Data Structures

Arrays and Tensors

Literals:

[1, 2, 3, 4, 5]
[3.14, 2.71, 1.41]
[[1, 2], [3, 4]]          # 2D

Array fill syntax:

[3 4 ; 0]
# 3×4 array filled with 0: [[0,0,0,0], [0,0,0,0], [0,0,0,0]]

Indexing (bracket must be adjacent, no space):

let arr = [10, 20, 30, 40] in arr[2]    # 30
let m = [[1, 2, 3], [4, 5, 6]] in m[1, 2]  # 6

With a space, f [1,2] is function application (passing [1,2] to f), not indexing.

Operations:

len [1, 2, 3, 4]              # 4
shape [[1, 2], [3, 4]]        # [2, 2]
reverse [1, 2, 3]             # [3, 2, 1]

⟨1, 2⟩                        # Unicode
(1, 2)                        # ASCII
⟨3.14, 2.71, 1.41⟩
⟨⊤, 5, "hello"⟩               # Heterogeneous

Access by index:

let pair = ⟨10, 20⟩ in pair.0    # 10
let triple = ⟨1, 2, 3⟩ in triple.2  # 3

Destructuring:

let (x, y) = ⟨5, 10⟩ in x + y    # 15

Named fields in tuple-like syntax:

⟨x: 10, y: 20⟩
⟨name: "Alice", age: 30, active: ⊤⟩

Field access:

let point = ⟨x: 5.0, y: 10.0⟩ in point.x    # 5.0

Greek letters in field names:

let stats = ⟨μ: 10.0, σ: 2.0, σ²: 4.0, n: 100⟩ in stats.σ²
# Result: 4.0

⟨Left 5⟩
⟨Right "error"⟩
⟨Some 42⟩
⟨None⟩

Pattern matching on variants:

match ⟨Some 42⟩
  ⟨None⟩ → 0
  ⟨Some x⟩ → x
# Result: 42

Enum declarations:

enum Option α where Some α | None
enum Either α β where Left α | Right β