Structs

Structs are Vexel's primary mechanism for grouping related data together. They define a named type with a fixed set of typed fields.

Defining a Struct

Structs are declared with the struct keyword at the top level of a file. Each field is declared on its own indented line as name: type.

struct Vec2:
    x: float
    y: float

struct Entity:
    x: float
    y: float
    speed: float
    health: int
    name: str

Creating Instances

Instances are created with the new keyword followed by the struct name and positional arguments matching the field declaration order.

let pos: Vec2 = new Vec2(3.0, 4.0)

let player: Entity = new Entity(0.0, 0.0, 5.0, 100, "Hero")

Accessing Fields

Fields are read and written using dot notation.

let pos: Vec2 = new Vec2(3.0, 4.0)
print(pos.x)   # 3.0
print(pos.y)   # 4.0

# Mutate a field
let player: Entity = new Entity(0.0, 0.0, 5.0, 100, "Hero")
player.x = 10.0
player.health -= 25

Structs as Function Parameters

Structs are passed by value. When a struct is passed to a function, the function receives a copy. Modifying the copy does not affect the original.

fn length_sq(v: Vec2) -> float:
    return v.x * v.x + v.y * v.y

fn move_entity(e: Entity, dx: float, dy: float) -> Entity:
    # Return a new Entity with updated position
    return new Entity(e.x + dx, e.y + dy, e.speed, e.health, e.name)

fn main():
    let dir: Vec2 = new Vec2(3.0, 4.0)
    print(length_sq(dir))   # 25.0

    let p: Entity = new Entity(0.0, 0.0, 5.0, 100, "Hero")
    let moved: Entity = move_entity(p, 10.0, 5.0)
    print(moved.x)   # 10.0

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