text: #include <fir.hpp>
  
  int main()
  {
  	// Copy on write fluent interface.
  	fir::parse_result<int> choice = fir::console::read_line()
  		.trim()
  		.parse_int()
  		.between(0, 3);
  
  	// Implicilty convertible to bool. 
  	if (choice)
  	{
  		fir::console::write_line("You selected %i!", *choice);
  	}
  }
  