如何将VCL用作单独的命名空间?

huangapple go评论73阅读模式
英文:

How to use VCL as a separate namespace?

问题

我的目标是将所有vectorclass库的类型名称分离到一个单独的命名空间中,以便vcl::Vec4i会编译,但Vec4i不会。我尝试使用手册中的示例,但它不起作用。

失败的尝试按照手册

#include <iostream>
#include "vcl/vectorclass.h"
#define VCL_NAMESPACE vcl
using namespace vcl; //error
int main() {
 vcl::Vec4i vec; //error
 Vec4i vec; //仍然可以编译
 return 0;
}

失败信息:

root@vlad:/avx_vcl clang++ -std=c++17 -mavx -o test main.cpp 
main.cpp:4:17: error: expected namespace name
using namespace vcl;
                ^
main.cpp:6:2: error: use of undeclared identifier 'vcl'
        vcl::Vec4i vec;
        ^
2 errors generated.

期望的结果:

#define VCL_NAMESPACE vcl
int main() {
 vcl::Vec4i vec; //编译
 Vec4i vec; //不会编译
 return 0;
}

我应该更改什么?

英文:

My goal is to separate all vectorclass-library typenames to a separate namespace, so that vcl::Vec4i will compile, but Vec4i won't. I tried to use example from manual, however it's not working.

Failed attempt following the manual:

#include &lt;iostream&gt;
#include &quot;vcl/vectorclass.h&quot;
#define VCL_NAMESPACE vcl
using namespace vcl; //error
int main() {
 vcl::Vec4i vec; //error
 Vec4i vec; //still compiles
 return 0;
}

Failure message:

root@vlad:/avx_vcl clang++ -std=c++17 -mavx -o test main.cpp 
main.cpp:4:17: error: expected namespace name
using namespace vcl;
                ^
main.cpp:6:2: error: use of undeclared identifier &#39;vcl&#39;
        vcl::Vec4i vec;
        ^
2 errors generated.

Desired result:

#define VCL_NAMESPACE vcl
int main() {
 vcl::Vec4i vec; //compiles
 Vec4i vec; //won&#39;t compile
 return 0;
}

What should I change?

答案1

得分: 2

如章节 2.7 使用命名空间 中所指出的,您需要在包含任何 vcl 标头之前,直接或间接地定义 VCL_NAMESPACE,因此将顺序更改为:

#define VCL_NAMESPACE vcl
#include "vcl/vectorclass.h"   // 这行在 #define 之后
using namespace vcl;           // ...现在这将起作用

如果我们查看定义 Vec4ivectori128.h 文件,我们会发现该文件中的所有定义都被 #ifdef VCL_NAMESPACE 对包围:

#ifdef VCL_NAMESPACE
namespace VCL_NAMESPACE {
#endif
// 所有的定义,包括 Vec4i
#ifdef VCL_NAMESPACE
}
#endif

所以,如果在包含任何这些标头之前 定义 VCL_NAMESPACE,它将 将它们放入您选择的命名空间中。

注意 - 您需要在包含任何 vcl 标头的 所有 文件中首先放置此 #define VCL_NAMESPACE vcl。最简单的方式可能是告诉编译器始终定义它。g++ 示例:

g++ -DVCL_NAMESPACE=vcl ...
英文:

As noted in chapter 2.7 Using a namespace, you need to define VCL_NAMESPACE before including any vcl headers, directly or indirectly, so change the order to:

#define VCL_NAMESPACE vcl
#include &quot;vcl/vectorclass.h&quot;   // this line after the #define
using namespace vcl;           // ...and now this will work

If we look inside vectori128.h which defines Vec4i we see that all of the definitions in the file are surrounded by an #ifdef VCL_NAMESPACE pair:

#ifdef VCL_NAMESPACE
namespace VCL_NAMESPACE {
#endif
// all the definitions, including Vec4i
#ifdef VCL_NAMESPACE
}
#endif

So, what happens is that if you don't define VCL_NAMESPACE before including any of those headers, it will not put them in the namespace you've selected.

Note - You need to put this #define VCL_NAMESPACE vcl first in all your files that include any vcl header, directly or indirectly. It may be easiest to give the compiler the instruction to just define it always. g++ example:

g++ -DVCL_NAMESPACE=vcl ...

huangapple
  • 本文由 发表于 2023年6月15日 02:53:23
  • 转载请务必保留本文链接:https://go.coder-hub.com/76476731.html
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定