Rust SIG

cargo.toml

[package]
name = "webservice"
version = "0.1.0"
authors = ["Mario Martinez <zenitram.oiram@gmail.com>"]
edition = "2018"

[dependencies]
rocket = "0.4.0"
perfect_numbers = { path = "../perfect-numbers" }

notes.md

Rust SIG notes

Intro

What is Rust? My short description is that it's a better C or C++. And it's better in the sense that it's safer and has learned a lot from programming languges that have come before it.

We see Rust everywhere. Where can we use it?

• Terminal programs
• Embedded software
• Gaming
• IoT
• Web Development
• Any computationally intensive tasks

Not so good for:

• Rapid prototying
• Machine learning

How to install

You could use brew install rust but better to use rustup.rs

rustup is like rvm or nvm but can do so much omre

Today

• Solve a simple problem
• Wrap it in a web service

Perfect Numbers

This is a problem for exercism.io

Simple problem but the Option type might take some getting used to.

Explain cargo when running tests.

Version 1

With if/else

Version 2

With ordering - show $ rustup docs

Web Service

$ cargo new webservice

Start with this and install rocket as it takes time.

While installing, discuss:

• Several web framework for rust - actix web, tower, warp, serverless
• Talk through source code

perfect-number-ver1.rs

use std::cmp::Ordering;

#[derive(Debug, PartialEq, Eq)]
pub enum Classification {
    Abundant,
    Perfect,
    Deficient,
}

pub fn classify(num: u64) -> Option<Classification> {
    if num == 0 {
        return None;
    };

    let aliquot_sum: u64 = (1..=(num / 2))
        .filter(|potential_factor| num % potential_factor == 0)
        .sum();

    Some(match aliquot_sum.cmp(&num) {
        Ordering::Equal => Classification::Perfect,
        Ordering::Greater => Classification::Abundant,
        Ordering::Less => Classification::Deficient,
    })
}

perfect-number-ver2.rs

use std::cmp::Ordering;

#[derive(Debug, PartialEq, Eq)]
pub enum Classification {
    Abundant,
    Perfect,
    Deficient,
}

pub fn classify(num: u64) -> Option<Classification> {
    match num {
        0 => None,
        _ => Some({
            let aliquot_sum: u64 = (1..=(num / 2)).filter(|n| num % n == 0).sum();
            match aliquot_sum.cmp(&num) {
                Ordering::Equal => Classification::Perfect,
                Ordering::Greater => Classification::Abundant,
                Ordering::Less => Classification::Deficient,
            }
        }),
    }
}

web-service-with-option-handles.rs

#![feature(proc_macro_hygiene, decl_macro)]

#[macro_use]
extern crate rocket;

extern crate perfect_numbers;
use perfect_numbers::Classification::{Abundant, Deficient, Perfect};

#[get("/")]
fn index() -> &'static str {
    "Hello, world!"
}

#[get("/perfect-number/<number>")]
fn perfect_number(number: u64) -> Option<&'static str> {
    perfect_numbers::classify(number).map(|classification| match classification {
        Perfect => "Perfect",
        Abundant => "Abundant",
        Deficient => "Deficient",
    })
}

fn main() {
    rocket::ignite()
        .mount("/", routes![index, perfect_number])
        .launch();
}

web-service-with-unwrap.rs

#![feature(proc_macro_hygiene, decl_macro)]

#[macro_use]
extern crate rocket;
extern crate perfect_numbers;

#[get("/")]
fn index() -> &'static str {
    "Hello, world!"
}
#[get("/perfect-number/<number>")]
fn perfect_number(number: u64) -> &'static str {
    perfect_numbers::classify(number)
        .map(|classification| match classification {
            perfect_numbers::Classification::Perfect => "Perfect",
            perfect_numbers::Classification::Abundant => "Abundant",
            perfect_numbers::Classification::Deficient => "Deficient",
        })
        .unwrap()
}

fn main() {
    rocket::ignite()
        .mount("/", routes![index, perfect_number])
        .launch();
}