-   
- #include <iostream> 
- #include <string> 
- #include <sstream> 
-   
- int main() { 
-   
- 	using namespace std; 
-   
- 	std::istringstream iss("0"); 
- 	double d; 
-   
- 	if (iss >> d) 
- 	{ 
- 		cout << "number: " << d << endl; 
- 	} else { 
- 		cout << "NaN: " << d << endl; 
- 	} 
-   
- } 
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