Max and min values in a C++ enum

No, there is no way to find the maximum and minimum defined values of any enum in C++. When this kind of information is needed, it is often good practice to define a Last and First value. For example,

enum MyPretendEnum
{
   Apples,
   Oranges,
   Pears,
   Bananas,
   First = Apples,
   Last = Bananas
};

There do not need to be named values for every value between First and Last.

No. An enum in C or C++ is simply a list of constants. There is no higher structure that would hold such information.

Usually when I need this kind of information I include in the enum a max and min value something like this:

enum {
  eAaa = 1,
  eBbb,
  eCccc,
  eMin = eAaaa,
  eMax = eCccc
}

See this web page for some examples of how this can be useful: Stupid Enum Tricks

  enum My_enum
    {
       FIRST_VALUE = 0,

       MY_VALUE1,
       MY_VALUE2,
       ...
       MY_VALUEN,

       LAST_VALUE
    };

after definition, My_enum::LAST_VALUE== N+1

No, not in standard C++. You could do it manually:

enum Name
{
   val0,
   val1,
   val2,
   num_values
};

num_values will contain the number of values in the enum.