Ada字符串文字常量数组 [英] Ada constant array of string literals

问题描述

我有大量的C语言，希望进入我的ada项目。该数组用于存储资产的文件名，这些文件将在以后加载。看起来像这样：

I have a large array in C that I wish to move into my ada project. That array is used to store filenames for assets which will later be loaded. It looks something like:

const char *filenames[NUMBER_OF_FILES] = {
    /* file[0] */ "res/0.file",
    /* ... */
    /* file[n] */ "res/some_more/complicated/file.name"
};

我想将其移动到ada程序包中，但找不到合适的方法它。显然，我的第一个尝试是：

I want to move this into an ada package body, but can't find a decent way to do it. Obviously my first attempt was:

filenames : constant array (File_Index) of String := (
    index_0 => "res/0.file",
    --  ...
    index_n => "res/some_more/complicated/file.name"
);

但是String当然是不受限制的类型，所以Ada不允许这样做。我将其切换为使用Unbounded_Strings，该方法有效，但非常难看（必须使用 To_Unbounded_String 包装每个字符串。

But of course String is an unconstrained type, so Ada won't allow that. I switched it to use Unbounded_Strings, which worked, but was very ugly (having to wrap each string with To_Unbounded_String.

是否有任何方法可以生成无约束类型的数组，其大小将在编译时就这样知道，还是我必须使用无界字符串？

Is there any way to make an array of unconstrained types whose size will be known at compile time like this, or do I have to use unbounded strings?

推荐答案

有点低级且重复，但是也许您可以创建一个小程序（甚至在Ada中也可以）以生成类似

It’s a bit low-level and repetitive, but perhaps you can create a little program (maybe even in Ada!) to generate something like

with Ada.Text_IO; use Ada.Text_IO;
procedure Lambdabeta is
   F1 : aliased constant String := "res/0.file";
   F2 : aliased constant String := "res/some_more/complicated/file.name";
   type Strings is array (Positive range <>) of access constant String;
   Filenames : constant Strings := (F1'Access,
                                    F2'Access);
begin
   for J in Filenames'Range loop
      Put_Line (Filenames (J).all);
   end loop;
end Lambdabeta;

另请参见此答案关于最大程度地减少使用 To_Unbounded_String 的痛苦。

See also this answer on minimising the pain of using To_Unbounded_String.

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