Rust每日练习---货币换算

编写一个货币兑换程序。具体来说，是将欧元兑换成美元。

提示输入手动的欧元数，以及欧元的当前汇率。打印可以兑换的美元数。

货币兑换的公式为：

image-20210628112823364.png

其中

• amountto 是美元
• amountfrom 是欧元数
• ratefrom 是欧元的当前汇率
• rateto 是美元的当前汇率

示例输出

How mang euros are you exchanging? 81

What is the exchange rate? 137.51

81 euros at an exchange rate of 137.51 is

111.38 U.S. dollars.

约束

• 注意小数部分，不足1美分的向上取整。
• 使用单条输出语句。

fn main(){
    let amountfrom = read_from_console(String::from("How mang euros are you exchanging?"));
    println!("euros is：{}", amountfrom);

    let ratefrom = read_from_console(String::from("What is the exchange rate?"));
    println!("exchange rate is：{}", ratefrom);

    const RATE_TO: f32 = 100.0;

    let result = (amountfrom * ratefrom).ceil() / RATE_TO;
    println!(
        "{} euros at an exchange rate of {} is {} U.S. dollars.",
        amountfrom, ratefrom, result
    );
}
// 从控制台读取数据
fn read_from_console(notice: String) -> f32 {
    println!("{}", notice);
    loop {
        let mut amountfrom = String::new();
        // 控制台输入欧元金额
        std::io::stdin().read_line(&mut amountfrom).unwrap();
        // 注意要对输入的字符串进行trim()操作后再做类型转换
        if let Ok(res) = amountfrom.trim().parse::<f32>() {
            return res;
        } else {
            println!("输入的数据类型错误：{}", amountfrom);
        }
    }
}

结果：

How mang euros are you exchanging?
81
euros is：81
What is the exchange rate?
137.51
exchange rate is：137.51
81 euros at an exchange rate of 137.51 is 111.39 U.S. dollars.