Function pointer

C++ :

#include <iostream>

using namespace std;

int eval(int (*f)(int, int), int x, int y) 
{
    return f(x,y);
}

int main()
{
    int a = 1;
    int b = 2;
    int c = eval([](int x, int y) { return x + y; }, a, b);
    cout << a << "+" << b << "=" << c << endl;
    return 0;
}

Rust :

fn eval(f: fn(i32,i32)->i32, x : i32, y : i32) -> i32    
{
    f(x, y)
}

fn main()
{
    let a = 1;
    let b = 2;
    let c = eval(|x,y| x+y, a, b);
    println!("{}+{}={}", a, b, c);
}