Variables & Constants

In SP, variables can be declared using type inference (let and var) or explicit type annotations.

1import std.io;
2
3fn main() -> void {
4    // 1. Immutable bindings with 'let' (recommended)
5    let language = "SP";
6    let version = 1.0;
7    
8    // 2. Mutable bindings with 'var'
9    var counter = 0;
10    counter = counter + 1;
11    
12    // 3. Explicit type annotations
13    int explicitAge = 25;
14    string explicitCity = "Stockholm";
15    
16    println("${language} v${version} - Count: ${counter}");
17}

Immutability by Default with `let`

Variables declared with let are immutable once initialized. Reassigning a let variable triggers a compile-time error:

Mutability with `var`

When a value needs to be reassigned, declare it with var. The type of the variable is inferred from the initial assignment and cannot change to an incompatible type.