Exercise 1 gcd

simple gcd

cargo new gcd_1
cd gcd_1/src
# edit main.rst

fn gcd(mut m: u64, mut n: u64) -> u64 {
    assert!(m != 0 && n != 0);
    while m != 0 {
        if m < n {
            let t = m;
            m = n;
            n = t;
        }
        m = m % n;
    }
    n
}

fn main() {
    println!("gcd(6, 2) is {}", gcd(6, 2));
}

#[test]
fn test_gcd() {
    assert_eq!(gcd(2, 6), 2);
    assert_eq!(gcd(3, 5), 1);
}

cargo run prints:

   Compiling gcd_1 v0.1.0 (/Users/fangjun/open-source/notes/docs/source/rust/code/gcd_1)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.12s
     Running `target/debug/gcd_1`
gcd(6, 2) is 2

cargo test prints:

   Compiling gcd_1 v0.1.0 (/Users/fangjun/open-source/notes/docs/source/rust/code/gcd_1)
    Finished `test` profile [unoptimized + debuginfo] target(s) in 0.08s
     Running unittests src/main.rs (target/debug/deps/gcd_1-74f037a3d4552c7d)

running 1 test
test test_gcd ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

gcd from command line

cargo new gcd_2
cd gcd_2
cd gcd_2/src
# edit main.rs

use std::env;

fn gcd(mut m: u64, mut n: u64) -> u64 {
    assert!(m != 0 && n != 0);
    while m != 0 {
        if m < n {
            let t = m;
            m = n;
            n = t;
        }
        m = m % n;
    }
    n
}

fn main() {
    let args: Vec<String> = env::args().collect();
    if args.len() != 3 {
        eprintln!("Usage: {} <int1> <int2>", args[0]);
        std::process::exit(1);
    }

    // args[0] is the program name
    let num1: u64 = args[1]
        .parse()
        .expect("Please provide a valid integer for the first argument");

    let num2: u64 = args[2]
        .parse()
        .expect("Please provide a valid integer for the second argument");
    let n = gcd(num1, num2);

    println!("GCD of {} and {} is {}", num1, num2, n);
}

cargo run 5 15 prints:

   Compiling gcd_2 v0.1.0 (/Users/fangjun/open-source/notes/docs/source/rust/code/gcd_2)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.09s
     Running `target/debug/gcd_2 5 15`
GCD of 5 and 15 is 5