compiler-errors - 使用软件包时出错

Question

我有以下程序:

with Ada.Text_IO;
with pkg_task;
with pkg_procedure;

procedure exercise2 is
    my_task : task_t;
begin
    loop
        my_task.ConsultsState;
    end loop;
end;

使用以下软件包 pkg_task:

with Text_IO;

package body pkg_task is
    task body task_t is
        entry IsEven(N: Integer) is
            EvenConsult : Integer := 0;
            OddConsult : Integer := 0;
        begin
            if N rem 2 = 0 then
                Put_Line("Number " & N & " is even");
                EvenConsult := EvenConsult + 1;
            else
                Put_Line("Number " & N & " is odd");
                OddConsult := OddConsult + 1;
            end if;
        end IsEven;

        entry ConsultsState is
        begin
            Put_Line("Total even numbers consulted: " & EvenConsult);
            Put_Line("Total odd numbers consulted: " & OddConsult);
        end ConsultsState;
    end task_t;
end pkg_task;

编译时出现以下错误:

gcc-4.9 -c exercise2.adb
exercise2.adb:6:19: "task_t" is not visible
exercise2.adb:6:19: non-visible declaration at pkg_task.ads:2
exercise2.adb:9:17: invalid prefix in selected component "my_task"
gnatmake: "exercise2.adb" compilation error

我不知道该如何解决。

Answer 1

这是范围和可见性之间的区别。
with pkg_task;表示此pkg_task现在在您的范围内，但其元素不直接可见。

因此，为了使用task_t，您可以为它加上包名称pkg_task.task_t作为前缀，或者使用use子句(use pkg_task;)使类型可见。

有关此主题的更多信息，您可以检查Ada Distilled。