Generics

Generic Functions

fn max<T>(a: T, b: T) -> T {
    if a > b { return a }
    return b
}

var bigger = max(10, 20)        // 20
var larger = max(3.14, 2.71)    // 3.14

Generic Structs

Structs with type parameters:

struct Pair<T> {
    first: T
    second: T
}

var p = Pair { first: 10, second: 20 }
println(p.first.to_string())   // 10
println(p.second.to_string())  // 20

// Field access and expressions
var sum = p.first + p.second    // 30

Mixed generic and concrete fields:

struct Box<T> {
    value: T
    label: string
}

var b = Box { value: 42, label: "answer" }
println(b.label)  // answer

Built-in Generic Types

// Result<T> — success or error
fn safe_div(a: int, b: int) -> Result<int> {
    if b == 0 { return Err("division by zero") }
    return Ok(a / b)
}

// Option<T> — present or absent
fn find(arr: [int], target: int) -> Option<int> {
    for i in 0..arr.len() {
        if arr[i] == target { return Some(i) }
    }
    return None
}

See Also

• Functions — generic function syntax
• Structs — generic struct types
• Traits — constrain generic types