How do I call a seperate struct, and import it into another impl trait for a struct?

Question

I know the title sounds weird, but basically I am creating a mathematics library in Rust. I have 1 Struct that has Basic functions like Differentiation, Newton's Method, Series, etc. but I also have numerical Integration Algorithms. The issue I have is that I want to call my Integration Algorithms through crate_name::Functions::Integration::<name_of_function> but I haven't figured out a way. I really don't know where to start when it comes to find a solution to this and that why I came here.

This is my src/ directory for reference:

src/
...lib.rs
...func/
......mod.rs
......functions.rs
......integration.rs

if you need it here is the github for the directory in question: https://github.com/VLambda/NumeriLib/tree/main/src/func

mod.rs:

mod functions;
mod integration;
pub use functions::*;

functions.rs:

use crate::func::integration::Integration;

pub struct Functions;

impl Functions {
pub fn right_riemann<F: Fn(f64) -> f64>(
        function: F,
        lower_limit: f64,
        upper_limit: f64,
        intervals: f64,
    ) -> f64 {
        Integration::right_riemann(function, lower_limit, upper_limit, intervals)
    }
}

integration.rs:

pub struct Integration;

impl Integration {
...
}

So far I've made it so that you would need to call the functions for Integration via crate_name::Functions::<name_of_function> but I think it would be better if I can call it through crate_name::Functions::Integration::<name_of_function>. Is this doable with my current code, or do I need to drastically change the project structure to accommodate this?

Answer 1

Rust isn't Java. In Rust you don't need to create an empty struct just to hold free functions, you can (and should) simply put the free functions directly in a module:

pub mod functions {
    pub mod integration {
        pub fn riemann() { todo!(); }
    }
}

Then you can call the function with just functions::integration::riemann()

And of course you can split the modules into individual files if you want to:

/// src/lib.rs
pub mod functions;

// src/functions.rs
pub mod integration;

// src/functions/integration.rs
pub fn riemann() { todo!(); }