Double or Integer in string?

Question

For example in a console application I have the following code:

Console.Writeline("Enter function");
string function = Console.Readline();

and then function gets defined as:

function = "ceil(5.0)";

then I would define the variable as a double. But what if the user would enter:

function = "ceil(5)";

How can I do a check if there is a double filled in or an integer so I now how to store that variable. And also if its the same but then with negative numbers, I already tried regex but maybe I didn't do it right. Any ideas?

Modify the code parsing the function entered by the user to detect the presence of a decimal point? Surely, if you are able to write a function parser, that should be piece of cake for you? — Heinzi, Apr 26 '16 at 07:43
@Heinzi Thanks i will look into that, but then if there is for example 5.0 its recognized as a double but it actually is an integer if you know what i mean — Jurriaan Buitenweg, Apr 26 '16 at 07:47
I know what you mean, but I would recommend to *still* use a double in that case: That's what most programming languages do if you use a literal such as `5.0`, and it would be confusing to change that convention. — Heinzi, Apr 26 '16 at 07:55

score 3 · Accepted Answer · edited May 23 '17 at 12:32

3

For floating point numbers, n % 1 == 0 is typically the way to check if there is anything past the decimal point.

public static void Main (string[] args)
{
    decimal d = 3.1M;
    Console.WriteLine((d % 1) == 0);
    d = 3.0M;
    Console.WriteLine((d % 1) == 0);
}

Output:

False //is a double
True //is a integer

More information can be found at this page: How to determine if a decimal/double is an integer?

edited May 23 '17 at 12:32

Community

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answered Apr 26 '16 at 07:40

Robin Dirksen

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I think the asker wants it the other way, check if string contains double or integer. You are checking if a double is a whole number or contains decimals. – RvdK Apr 26 '16 at 07:43

score 0 · Answer 2 · edited Sep 20 '16 at 12:12

0

If you want to do it using Regex, you could check for function+parenthesis+value+closing_parenthesis. Check this as a starting point:

ceil\((\-?\d{1,}(?:.\d{1,})?)\)

Please note that Regex allows negative numbers. If you don't want that, remove the \-? part.

edited Sep 20 '16 at 12:12

The One and Only ChemistryBlob

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answered Apr 26 '16 at 08:56

Cleptus

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Double or Integer in string?

2 Answers2