How to find string value in exponential format in C #?

Question

I want to find if a string has an exponential format or not. I am currently checking as shown below.

var s = "1.23E+04";
var hasExponential = s.Contains("E");

But I know that this is not so. So can anyone be guided in the right and fast way to achieve my requirement?

Answer 1

If you also want to make sure that it is indeed a number, and not just a string with an “E” in it, perhaps such a function may be useful. The logic remains simple.

private bool IsExponentialFormat(string str)
{
    double dummy;
    return (str.Contains("E") || str.Contains("e")) && double.TryParse(str, out dummy);
}

Answer 2

Try using regex?

string s = "1.23E+04";
string pattern = @"^\d{1}.\d+(E\+)\d+$";
Regex rgx = new Regex(pattern, RegexOptions.IgnoreCase);
bool hasExponential = rgx.IsMatch(s);

Answer 3

e. double.TryParse. . ( , ParseExponential2 , ParseExponential1 .)

public static void _Main(string[] args)
{
    string[] exponentials = new string[] { "1.23E+4", "1.23E+04", "1.23e+4", "1.23", "1.23e+4e+4", "abce+def", "1.23E-04" };

    for (int i = 0; i < exponentials.Length; i++)
        Console.WriteLine("Input: {0}; Result 1: {1}; Result 2: {2}; Result 3: {3}", exponentials[i], (ParseExponential1(exponentials[i]) ?? 0), (ParseExponential2(exponentials[i]) ?? 0), (ParseExponential3(exponentials[i]) ?? 0));
}

public static double? ParseExponential1(string input)
{
    if (input.Contains("e") || input.Contains("E"))
    {
        string[] inputSplit = input.Split(new char[] { 'e', 'E' });

        if (inputSplit.Length == 2) // If there were not two elements split out, it an invalid exponential.
        {
            double left = 0;
            int right = 0;

            if (double.TryParse(inputSplit[0], out left) && int.TryParse(inputSplit[1], out right) // Parse the values
                && (left >= -5.0d && left <= 5.0d && right >= -324) // Check that the values are within the range of a double, this is the minimum.
                && (left >= -1.7d && left <= 1.7d && right <= 308)) // Check that the values are within the range of a double, this is the maximum.
            {
                double result = 0;

                if (double.TryParse(input, out result))
                    return result;
            }
        }
    }

    return null;
}

public static double? ParseExponential2(string input)
{
    if (input.Contains("e") || input.Contains("E"))
    {
        double result = 0;

        if (double.TryParse(input, out result))
            return result;
    }

    return null;
}

public static double? ParseExponential3(string input)
{
    double result = 0;

    if (double.TryParse(input, out result))
        return result;

    return null;
}

ParseExponential1, ParseExponential2 ParseExponential3 null, . .

ParseExponential3 , , . (I.e., 1.23 1.23.)

double. .

, , , Regex nevermoi 500ms 100 000 exponentials, ParseExponential1 547ms ParseExponential2 317ms. sstan 346ms. , ParseExponential3 134ms.

string[] exponentials = new string[] { "1.23E+4", "1.23E+04", "1.23e+4", "1.23", "1.23e+4e+4", "abce+def", "1.23E-04" };

Stopwatch sw = new Stopwatch();
sw.Start();
for (int round = 0; round < 100000; round++)
    for (int i = 0; i < exponentials.Length; i++)
        ParseExponential1(exponentials[i]);
sw.Stop();
Console.WriteLine("Benchmark 1 (ParseExponential1) complete: {0}ms", sw.ElapsedMilliseconds);

sw.Reset();

sw.Start();
for (int round = 0; round < 100000; round++)
    for (int i = 0; i < exponentials.Length; i++)
        ParseExponential2(exponentials[i]);
sw.Stop();
Console.WriteLine("Benchmark 2 (ParseExponential2) complete: {0}ms", sw.ElapsedMilliseconds);
sw.Reset();
string pattern = @"^\d{1}.\d+(E\+)\d+$";
Regex rgx = new Regex(pattern, RegexOptions.IgnoreCase);

sw.Start();
for (int round = 0; round < 100000; round++)
    for (int i = 0; i < exponentials.Length; i++)
        rgx.IsMatch(exponentials[i]);
sw.Stop();
Console.WriteLine("Benchmark 3 (Regex Parse) complete: {0}ms", sw.ElapsedMilliseconds);
sw.Reset();

sw.Start();
for (int round = 0; round < 100000; round++)
    for (int i = 0; i < exponentials.Length; i++)
        IsExponentialFormat(exponentials[i]);
sw.Stop();
Console.WriteLine("Benchmark 4 (IsExponentialFormat) complete: {0}ms", sw.ElapsedMilliseconds);

sw.Start();
for (int round = 0; round < 100000; round++)
    for (int i = 0; i < exponentials.Length; i++)
        ParseExponential3(exponentials[i]);
sw.Stop();
Console.WriteLine("Benchmark 5 (ParseExponential3) complete: {0}ms", sw.ElapsedMilliseconds);

:

private static bool IsExponentialFormat(string str)
{
    double dummy;
    return (str.Contains("E") || str.Contains("e")) && double.TryParse(str, out dummy);
}