Simple calculator in Rust

calculator.rs

use std::str::FromStr;

use regex::Regex;

const ADDITION: &str = "(\\d+)\\s*?(\\+)\\s*?(\\d+)";
const SUBTRACTION: &str = "(\\d+)\\s*?(\\-)\\s*?(\\d+)";
const MULTIPLICATION: &str = "(\\d+)\\s*?(\\*)\\s*?(\\d+)";
const DIVISION: &str = "(\\d+)\\s*?(/)\\s*?(\\d+)";

fn main() {
    // Traer datos del usuario
    println!("Por favor introduce tu expresión: ");
    let mut expression = String::new();
    std::io::stdin().read_line(&mut expression).unwrap();

    expression = perform_operation(expression, MULTIPLICATION);
    expression = perform_operation(expression, DIVISION);
    expression = perform_operation(expression, ADDITION);
    expression = perform_operation(expression, SUBTRACTION);

    // Mostrar el resultado
    println!("El resultado es: {}", expression);
}

fn perform_operation(mut expression: String, operation: &str) -> String {
    let operation_regex = Regex::from_str(operation).unwrap();

    loop {
        let caps = operation_regex.captures(expression.as_str());

        if caps.is_none() {
            break;
        }

        let caps = caps.unwrap();

        let cap_expression = caps.get(0).unwrap().as_str();
        let left_value: i32 = caps.get(1).unwrap().as_str().parse().unwrap();
        let operation: &str = caps.get(2).unwrap().as_str();
        let right_value: i32 = caps.get(3).unwrap().as_str().parse().unwrap();

        let result = match operation {
            "+" => left_value + right_value,
            "-" => left_value - right_value,
            "*" => left_value * right_value,
            "/" => left_value / right_value,
            _ => 0,
        };

        expression = expression.replace(cap_expression, &result.to_string());
    }
    expression
}