字符串分数加倍

Question

我需要一个函数来解析用户输入的数字到双精度数.我无法做任何客户端或改变输入的方式.

Input       | Desired Output
"9"         | 9
"9 3/4"     | 9.75
" 9  1/ 2 " | 9.5
"9 .25"     | 9.25
"9,000 1/3" | 9000.33
"1/4"       | .25

我看过这篇文章,但它使用了Python,我只是想知道在我花时间编写自己的文章之前是否有人知道任何花哨的C#处理方法.

Answer 1

我会使用正则表达式:

Regex re = new Regex(@"^\s*(\d+)(\s*\.(\d*)|\s+(\d+)\s*/\s*(\d+))?\s*$");
string str = " 9  1/ 2 ";
Match m = re.Match(str);
double val = m.Groups[1].Success ? double.Parse(m.Groups[1].Value) : 0.0;

if(m.Groups[3].Success) {
    val += double.Parse("0." + m.Groups[3].Value);
} else {
    val += double.Parse(m.Groups[4].Value) / double.Parse(m.Groups[5].Value);
}

尚未经过测试,但我认为它应该有效.

这是一个演示,这是另一个演示.

Answer 2

这是我最终使用的：

private double ParseDoubleFromString(string num)
{
    //removes multiple spces between characters, cammas, and leading/trailing whitespace
    num = Regex.Replace(num.Replace(",", ""), @"\s+", " ").Trim();
    double d = 0;
    int whole = 0;
    double numerator;
    double denominator;

    //is there a fraction?
    if (num.Contains("/"))
    {
        //is there a space?
        if (num.Contains(" "))
        {
            //seperate the integer and fraction
            int firstspace = num.IndexOf(" ");
            string fraction = num.Substring(firstspace, num.Length - firstspace);
            //set the integer
            whole = int.Parse(num.Substring(0, firstspace));
            //set the numerator and denominator
            numerator = double.Parse(fraction.Split("/".ToCharArray())[0]);
            denominator = double.Parse(fraction.Split("/".ToCharArray())[1]);
        }
        else
        {
            //set the numerator and denominator
            numerator = double.Parse(num.Split("/".ToCharArray())[0]);
            denominator = double.Parse(num.Split("/".ToCharArray())[1]);
        }

        //is it a valid fraction?
        if (denominator != 0)
        {
            d = whole + (numerator / denominator);
        }
    }
    else
    {
        //parse the whole thing
        d = double.Parse(num.Replace(" ", ""));
    }

    return d;
}