Monomorphization

In programming languages, monomorphization is a compile-time process where polymorphic functions are replaced by many monomorphic functions for each unique instantiation.^[1] This transformation is desirable, since then the output intermediate representation (IR) will have concrete types and can be optimized better. Furthermore, most IRs are designed to be low-level and do not support polymorphism. Code generated this way is typically faster than boxed types, but may compile slower and take more space due to duplicating the function body.^{[2][3][4][5][6][7]}

Example[]

For example, this is an example of a use of a generic identity function

fn id<T>(x: T) -> T {
    return x;
}

fn main() {
    let int = id(10);
    let string = id("some text");
    println!("{0}, {1}", int, string);
}

After monomorphization, this would become

fn id_i32(x: i32) -> i32 {
    return x;
}

fn id_str(x: &str) -> &str {
    return x;
}

fn main() {
    let int = id_i32(10);
    let string = id_str("some text");
    println!("{0}, {1}", int, string);
}

See also[]

• Parametric polymorphism
• Type erasure
• Template (C++)

References[]