title: Hexagonal Number
signature: function hexagonal_number(n)
test_code: using Printf
  
  # SOLUTION CODE
  # ============================================
  PLACEHOLDER_CODE_BODY
  
  # TESTING CODE 
  # ============================================
  function validate_solution(actual, expected)
      return actual == expected
  end
  
  function driver(n, expected)
      try
  
          if validate_solution(PLACEHOLDER_FN_NAME(n), expected)
              return "PASSED";
          end
          return "FAILED";
      catch exception_obj
          return string(Base.typename(typeof(exception_obj)).wrapper);
      end
  end
  
  function main()
      
      result = driver(38, 2850);
      @printf("TEST-0...%s\n",result);
      
      result = driver(44, 3828);
      @printf("TEST-1...%s\n",result);
      
      result = driver(58, 6670);
      @printf("TEST-2...%s\n",result);
      
      result = driver(10, 190);
      @printf("TEST-3...%s\n",result);
      
      result = driver(31, 1891);
      @printf("TEST-4...%s\n",result);
      
      result = driver(53, 5565);
      @printf("TEST-5...%s\n",result);
      
      result = driver(94, 17578);
      @printf("TEST-6...%s\n",result);
      
      result = driver(64, 8128);
      @printf("TEST-7...%s\n",result);
      
      result = driver(71, 10011);
      @printf("TEST-8...%s\n",result);
      
      result = driver(59, 6903);
      @printf("TEST-9...%s\n",result);
      
  end
  
  main()
source_py: def hexagonal_number(n):
      return (n * ((2 * n) - 1))
source_cpp: int hexagonal_number(int n) {
    return n * ( 2 * n - 1 );
  }