Determining if a string is a double

Question

I would like to see if a string contains a double as its sole contents. In other words, if it could possibly be the output of the following function:

string          


        

Answer 1

You can use the Boost lexical_cast to check whether a string contains double or not.

#include  
....
using boost::lexical_cast; 
using boost::bad_lexical_cast; 
....
template bool isValid(const string& num) { 
   bool flag = true; 
   try { 
      T tmp = lexical_cast(num); 
   } 
   catch (bad_lexical_cast &e) { 
      flag = false; 
   } 
   return flag; 
} 

int main(){
  // ....
 if (isValid(str))
     cout << "valid double." << endl; 
 else 
     cout << "NOT a valid double." << endl;
  //....
}