错误信息

cppFunction('
  // adds x and y, but only if they are positive
  int add_positive_numbers(int x, int y) {
      // if x is negative, stop
      if(___) stop("x is negative") ;
    
      // if y is negative, stop
      if(___) ___("y is negative") ;
     
      return x + y ;
  }
')

# Call the function with positive numbers
add_positive_numbers(2, 3)

# Call the function with a negative number
add_positive_numbers(-2, 3)