how do I check if input from cin is a double? [duplicate]

This question already has answers here: Closed 12 years ago.

Possible Duplicates:

How to validate numeric input C++

how do I validate user input as a double in C++?

I need to get input from the command line and check if it is a valid number... storing it as a double. If the input is invalid, I need to keep asking for a number.

double x;
cout << '>';
cin >> x;


while (/*x is invalid*/){
 cout << "Invalid Input! Please input 开发者_如何学编程a number." << endl;
 cout << '>';
 cin >> x;
}

So how do I check if it is valid?

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parse the string and check if there are numbers and 0 or one dot. If these rules aren't met, you just print an error message.

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See "How to validate numeric input in C++" - already asked and answered on the site.