Variables

Variables in Zeus are statically typed and must be declared with explicit type annotations.

Declaration

Use the let keyword to declare mutable variables:

let age: i32 = 25;
let temperature: f64 = 98.6;
let isActive: boolean = true;

Use const for immutable values:

const PI: f64 = 3.14159;
const MAX_SIZE: i32 = 100;

Type Annotations

Every variable requires a type annotation:

let name: string = "Zeus";
let count: i32 = 42;
let ratio: f64 = 0.5;
let flag: boolean = false;

The syntax is: let variableName: Type = value;

Default Values

Variables can be declared without an initial value. They receive type-appropriate defaults:

function main(): i32 {
  let x: i32;      // Defaults to 0
  let y: f64;      // Defaults to 0.0
  let b: boolean;  // Defaults to false

  return x;  // Returns 0
}

Type	Default Value
`i8`, `i16`, `i32`, `i64`	`0`
`u8`, `u16`, `u32`, `u64`	`0`
`f32`, `f64`	`0.0`
`boolean`	`false`
Object types	`null`

Reassignment

Variables declared with let can be reassigned:

let counter: i32 = 0;
counter = 1;
counter = counter + 1;  // counter is now 2

Naming Conventions

Variable names must:

Start with a letter or underscore
Contain only letters, digits, and underscores
Not be a reserved keyword

// Valid names
let userName: i32 = 1;
let _private: i32 = 2;
let count2: i32 = 3;

// Invalid names
// let 2count: i32 = 4;   // Cannot start with digit
// let my-var: i32 = 5;   // Hyphens not allowed
// let let: i32 = 6;      // Reserved keyword

Scope

Variables are scoped to the block they’re declared in:

function main(): i32 {
  let outer: i32 = 10;

  if (outer > 5) {
    let inner: i32 = 20;
    // Both outer and inner are accessible here
  }

  // Only outer is accessible here
  // inner is out of scope

  return outer;
}

Object Variables

When declaring object variables, you must use the class name as the type:

class Point {
  public x: i32;
  public y: i32;
}

function main(): i32 {
  let p: Point = new Point();
  p.x = 10;
  p.y = 20;

  return p.x + p.y;
}

Object variables can be assigned null:

let p: Point = null;

Types →