src/bin/tut3.rs

// Generic Programming: Static Polymorphism

#![allow(dead_code)]
#![allow(unused_imports)]

use rust_tutorial::*;

/// Run this to see the disassembly of `compute_sum_of_squares_{1,2}`:
///
/// ```bash
/// cargo objdump --bin tut3 --release -- -d | awk -v RS= '/^([[:xdigit:]]+ )?tut3::compute_sum_of_squares/'
/// ```

#[inline(never)]
fn compute_sum_of_squares_i32(zero: i32, xs: &Vec<i32>) -> i32 {
    xs[1..].iter()
        .map(|x| x * x)
        .fold(zero, |acc, x| acc + x)
}

#[inline(never)]
fn compute_sum_of_squares<T>(zero: T, xs: &Vec<T>) -> T
where
    T: std::ops::Mul<Output=T> + std::ops::Add<Output=T> + Copy
{
    xs[1..].iter()
        .map(|x| *x * *x)
        .fold(zero, |acc, x| acc + x)
}

fn main() {
    let numbers = vec![1, 2, 3, 4, 5];

    let sum_of_squares_i32 = compute_sum_of_squares_i32(0, &numbers);
    let sum_of_squares_t   = compute_sum_of_squares(0, &numbers);

    println!("sum i32 = {}", sum_of_squares_i32);
    println!("sum T   = {}", sum_of_squares_t);
}