Variables

Declaration

Variables are declared with their type, name, and an optional initializer:

i32 x = 10;
i64 big = 9999999;
i8* message = "hello";

Immutability by Default

All variables are immutable by default. Attempting to reassign will produce a compile error:

i32 x = 10;
x = 20;  // Error: cannot reassign immutable variable

Mutable Variables

Use the mut keyword after the variable name to allow reassignment:

i32 mut counter = 0;
counter = counter + 1;  // OK

Mutable parameters use mut before the type:

void increment(mut i32 x) {
    x = x + 1;
}

Type Inference

Use auto to let the compiler infer the type from the initializer:

auto x = 42;           // inferred as i32
auto p = Point(1, 2);  // inferred as Point

auto works with mut:

auto mut result = 0;
result = compute();

Compile-Time Constants

Use constexpr to declare variables evaluated entirely at compile time:

constexpr i32 MAX_SIZE = 1024;
constexpr i32 BUFFER = 4 * MAX_SIZE;

constexpr variables support arithmetic, comparison, logic, and references to other constants. They can be used anywhere a constant is expected, including fixed-size array lengths:

constexpr i32 SIZE = 64;
i8* buf = i8[SIZE];  // stack-allocated array of 64 bytes

See Compile-Time Evaluation for full details on constexpr and consteval.

Scope

Variables are block-scoped. Inner blocks can shadow outer variables:

i32 main() {
    i32 x = 10;
    {
        i32 x = 20;  // shadows outer x
    }
    return x;  // 10
}