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c++variadic-macrosboost-preprocessor

Can we implement a max or min macro, which can take variable arguments (more than two parameters )

I want to implement a new max/min macro, which can take more than two parameter, for example:

#define max( ... ) ...

and then, I can use it like this:

max( p0, p1, p2, p3 )
max( 2, 4, 100 )
max( 1,2,3,4,5,6,7 ) -> 7

if this macro can help us to implement that macro?

#define PP_EXPAND(X) X
#define PP_ARG_COUNT(...) PP_EXPAND(PP_ARG_POPER(__VA_ARGS__, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0))
#define PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16, N, ...) N

#define PP_ARG_AT(Index, ...) PP_ARG_AT_##Index(__VA_ARGS__)
#define PP_ARG_AT_0(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16, __VA_ARGS__))
#define PP_ARG_AT_1(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, __VA_ARGS__))
#define PP_ARG_AT_2(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, __VA_ARGS__))
#define PP_ARG_AT_3(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, __VA_ARGS__))
#define PP_ARG_AT_4(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, __VA_ARGS__))
#define PP_ARG_AT_5(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, __VA_ARGS__))
#define PP_ARG_AT_6(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, __VA_ARGS__))
#define PP_ARG_AT_7(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, __VA_ARGS__))
#define PP_ARG_AT_8(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, _8, __VA_ARGS__))
#define PP_ARG_AT_9(...)  PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, _7, __VA_ARGS__))
#define PP_ARG_AT_10(...) PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, _6, __VA_ARGS__))
#define PP_ARG_AT_11(...) PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, _5, __VA_ARGS__))
#define PP_ARG_AT_12(...) PP_EXPAND(PP_ARG_POPER(_1, _2, _3, _4, __VA_ARGS__))
#define PP_ARG_AT_13(...) PP_EXPAND(PP_ARG_POPER(_1, _2, _3, __VA_ARGS__))
#define PP_ARG_AT_14(...) PP_EXPAND(PP_ARG_POPER(_1, _2, __VA_ARGS__))
#define PP_ARG_AT_15(...) PP_EXPAND(PP_ARG_POPER(_1, __VA_ARGS__))
#define PP_ARG_AT_16(...) PP_EXPAND(PP_ARG_POPER( __VA_ARGS__))
Solution

  • In C++11, std::max works with initializer_list, so you may use

    std::max({40, 31, 42, 13, 4, 25, 16, 27});

    And if you really want MAX(p1, p2, p3) syntax, you may do:

    #define MAX(...) std::max({__VA_ARGS__})