Storage duration and mutability

Declaration semantics

Form	Allowed location	Reassignable	Purpose
var	Function/block	Yes	Ordinary mutable local variable
const	Top level	No	Global constant declaration
static	Top level	Yes	Static storage that exists for program lifetime

const PAGE_SIZE: i32 = 4096;
static request_count: i64 = 0;

fun main() {
    var limit: i32 = 4;
    var active: i32 = 0;
    var retries: i32 = 0;

    active += 1;
    retries += 1;
    println("{} {} {}", limit, active, retries);
}

Local variables

var value: i32 = 1;
value = 2;

var declares local storage, and its value can be reassigned. Use a top-level const for a named constant.

Local const and static

const and static are top-level declarations. They cannot be declared inside a function body or used as a for-loop initializer.

Lifetimes and pointers

You can take the address of a local with &, but ptr<T> does not track how long the referenced storage remains valid. If a local address escapes its scope, the surrounding program must ensure that the address is not used after the storage becomes invalid.