns 1
val = nums.get(10)         // returns nil

Walk a List

nums.walk(index, value) -> {
    print("${index}: ${value}")
}

nums.walk(value) -> print(value)

Core Methods

Operation Syntax Returns
Get Length nums.len() Number of elements
Get by Index nums.get(1) / nums[1] Optional value (?T)
Find Index of Value nums.index_of(3) Optional index (?int)
Add Value nums.add(4) Mutates the list
Remove by Value nums.remove(2) Returns true or false
Remove by Index nums.remove_at(1) Removes element at index
Intersect nums.intersect([1, 3]) New list with common values

Immutable Alternatives

For functional-style workflows:

Operation Syntax Returns
Add nums + [4] New list
Remove nums - [2] New list

Advanced Features

Feature Syntax / Method Returns
Slicing nums[0…2] [1, 2, 3]
Bulk Add nums.add_all([4, 5]) Mutates list
Bulk Remove nums.remove_all([1, 2]) Mutates list
Sort nums.sort() Sorts in place
Filter nums.filter(x -> x > 1) New filtered list

Design Principles

  • Intuitive Syntax: Square brackets, slicing, and dot methods are easy to learn.
  • Safe by Default: .get() and .index_of() return nil instead of crashing.
  • Consistent: All methods use snake_case.
  • Mutable + Immutable: Choose your preferred style.
  • Performant: Mutations are optimized internally.

Equality

  • [1, 2] == [1, 2] → true
  • [1, 2] == [2, 1] → false (order matters)
  • Sort before comparing if needed:
sorted1 = list1.sort()
sorted2 = list2.sort()
print(sorted1 == sorted2)

Examples 

nums: [int] = [1, 2]
nums.add(3)                    // [1, 2, 3]  
nums.remove(2)                 // true
found: ?int = nums.get(1)      // 3

// Immutable style
new_nums = nums + [4]          // [1, 3, 4]
filtered = new_nums.filter(x -> x > 1)  // [3, 4]

// Advanced
slice = nums[0..1]             // [1]
nums.sort()                    // [1, 3]
common = nums.intersect([3])  // [3]

Edge Cases

Case Behavior
.get(99) Returns nil
.index_of(“xyz”) Returns nil
.remove(“x”) Returns false
.intersect([]) Returns empty list
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Maps ({"a": 1})