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How to convert a string into a numeric type?

/ Published in: C++
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  1. #include <string>
  2. #include <sstream>
  3. #include <iostream>
  4.  
  5. template <class T>
  6. bool from_string(T& t, 
  7.                  const std::string& s, 
  8.                  std::ios_base& (*f)(std::ios_base&))
  9. {
  10.   std::istringstream iss(s);
  11.   return !(iss >> f >> t).fail();
  12. }
  13.  
  14. int main()
  15. {
  16.   int i;
  17.   float f;
  18.  
  19.   // the third parameter of from_string() should be 
  20.   // one of std::hex, std::dec or std::oct
  21.   if(from_string<int>(i, std::string("ff"), std::hex))
  22.   {
  23.     std::cout << i << std::endl;
  24.   }
  25.   else
  26.   {
  27.     std::cout << "from_string failed" << std::endl;
  28.   }
  29.  
  30.   if(from_string<float>(f, std::string("123.456"), std::dec))
  31.   {
  32.     std::cout << f << std::endl;
  33.   }
  34.   else
  35.   {
  36.     std::cout << "from_string failed" << std::endl;
  37.   }
  38.   return 0;
  39. }

URL: http://www.codeguru.com/forum/showthread.php?t=231054

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