你可以让一个递增的编译器常数？ [英] Can you make an incrementing compiler constant?

问题描述

虽然听起来荒谬的......

While sounding nonsensical.....

我要一个常量，每一个使用它时它会递增1

I want a Constant where every time you use it it will increment by 1

int x;
int y;
x = INCREMENTING_CONSTANT;
y = INCREMENTING_CONSTANT;

其中x == 1;和y == 2

where x == 1; and y == 2

请注意，我不想Y = INCREMENTING_CONSTANT + 1型的解决方案。

Note I don't want y = INCREMENTING_CONSTANT+1 type solutions.

基本上我想使用它作为一个编译时唯一的ID（通常它不会在code类的例子，但另一个宏内部使用）

Basically I want to use it as a compile time unique ID ( generally it wouldn't be used in code like the example but inside another macro)

推荐答案

您可能能够使用Boost装上去在一起。preprocessor（用C厂）和 BOOST_PP_COUNTER

You may be able to put something together using Boost.Preprocessor (Works with C) and BOOST_PP_COUNTER

页面上给出的示例：

#include <boost/preprocessor/slot/counter.hpp>   
BOOST_PP_COUNTER // 0

#include BOOST_PP_UPDATE_COUNTER()   
BOOST_PP_COUNTER // 1

#include BOOST_PP_UPDATE_COUNTER()  
BOOST_PP_COUNTER // 2

#include BOOST_PP_UPDATE_COUNTER()
BOOST_PP_COUNTER // 3

翻译成你想要的东西。

Translated into what you want

#include <boost/preprocessor/slot/counter.hpp> 

int x = BOOST_PP_COUNTER; // 0

#include BOOST_PP_UPDATE_COUNTER()   
int y = BOOST_PP_COUNTER;// 1

#include BOOST_PP_UPDATE_COUNTER()  
int z = BOOST_PP_COUNTER; // 2

您也可以使用插槽（以更code的成本比上述​​方案更灵活一点）：

You could also use slots (slightly more flexible at the cost of more code than the above solution):

#include <boost/preprocessor/slot/slot.hpp>

#define BOOST_PP_VALUE 0 //ensure 0 to start
#include BOOST_PP_ASSIGN_SLOT(1) 
int a = BOOST_PP_SLOT(1); //0

#define BOOST_PP_VALUE 1 + BOOST_PP_SLOT(1)
#include BOOST_PP_ASSIGN_SLOT(1) 
int b = BOOST_PP_SLOT(1); //1

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