如何检查一个元素是否属于一种子类型或另一种子类型？

Question

我刚刚了解了 Ada 中的枚举和类型，并决定编写一个小程序来练习：

with Ada.Text_IO;                       use Ada.Text_IO;
with Ada.Integer_Text_IO;       use Ada.Integer_Text_IO;

procedure Day is 

    type Day_Of_The_Week is (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday);

    subtype Weekday is Day_Of_The_Week range Monday..Friday;

    subtype Weekend is Day_Of_The_Week range Saturday..Sunday;

        function is_Weekday ( dayOfTheWeek: in Day_Of_The_Week) return Boolean is
        begin
            if(--?--)
        end is_Weekday;

    selected_day_value  :   Integer;
    selected_day                :   Day_Of_The_Week;

begin
    Put_Line("Enter the number co-responding to the desired day of the week:");
    Put_Line("0 - Monday");
    Put_Line("1 - Tuesday");
    Put_Line("2 - Wednesday");
    Put_Line("3 - Thursday");
    Put_Line("4 - Friday");
    Put_Line("5 - Saturday");
    Put_Line("6 - Sunday");
    Get(selected_day_value);
    selected_day = Day_Of_The_Week'pos(selected_day_value);

    if( is_Weekday(selected_day))
        Put_Line( Day_Of_The_Week'Image(selected_day) & " is a weekday." );
    else
        Put_Line( Day_Of_The_Week'Image(selected_day) & " is a weekday." );

end Day;

我在 if 语句方面遇到了麻烦。如何检查 dayOfTheWeek 是否属于工作日子类型或周末子类型？

Answer 1

另外，您希望

function is_Weekday ( dayOfTheWeek: in Day_Of_The_Week) return Boolean is
begin
    return dayoFTheWeek in Weekday;
end is_Weekday;

输入 'Val 而不是 'Pos

selected_day := Day_Of_The_Week'val(selected_day_value);

，并且您可以查看第二个 Put_Line 中的单词！

Answer 2

您不需要一个函数来检查这一点。在这种情况下，函数只会掩盖发生的事情：

if Selected_Day in Weekday then
  do stuff..
else
  do other stuff...
end if;