Rust Brain Teasers/

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Puzzle 16: Explanation

Puzzle 16: Explanation

Let's learn how function overloading and variable overloading works in Rust.

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Test it out

Hit “Run” to see the code’s output.

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fn double_it(n: i32) -> i32 {
    n * 2
}
fn double_it(n: f32) -> f32 {
    n * 2.0
}
fn main() {
    println!("2 * 4 = {}", double_it(2));
}

Output

The program fails to compile, and we receive the following error message:

error[E0428]: the name "double_it" is defined multiple times

Explanation

In C++ and similar languages, redefining a function with different parameter types is known as function overloading. It allows us to provide similar functionality for multiple types without having to come up with a type-specific function name for each option. For example, the following is valid C++ code:

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#include <iostream>
using namespace std;
float double_it(float n) { 
    return n * 2.0;
}
int double_it(int n) { 
    return n * 2;
}
int main() {
  cout << double_it(2);
  return 0;
}

Function overloading works in C++ and not in Rust because of name mangling. When a function is compiled, a compiler-specific name for the function is created and used by the linker to connect function calls to actual memory addresses. In C++, mangled names include both the function name and the types ...