如何编写将扩展为定义具有模板参数的对象的宏

Question

是否可以编写一个宏，进而从中创建一个对象定义，例如：

DEFINE_OBJECT_INVALID_VALUES(ObjectType, double, int, 1.0, 1)

应该变成：

ObjectType a<double, int>(1.0, 1);

和

DEFINE_OBJECT_INVALID_VALUES(ObjectType, double, int, bool, 1.0, 1, false)

应该变成：

ObjectType a<double, int, bool>(1.0, 1, false);

Answer 1

你可以overload a macro on number of arguments:

#define DEFINE_OBJECT_INVALID_VALUES_2(T1, V1)  \
        a<T1>(V1)
#define DEFINE_OBJECT_INVALID_VALUES_4(T1, T2, V1, V2)  \
        a<T1, T2>(V1, V2)
#define DEFINE_OBJECT_INVALID_VALUES_6(T1, T2, T3, V1, V2, V3)  \
        a<T1, T2, T3>(V1, V2, V3)
#define DEFINE_OBJECT_INVALID_VALUES_N(_1,_2,_3,_4,_5,_6,_7,_8,_9,N,...)  \
        DEFINE_OBJECT_INVALID_VALUES_##N
#define DEFINE_OBJECT_INVALID_VALUES(objecttype, ...)  \
        objecttype DEFINE_OBJECT_INVALID_VALUES_N(__VA_ARGS__,9,8,7,6,5,4,3,2,1)(__VA_ARGS__)

// will expand to:
// ObjectType a<double, int>(1.0, 1)
DEFINE_OBJECT_INVALID_VALUES(ObjectType, double, int, 1.0, 1) 

// will expand to:
// ObjectType a<double, int, bool>(1.0, 1, false)
DEFINE_OBJECT_INVALID_VALUES(ObjectType, double, int, bool, 1.0, 1, false)

如何编写将扩展为定义具有模板参数的对象的宏

How to write a macro that will be expanded to define an object with template parameters

c++

variadic-macros