Iterating over non-incremental Enum

Question

Before you ask, I\'ve looked and looked for this on SO, and cannot find a solid answer.

I need to be able to dynamically iterate over an enum that has non-incre

Answer 1

Somewhat clearer (???) with a bit of boost preprocessing.

You define your enums by a sequence

#define CAPI_SUBTYPE_E_Sequence \
    (CAPI_SUBTYPE_NULL)(0)  \
    (CAPI_SUBTYPE_DIAG_DFD)(1) ...

then you can automate (through macros) the declaration of the enum,

DECL_ENUM(CAPI_SUBTYPE_E) ;

the table that indexes it

DECL_ENUM_TABLE(CAPI_SUBTYPE_E);

the number of enums / size of the table

ENUM_SIZE(CAPI_SUBTYPE_E)

and access to it:

ITER_ENUM_i(i,CAPI_SUBTYPE_E)

Here is the full text.

#include 

// define your enum as (name)(value) sequence
#define CAPI_SUBTYPE_E_Sequence \
    (CAPI_SUBTYPE_NULL)(0)  /* Null subtype. */ \
    (CAPI_SUBTYPE_DIAG_DFD)(1) /* Data Flow diag. */ \
    (CAPI_SUBTYPE_DIAG_ERD)(2)  /* Entity-Relationship diag. */ \
    (CAPI_SUBTYPE_DIAG_DSD)(5) /* Data Structure diag. */ \
    (CAPI_SUBTYPE_DD_ALL)(13) /* DD Entries (All). */

//  # enums
#define ENUM_SIZE(name) \
    BOOST_PP_DIV(BOOST_PP_SEQ_SIZE(BOOST_PP_CAT(name,_Sequence)),2)

#define ENUM_NAME_N(N,seq) BOOST_PP_SEQ_ELEM(BOOST_PP_MUL(N,2),seq)
#define ENUM_VALUE_N(N,seq) BOOST_PP_SEQ_ELEM(BOOST_PP_INC(BOOST_PP_MUL(N,2)),seq) 

// declare Nth enum
#define DECL_ENUM_N(Z,N,seq) \
    BOOST_PP_COMMA_IF(N)   ENUM_NAME_N(N,seq) =  ENUM_VALUE_N(N,seq)

// declare whole enum
#define DECL_ENUM(name) \
    typedef enum { \
       BOOST_PP_REPEAT( ENUM_SIZE(name) , DECL_ENUM_N , BOOST_PP_CAT(name,_Sequence) ) \
       } name 

DECL_ENUM(CAPI_SUBTYPE_E) ;

// declare Nth enum value
#define DECL_ENUM_TABLE_N(Z,N,seq) \
    BOOST_PP_COMMA_IF(N)   ENUM_NAME_N(N,seq)

// declare table
#define DECL_ENUM_TABLE(name) \
    static const name BOOST_PP_CAT(name,_Table) [ENUM_SIZE(name)] = { \
       BOOST_PP_REPEAT( ENUM_SIZE(name) , DECL_ENUM_TABLE_N , BOOST_PP_CAT(name,_Sequence) ) \
       } 

DECL_ENUM_TABLE(CAPI_SUBTYPE_E);

#define ITER_ENUM_i(i,name)  BOOST_PP_CAT(name,_Table) [i] 

// demo 
// outputs :  [0:0] [1:1] [2:2] [3:5] [4:13]
#include 

int main() {
    for (int i=0; i
#include  

      #define CHECK_ENUM_N(Z,N,seq) \
      BOOST_PP_IF( N , \
      BOOST_STATIC_ASSERT_MSG( \
            ENUM_VALUE_N(BOOST_PP_DEC(N),seq) < ENUM_VALUE_N(N,seq) , \
               BOOST_PP_STRINGIZE( ENUM_NAME_N(BOOST_PP_DEC(N),seq) ) " not < " BOOST_PP_STRINGIZE( ENUM_NAME_N(N,seq) ) ) \
               , ) ;

#define CHECK_ENUM(name) \
    namespace { void BOOST_PP_CAT(check_enum_,name) () { \
    BOOST_PP_REPEAT( ENUM_SIZE(name) , CHECK_ENUM_N , BOOST_PP_CAT(name,_Sequence) )  } }

// enum OK
CHECK_ENUM(CAPI_SUBTYPE_E)

#define Bad_Enum_Sequence \
    (one)(1)\
    (five)(5)\
    (seven)(7)\
    (three)(3)

// enum not OK : enum_iter.cpp(81): error C2338: seven not < three
CHECK_ENUM(Bad_Enum)