編寫(xiě)一個(gè)貨幣兌換程序。具體來(lái)說(shuō)，是將歐元兌換成美元。

提示輸入手動(dòng)的歐元數(shù)，以及歐元的當(dāng)前匯率。打印可以兌換的美元數(shù)。

貨幣兌換的公式為：

image-20210628112823364.png

其中

• amountto 是美元
• amountfrom 是歐元數(shù)
• ratefrom 是歐元的當(dāng)前匯率
• rateto 是美元的當(dāng)前匯率

示例輸出

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.

約束

• 注意小數(shù)部分，不足1美分的向上取整。
• 使用單條輸出語(yǔ)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
    );
}
// 從控制臺(tái)讀取數(shù)據(jù)
fn read_from_console(notice: String) -> f32 {
    println!("{}", notice);
    loop {
        let mut amountfrom = String::new();
        // 控制臺(tái)輸入歐元金額
        std::io::stdin().read_line(&mut amountfrom).unwrap();
        // 注意要對(duì)輸入的字符串進(jìn)行trim()操作后再做類(lèi)型轉(zhuǎn)換
        if let Ok(res) = amountfrom.trim().parse::<f32>() {
            return res;
        } else {
            println!("輸入的數(shù)據(jù)類(lèi)型錯(cuò)誤：{}", amountfrom);
        }
    }
}

結(jié)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.