May 12th Tuesday (五月 十二日 火曜日)

  The program dattrcol have more problem.  As to daily, monthly, yearly report the program dattrcol is not up to do.  Now we have
to study another program datrdcol.  Their program name is proximal.  But the program datrdcol is main used to make daily, monthly,
and yearly report.

  If a function call argument isn't an Lvalue or does not match the type of the corresponding const reference parameter,
C++ creates an anonymous variable of the correct type, assigns the value of the function call argument to the anonymous
variable, and has the parameter refer to that variable.

  You should declare formal reference arguments as const whenever it's appropriate to do so.

  Typically, the reference refers to a reference passed to the function in the first place, so the calling function actually
winds up directly accessing one of its own variables.

Remember

  A function that returns a reference is actually an alias for the referred-to variable.

  You can assign a value (including a structure or a class object) to a C++ function only if the function returns a reference
to a variable or, more generally, to a data object. In that case, the value is assigned to the referred-to variable or data object.

  There are two main reasons for using reference arguments:

  * To allow you to alter a data object in the calling function
  * To speed up a program by passing a reference instead of an entire data object

  The second reason is most important for larger data objects, such as structures and class objects.