c# - String Fraction to Double

Question

I need a function to parse a user inputs of numbers to doubles. I cannot do anything client side or change how the input comes in.

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

I saw this post, but it uses Python, I was just wondering if anybody knew any fancy C# ways of handling this before I spend time to write my own.

Answer 1

I would use regular expressions for this one:

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);
}

Untested, as of yet, but I think it should work.

Here's a demo, and here's another demo.