Function compose 

pub fn compose<A, B, C, F, G>(f: F, g: G) -> impl Fn(A) -> C
where
    F: Fn(B) -> C,
    G: Fn(A) -> B,

Composes two functions.

Takes two functions, f and g, and returns a new function that applies g to its argument, and then applies f to the result. This is equivalent to the mathematical composition f ∘ g.

Type Signature

forall a b c. (b -> c, a -> b) -> (a -> c)

Type Parameters

• A: The input type of the inner function g.
• B: The output type of g and the input type of f.
• C: The output type of the outer function f.
• F: The type of the outer function.
• G: The type of the inner function.

Parameters

• f: The outer function to apply second.
• g: The inner function to apply first.

Returns

A new function that takes an A and returns a C.

Examples

use fp_library::functions::compose;

let add_one = |x: i32| x + 1;
let times_two = |x: i32| x * 2;
let times_two_add_one = compose(add_one, times_two);

// 3 * 2 + 1 = 7
assert_eq!(
    times_two_add_one(3),
    7
);