Ada中类型/程序包别名的单独声明 [英] Separate declarations of types/packages aliases in Ada

问题描述

我想声明一些用户定义的编译器常量"，以使我的规范文件尽可能保持常量".这在C ++中很常见，例如:

I would like to declare some "user-defined compiler-constants" to keep my specification files as "constant" as possible. This is something common in C++, e.g. :

// misc/config.hh
namespace misc
{
  typedef std::shared_ptr<A> A_ptr; 
  namespace arch = ibmpc;
}

// misc/code.hh
#include "misc/config.hh"
namespace misc
{
  void function p(A_ptr a);
}

哪个人会在Ada里?

-- misc.ads
package Misc is
  use Types; ----> forbidden !

  procedure P(A : A_Access);
end Misc;

-- misc-types.ads
package Misc.Types is
  type A_Access is A'Access;
end Misc.Types;

这当然是行不通的，因为use是上下文关键字...因此，我的问题是:在Ada中如何做具有相同结果的事情?

Of course this does not work since use is a context keyword...hence my question : how is it possible to do something with the same results in Ada ?

推荐答案

我认为这是从C ++原始版本到Ada的合理映射:

I think this is a reasonable mapping from your C++ original to Ada:

首先，我认为文件misc.ads中与您的namespace misc相对应，

To start with, corresponding more-or-less, I think, to your namespace misc, in file misc.ads,

package Misc is
end Misc;

然后，与文件misc-config.ads中的config.hh相对应，

Then, corresponding to config.hh, in file misc-config.ads,

package Misc.Config is
   type A is (For_Example, An_Enumeration);
   type A_Access is access A;
end Misc.Config;

(当然，它也可以引用Misc中的类型).然后，对应于code.hh，在文件misc-code.ads中，

(which could, of course, also reference types in Misc). Then, corresponding to code.hh, in file misc-code.ads,

with Misc.Config;
package Misc.Code is
   use Config;
   procedure P (A : A_Access);
end Misc.Code;

就规范而言，个人而言我不会use Config;-这会使确定定义内容的位置变得困难.请注意，您可以在显示的位置说出use Config;或use Misc.Config;，因为您是Misc的孩子；在context子句中(也可以)，您必须use Misc.Config;.

Personally I wouldn’t use Config;, at any rate in specs - it can make it difficult to work out where something is defined. Note, you can say use Config; or use Misc.Config; where shown, because you’re in a child of Misc; in the context clause, which is also OK, you would have to use Misc.Config;.

这篇关于Ada中类型/程序包别名的单独声明的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！