Repeat Macro -- Cloak

Cloak -- https://github.com/pfultz2/Cloak

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                    )