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In the last couple of days, I've created variations of a simple algorithm to demonstrate how Celcius and Fahrenheit seem to relate to each other if you "mirror the number".
It wasn't supposed to be about the programming language. Still, I used Python in the first one and I noticed that since the code is simple, it could be fun to write variants of it in other languages.

1. Converting Celsius to Fahrenheit with Python
2. Converting Celsius to Fahrenheit with TypeScript
3. Converting Celsius to Fahrenheit with Go
4. Converting Celsius to Fahrenheit with Ruby
5. Converting Celsius to Fahrenheit with Crystal
6. Converting Celsius to Fahrenheit with Rust

It was a fun exercise.

And speaking of fun, I couldn't help but to throw in a benchmark using hyperfine that measures, essentially, how fast these CLIs can start up. The results look like this:

Summary
  ./conversion-rs ran
    1.31 ± 1.30 times faster than ./conversion-go
    1.88 ± 1.33 times faster than ./conversion-cr
    7.15 ± 4.64 times faster than bun run conversion.ts
   14.27 ± 9.48 times faster than python3.12 conversion.py
   18.10 ± 12.35 times faster than node conversion.js
   67.75 ± 43.80 times faster than ruby conversion.rb

It doesn't prove much, that you didn't expect. But it's fun to see how fast Python 3.12 has become at starting up.

Head on over to https://github.com/peterbe/temperature-conversion to play along. Perhaps you can see some easy optimizations (speed and style).

Previously in this series:

1. Converting Celsius to Fahrenheit with Python
2. TypeScript
3. Go
4. Ruby
5. Crystal

This time, in Rust:

fn c2f(c: i8) -> f32 {
    let c = c as f32;
    c * 9.0 / 5.0 + 32.0
}

fn is_mirror(a: i8, b: i8) -> bool {
    let a = massage(a);
    let b = reverse_string(massage(b));
    a == b
}

fn massage(n: i8) -> String {
    if n < 10 {
        return format!("0{}", n);
    } else if n >= 100 {
        return massage(n - 100);
    } else {
        return format!("{}", n);
    }
}

fn reverse_string(s: String) -> String {
    s.chars().rev().collect()
}

fn print_conversion(c: i8, f: i8) {
    println!("{}°C ~= {}°F", c, f);
}

fn main() {
    let mut c = 4;
    while c < 100 {
        let f = c2f(c);
        if is_mirror(c, f.ceil() as i8) {
            print_conversion(c, f.ceil() as i8)
        } else if is_mirror(c, f.floor() as i8) {
            print_conversion(c, f.floor() as i8)
        } else {
            break;
        }
        c += 12;
    }
}

Run it like this:

rustc -o conversion-rs conversion.rs && ./conversion-rs

and the output becomes:

4°C ~= 40°F
16°C ~= 61°F
28°C ~= 82°F
40°C ~= 104°F
52°C ~= 125°F