(C++) Check if a std::string can be converted to an integer

include <iostream>

include <sstream>

include <cassert>


///Checks whether a std::string can be converted to an integer.
///Returns true if possible, also returning this integer by referencing.
///Returns false otherwise, setting the referenced integer to zero.
bool isInt(const std::string& s, int& rInt)
{
  std::istringstream i(s);
  if (!(i >> rInt))
  { 
    rInt = 0; 
    return false; 
  }
  return true;
}
int main()
{
  int value = 69;
  assert( isInt("IamNoInt", value) == false );
  assert( isInt("69", value) == true );
  if (isInt("123",value)==true)
  {
    std::cout << "The value is an integer" << std::endl;
    std::cout << "Its square is: " << value*value << std::endl;
  }
  else
  {
    std::cout << "The value is not integer" << std::endl;
  }
}

Other code snippets

(C++ Builder) Check if an AnsiString can be converted to an integer

Topic links

• iostream
• sstream
• assert
• cassert (Header file)
• string
• const
• cout