Functions

Basics

fn add(a: i32, b: i32): i32 {
    return a + b
}

fn greet(name: string): void {
    print("hello, ", name)
}

Generic functions

fn identity<T>(x: T): T {
    return x
}

let n = identity(42)       // T inferred as i32
let s = identity("hello")  // T inferred as string

Built-in functions

Function	Description
print(args...)	Print with trailing newline
exit(code)	Exit the process
jsonStringify(val)	Serialize a struct to JSON
embedFile(path)	Embed file contents at compile time

Reference parameters

Functions can borrow values with &T (immutable) or &mut T (mutable):

fn length(s: &string): i64 {
    return s.len
}

fn double(x: &mut i32) {
    x = x * 2
}

var n: i32 = 21
double(n)          // n is now 42

Milo auto-borrows at call sites — you write double(n) not double(&n).

See Ownership for why references are restricted to function parameters.

Next: Structs →