Types 如何检查元素是否属于一个子类型？

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;

我对if语句有问题。如何检查DayOfWeek是否在Weekday子类型或weekend子类型中？

是否需要

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

另外，您希望

'Val

而不是

'Pos

处于

selected_day := Day_Of_The_Week'val(selected_day_value);

---

你可以看看第二行的单词

您不需要函数来检查这一点。在这种情况下，函数只会掩盖发生的情况：

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

---

只是一个书呆子，但您的代码假定输入有效。IRL您应该在枚举上使用表示子句来保证范围为0-6，并获取一个整数，使用未经检查的整数类型转换，检查它是否有效，然后检查周末/工作日子类型。为什么不显式输入一周中的

天

<代码>包周中的日文本IO是新的Ada.Text IO.Enumeration IO（周中的日）然后<编码>获取（所选天数）；跳绳