public/subjects/adding_twice/README.md

adding_twice

Instructions

In this exercise you will have to reuse your add_curry function (copy and paste it directly in your lib.rs file). Then you have to create the function twice using closures, this function will take a function f(x) as parameter and return a function f(f(x)). So, the purpose of this function is to add two times the value in add_curry to the original value.

Notions

• higher order function

Expected functions

The type of the arguments are missing. Use the example main function to determine the correct type.

pub fn twice<T>(F: _) -> _{

}

Usage

Here is a program to test your function.

use adding_twice::*;

fn main() {
    let add10 = add_curry(10);
    let value = twice(add10);
    println!("The value is {}", value(7));

    let add20 = add_curry(20);
    let value = twice(add20);
    println!("The value is {}", value(7));

    let add30 = add_curry(30);
    let value = twice(add30);
    println!("The value is {}", value(7));

    let neg = add_curry(-32);
    let value = twice(neg);
    println!("The value is {}", value(7));
}

And its output

$ cargo run
The value is 27
The value is 47
The value is 67
The value is -57
$