A mini-preprocessor library to demostrate the recursive capabilites of the preprocessor
#define CAT(a, ...) PRIMITIVE_CAT(a, __VA_ARGS__) #define PRIMITIVE_CAT(a, ...) a ## __VA_ARGS__ #define INC(x) PRIMITIVE_CAT(INC_, x) #define INC_0 1 #define INC_1 2 #define INC_2 3 #define INC_3 4 #define INC_4 5 #define INC_5 6 #define INC_6 7 #define INC_7 8 #define INC_8 9 #define INC_9 9 #define DEC(x) PRIMITIVE_CAT(DEC_, x) #define DEC_0 0 #define DEC_1 0 #define DEC_2 1 #define DEC_3 2 #define DEC_4 3 #define DEC_5 4 #define DEC_6 5 #define DEC_7 6 #define DEC_8 7 #define DEC_9 8 #define EXPR_S(s) PRIMITIVE_CAT(EXPR_, s) #define EXPR_0(...) __VA_ARGS__ #define EXPR_1(...) __VA_ARGS__ #define EXPR_2(...) __VA_ARGS__ #define EXPR_3(...) __VA_ARGS__ #define EXPR_4(...) __VA_ARGS__ #define EXPR_5(...) __VA_ARGS__ #define EXPR_6(...) __VA_ARGS__ #define EXPR_7(...) __VA_ARGS__ #define EXPR_8(...) __VA_ARGS__ #define EXPR_9(...) __VA_ARGS__ #define CHECK_N(x, n, ...) n #define CHECK(...) CHECK_N(__VA_ARGS__, 0,) #define NOT(x) CHECK(PRIMITIVE_CAT(NOT_, x)) #define NOT_0 ~, 1, #define COMPL(b) PRIMITIVE_CAT(COMPL_, b) #define COMPL_0 1 #define COMPL_1 0 #define BOOL(x) COMPL(NOT(x)) #define IIF(c) PRIMITIVE_CAT(IIF_, c) #define IIF_0(t, ...) __VA_ARGS__ #define IIF_1(t, ...) t #define IF(c) IIF(BOOL(c)) #define COMMA() , #define COMMA_IF(n) IF(n)(COMMA, EAT)() // IF( cond )( cond_ture, cond_false ) #define EAT(...) #define EXPAND(...) __VA_ARGS__#define WHEN(c) IF(c)(EXPAND, EAT)// IF( cond )( __VA_ARGS__, /* nothing */ ) #define EMPTY() #define DEFER(id) id EMPTY() #define OBSTRUCT(id) id DEFER(EMPTY)() // as first parameter to make it easier and cleaner to write a deferred expression in theimplemnentation// So instead of writing DEFER(WHEN)(n), we will just write WHEN _(n) // s : recursion state ( 0, 1 --> N+1 )// n : repeater counter ( N, N-1 --> 0 )// m : macro// ... : __VA_ARGS__ for m// #define REPEAT_S(s, n, m, ...) REPEAT_I( OBSTRUCT(), INC(s), n, m, __VA_ARGS__) #define REPEAT_INDIRECT() REPEAT_I #define REPEAT_I(_, s, n, m, ...) WHEN _(n) ( EXPR_S _(s) ( REPEAT_INDIRECT _() ( OBSTRUCT _(), INC _(s), DEC _(n), m, __VA_ARGS__) ) ) m _(s, n, __VA_ARGS__) IF (c) ( EXPAND, EAT )
转载于:https://www.cnblogs.com/shangdawei/archive/2013/05/28/3104834.html
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