Question

正是标题所要求的。我正在浏览一些Ada代码并遇到了

SELECT
        Id_P ,
        Monthindex     ,
        (
                SELECT
                        100 * (STDEV(ResEligible.num_valid) / AVG(ResEligible.num_valid)) AS Pre_Coef_Var
                FROM
                        tbl_p a CROSS APPLY
                        (
                                SELECT
                                        e.Monthindex ,
                                        e.num AS num_valid
                                FROM
                                        dbo.tbl_p e
                                WHERE
                                        e.Monthindex     = a.MonthIndex
                                AND     e.Id_P = a.Id_P

                                UNION ALL

                                SELECT DISTINCT
                                        B1.[MonthIndex       ] ,
                                        Tr.num AS num_valid
                                FROM
                                        #tbl_pr B1
                                INNER JOIN
                                        #tbl_pr B2
                                ON
                                        B1.[Id_P] = B2.[Id_P]
                                AND     B2.Rang - B1.Rang BETWEEN 0 AND     2
                                INNER JOIN
                                        dbo.tbl_p Tr
                                ON
                                        Tr.Id_P = B1.Id_P
                                AND     Tr.Monthindex     = B1.Monthindex
                                WHERE
                                        a.Id_P = B1.[Id_P]
                                AND     B2.[MonthIndex]  =
                                        (
                                                SELECT
                                                        MAX([MonthIndex])
                                                FROM
                                                        #tbl_pr
                                                WHERE
                                                        [MonthIndex]     < a.MonthIndex
                                                AND     [Id_P] = a.Id_P) ) AS ResEligible
                WHERE
                        a.Id_P = result.Id_P
                AND     a.MonthIndex     = result.MonthIndex) AS Coeff
FROM
        tbl_p AS result
WHERE
        1          = 1
AND     MonthIndex = @CurrentMonth
GROUP BY
        Id_P ,
        Monthindex) AS CC

是什么意思？像C ++模板参数一样吗？

Answer 1

Ada中的通用名称是package，procedure或function，具有一个或多个形式参数。形式参数可以是对象，类型，包或子程序。实例化泛型时，必须为所有形式参数提供实际值。

generic
   type X is (<>); -- formal parameter
procedure Foo(Item : in X);

在此声明中，Foo是泛型，X是形式参数。 (<>)意味着实例化Foo时，X的实际值必须是离散类型（有符号整数类型，模数类型或枚举类型）：

procedure Bar is new Foo(Character);

Bar现在是通用过程Foo的实例，可以用类型Character的参数调用：

Bar('@');

泛型类型X是（<>）;意思？

1 个答案: