ओपी के अनुरोध के अनुसार, यहां बूस्ट प्रेप्रोसाइजर और वरियाड मैक्रोज़ पर आधारित बदसूरत मैक्रो समाधान का संस्करण छीन लिया गया है ।
यह एक सरल सूची के लिए अनुमति देता है जैसे कि एन्यूमरेटर तत्वों के सिंटैक्स के साथ विशिष्ट तत्वों के लिए मान सेट करना
XXX_ENUM(foo,(a,b,(c,42)));
तक फैलता है
enum foo {
a,
b,
c=42
};
आउटपुट के लिए आवश्यक कार्यों के साथ और कुछ रूपांतरण वापस करें। यह मैक्रो उम्र के लिए यहाँ आसपास रहा है, और मुझे पूरी तरह से यकीन नहीं है कि इसका सबसे कुशल तरीका है, या यह एक अनुरूप तरीका है, लेकिन यह तब से काम कर रहा है
पूरा कोड Ideone और Coliru दोनों पर कार्रवाई में देखा जा सकता है ।
इसकी गरिमा कुरूपता ऊपर है; मैं इसे आपकी आँखों की सुरक्षा के लिए बिगाड़ने वालों के पीछे डाल देता, अगर मुझे पता होता कि कैसे, लेकिन मार्कडाउन मुझे पसंद नहीं है।
पुस्तकालय (एक एकल हेडर फ़ाइल में विलय)
#include <boost/preprocessor.hpp>
#include <string>
#include <unordered_map>
namespace xxx
{
template<class T>
struct enum_cast_adl_helper { };
template<class E>
E enum_cast( const std::string& s )
{
return do_enum_cast(s,enum_cast_adl_helper<E>());
}
template<class E>
E enum_cast( const char* cs )
{
std::string s(cs);
return enum_cast<E>(s);
}
} // namespace xxx
#define XXX_PP_ARG_N( \
_1, _2, _3, _4, _5, _6, _7, _8, _9,_10, \
_11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \
_21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \
_31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \
_41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \
_51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \
_61,_62,_63,N,...) N
#define XXX_PP_RSEQ_N() \
63,62,61,60, \
59,58,57,56,55,54,53,52,51,50, \
49,48,47,46,45,44,43,42,41,40, \
39,38,37,36,35,34,33,32,31,30, \
29,28,27,26,25,24,23,22,21,20, \
19,18,17,16,15,14,13,12,11,10, \
9,8,7,6,5,4,3,2,1,0
#define XXX_PP_NARG_(...) XXX_PP_ARG_N(__VA_ARGS__)
#define XXX_PP_NARG(...) XXX_PP_NARG_(__VA_ARGS__,XXX_PP_RSEQ_N())
#define XXX_TUPLE_SIZE_INTERNAL(TUPLE) XXX_PP_NARG TUPLE
#define XXX_TUPLE_CHOICE(i) \
BOOST_PP_APPLY( \
BOOST_PP_TUPLE_ELEM( \
25, i, ( \
(0), (1), (2), (3), (4), (5), (6), (7), (8), \
(9), (10), (11), (12), (13), (14), (15), (16), \
(17), (18), (19), (20), (21), (22), (23), (24) \
) ) )
#define BOOST_PP_BOOL_00 BOOST_PP_BOOL_0
#define BOOST_PP_BOOL_01 BOOST_PP_BOOL_1
#define BOOST_PP_BOOL_02 BOOST_PP_BOOL_2
#define BOOST_PP_BOOL_03 BOOST_PP_BOOL_3
#define BOOST_PP_BOOL_04 BOOST_PP_BOOL_4
#define BOOST_PP_BOOL_05 BOOST_PP_BOOL_5
#define BOOST_PP_BOOL_06 BOOST_PP_BOOL_6
#define BOOST_PP_BOOL_07 BOOST_PP_BOOL_7
#define BOOST_PP_BOOL_08 BOOST_PP_BOOL_8
#define BOOST_PP_BOOL_09 BOOST_PP_BOOL_9
#define BOOST_PP_BOOL_010 BOOST_PP_BOOL_10
#define BOOST_PP_BOOL_011 BOOST_PP_BOOL_11
#define BOOST_PP_BOOL_012 BOOST_PP_BOOL_12
#define BOOST_PP_BOOL_013 BOOST_PP_BOOL_13
#define BOOST_PP_BOOL_014 BOOST_PP_BOOL_14
#define BOOST_PP_BOOL_015 BOOST_PP_BOOL_15
#define BOOST_PP_BOOL_016 BOOST_PP_BOOL_16
#define BOOST_PP_BOOL_017 BOOST_PP_BOOL_17
#define BOOST_PP_BOOL_018 BOOST_PP_BOOL_18
#define BOOST_PP_BOOL_019 BOOST_PP_BOOL_19
#define BOOST_PP_BOOL_020 BOOST_PP_BOOL_20
#define BOOST_PP_BOOL_021 BOOST_PP_BOOL_21
#define BOOST_PP_BOOL_022 BOOST_PP_BOOL_22
#define BOOST_PP_BOOL_023 BOOST_PP_BOOL_23
#define BOOST_PP_BOOL_024 BOOST_PP_BOOL_24
#define BOOST_PP_BOOL_025 BOOST_PP_BOOL_25
#define BOOST_PP_BOOL_026 BOOST_PP_BOOL_26
#define BOOST_PP_BOOL_027 BOOST_PP_BOOL_27
#define BOOST_PP_BOOL_028 BOOST_PP_BOOL_28
#define BOOST_PP_BOOL_029 BOOST_PP_BOOL_29
#define BOOST_PP_BOOL_030 BOOST_PP_BOOL_30
#define BOOST_PP_BOOL_031 BOOST_PP_BOOL_31
#define BOOST_PP_BOOL_032 BOOST_PP_BOOL_32
#define BOOST_PP_BOOL_033 BOOST_PP_BOOL_33
#define BOOST_PP_BOOL_034 BOOST_PP_BOOL_34
#define BOOST_PP_BOOL_035 BOOST_PP_BOOL_35
#define BOOST_PP_BOOL_036 BOOST_PP_BOOL_36
#define BOOST_PP_BOOL_037 BOOST_PP_BOOL_37
#define BOOST_PP_BOOL_038 BOOST_PP_BOOL_38
#define BOOST_PP_BOOL_039 BOOST_PP_BOOL_39
#define BOOST_PP_BOOL_040 BOOST_PP_BOOL_40
#define BOOST_PP_BOOL_041 BOOST_PP_BOOL_41
#define BOOST_PP_BOOL_042 BOOST_PP_BOOL_42
#define BOOST_PP_BOOL_043 BOOST_PP_BOOL_43
#define BOOST_PP_BOOL_044 BOOST_PP_BOOL_44
#define BOOST_PP_BOOL_045 BOOST_PP_BOOL_45
#define BOOST_PP_BOOL_046 BOOST_PP_BOOL_46
#define BOOST_PP_BOOL_047 BOOST_PP_BOOL_47
#define BOOST_PP_BOOL_048 BOOST_PP_BOOL_48
#define BOOST_PP_BOOL_049 BOOST_PP_BOOL_49
#define BOOST_PP_BOOL_050 BOOST_PP_BOOL_50
#define BOOST_PP_BOOL_051 BOOST_PP_BOOL_51
#define BOOST_PP_BOOL_052 BOOST_PP_BOOL_52
#define BOOST_PP_BOOL_053 BOOST_PP_BOOL_53
#define BOOST_PP_BOOL_054 BOOST_PP_BOOL_54
#define BOOST_PP_BOOL_055 BOOST_PP_BOOL_55
#define BOOST_PP_BOOL_056 BOOST_PP_BOOL_56
#define BOOST_PP_BOOL_057 BOOST_PP_BOOL_57
#define BOOST_PP_BOOL_058 BOOST_PP_BOOL_58
#define BOOST_PP_BOOL_059 BOOST_PP_BOOL_59
#define BOOST_PP_BOOL_060 BOOST_PP_BOOL_60
#define BOOST_PP_BOOL_061 BOOST_PP_BOOL_61
#define BOOST_PP_BOOL_062 BOOST_PP_BOOL_62
#define BOOST_PP_BOOL_063 BOOST_PP_BOOL_63
#define BOOST_PP_DEC_00 BOOST_PP_DEC_0
#define BOOST_PP_DEC_01 BOOST_PP_DEC_1
#define BOOST_PP_DEC_02 BOOST_PP_DEC_2
#define BOOST_PP_DEC_03 BOOST_PP_DEC_3
#define BOOST_PP_DEC_04 BOOST_PP_DEC_4
#define BOOST_PP_DEC_05 BOOST_PP_DEC_5
#define BOOST_PP_DEC_06 BOOST_PP_DEC_6
#define BOOST_PP_DEC_07 BOOST_PP_DEC_7
#define BOOST_PP_DEC_08 BOOST_PP_DEC_8
#define BOOST_PP_DEC_09 BOOST_PP_DEC_9
#define BOOST_PP_DEC_010 BOOST_PP_DEC_10
#define BOOST_PP_DEC_011 BOOST_PP_DEC_11
#define BOOST_PP_DEC_012 BOOST_PP_DEC_12
#define BOOST_PP_DEC_013 BOOST_PP_DEC_13
#define BOOST_PP_DEC_014 BOOST_PP_DEC_14
#define BOOST_PP_DEC_015 BOOST_PP_DEC_15
#define BOOST_PP_DEC_016 BOOST_PP_DEC_16
#define BOOST_PP_DEC_017 BOOST_PP_DEC_17
#define BOOST_PP_DEC_018 BOOST_PP_DEC_18
#define BOOST_PP_DEC_019 BOOST_PP_DEC_19
#define BOOST_PP_DEC_020 BOOST_PP_DEC_20
#define BOOST_PP_DEC_021 BOOST_PP_DEC_21
#define BOOST_PP_DEC_022 BOOST_PP_DEC_22
#define BOOST_PP_DEC_023 BOOST_PP_DEC_23
#define BOOST_PP_DEC_024 BOOST_PP_DEC_24
#define BOOST_PP_DEC_025 BOOST_PP_DEC_25
#define BOOST_PP_DEC_026 BOOST_PP_DEC_26
#define BOOST_PP_DEC_027 BOOST_PP_DEC_27
#define BOOST_PP_DEC_028 BOOST_PP_DEC_28
#define BOOST_PP_DEC_029 BOOST_PP_DEC_29
#define BOOST_PP_DEC_030 BOOST_PP_DEC_30
#define BOOST_PP_DEC_031 BOOST_PP_DEC_31
#define BOOST_PP_DEC_032 BOOST_PP_DEC_32
#define BOOST_PP_DEC_033 BOOST_PP_DEC_33
#define BOOST_PP_DEC_034 BOOST_PP_DEC_34
#define BOOST_PP_DEC_035 BOOST_PP_DEC_35
#define BOOST_PP_DEC_036 BOOST_PP_DEC_36
#define BOOST_PP_DEC_037 BOOST_PP_DEC_37
#define BOOST_PP_DEC_038 BOOST_PP_DEC_38
#define BOOST_PP_DEC_039 BOOST_PP_DEC_39
#define BOOST_PP_DEC_040 BOOST_PP_DEC_40
#define BOOST_PP_DEC_041 BOOST_PP_DEC_41
#define BOOST_PP_DEC_042 BOOST_PP_DEC_42
#define BOOST_PP_DEC_043 BOOST_PP_DEC_43
#define BOOST_PP_DEC_044 BOOST_PP_DEC_44
#define BOOST_PP_DEC_045 BOOST_PP_DEC_45
#define BOOST_PP_DEC_046 BOOST_PP_DEC_46
#define BOOST_PP_DEC_047 BOOST_PP_DEC_47
#define BOOST_PP_DEC_048 BOOST_PP_DEC_48
#define BOOST_PP_DEC_049 BOOST_PP_DEC_49
#define BOOST_PP_DEC_050 BOOST_PP_DEC_50
#define BOOST_PP_DEC_051 BOOST_PP_DEC_51
#define BOOST_PP_DEC_052 BOOST_PP_DEC_52
#define BOOST_PP_DEC_053 BOOST_PP_DEC_53
#define BOOST_PP_DEC_054 BOOST_PP_DEC_54
#define BOOST_PP_DEC_055 BOOST_PP_DEC_55
#define BOOST_PP_DEC_056 BOOST_PP_DEC_56
#define BOOST_PP_DEC_057 BOOST_PP_DEC_57
#define BOOST_PP_DEC_058 BOOST_PP_DEC_58
#define BOOST_PP_DEC_059 BOOST_PP_DEC_59
#define BOOST_PP_DEC_060 BOOST_PP_DEC_60
#define BOOST_PP_DEC_061 BOOST_PP_DEC_61
#define BOOST_PP_DEC_062 BOOST_PP_DEC_62
#define BOOST_PP_DEC_063 BOOST_PP_DEC_63
#define XXX_TO_NUMx(x) 0 ## x
#define XXX_TO_NUM(x) BOOST_PP_ADD(0,XXX_TO_NUMx(x))
#define XXX_STRINGIZEX(x) # x
#define XXX_VSTRINGIZE_SINGLE(a,b,x) XXX_STRINGIZE(x)
#define XXX_VSTRINGIZE_TUPLE(tpl) XXX_TUPLE_FOR_EACH(XXX_VSTRINGIZE_SINGLE,,tpl)
#define XXX_TUPLE_SIZE(TUPLE) XXX_TO_NUM(XXX_TUPLE_CHOICE(XXX_TUPLE_SIZE_INTERNAL(TUPLE)))
#define XXX_TUPLE_FOR_EACH(MACRO,DATA,TUPLE) BOOST_PP_LIST_FOR_EACH(MACRO,DATA,BOOST_PP_TUPLE_TO_LIST(XXX_TUPLE_SIZE(TUPLE),TUPLE))
#define XXX_STRINGIZE(x) XXX_STRINGIZEX(x)
#define XXX_VSTRINGIZE(...) XXX_VSTRINGIZE_TUPLE((__VA_ARGS__))
#define XXX_CAST_TO_VOID_ELEMENT(r,data,elem) (void)(elem);
#define XXX_CAST_TO_VOID_INTERNAL(TUPLE) XXX_TUPLE_FOR_EACH(XXX_CAST_TO_VOID_ELEMENT,,TUPLE)
#define XXX_CAST_TO_VOID(...) XXX_CAST_TO_VOID_INTERNAL((__VA_ARGS__))
#define XXX_ENUM_EXTRACT_SP(en) BOOST_PP_TUPLE_ELEM(XXX_TUPLE_SIZE(en),0,en) = BOOST_PP_TUPLE_ELEM(XXX_TUPLE_SIZE(en),1,en)
#define XXX_ENUM_ELEMENT(r,data,elem) BOOST_PP_IF( XXX_TUPLE_SIZE(elem), XXX_ENUM_EXTRACT_SP(elem), elem) ,
#define XXX_ENUM_EXTRACT_ELEMENT(en) BOOST_PP_TUPLE_ELEM(XXX_TUPLE_SIZE(en),0,en)
#define XXX_ENUM_CASE_ELEMENT(en) BOOST_PP_IF( XXX_TUPLE_SIZE(en), XXX_ENUM_EXTRACT_ELEMENT(en), en )
#define XXX_ENUM_CASE(r,data,elem) case data :: XXX_ENUM_CASE_ELEMENT(elem) : return #data "::" XXX_STRINGIZE(XXX_ENUM_CASE_ELEMENT(elem));
#define XXX_ENUM_IFELSE(r,data,elem) else if( en == data :: XXX_ENUM_CASE_ELEMENT(elem)) { return #data "::" XXX_STRINGIZE(XXX_ENUM_CASE_ELEMENT(elem)); }
#define XXX_ENUM_CASTLIST(r,data,elem) { XXX_STRINGIZE(XXX_ENUM_CASE_ELEMENT(elem)), data :: XXX_ENUM_CASE_ELEMENT(elem) },
#define XXX_ENUM_QUALIFIED_CASTLIST(r,data,elem) { #data "::" XXX_STRINGIZE(XXX_ENUM_CASE_ELEMENT(elem)), data :: XXX_ENUM_CASE_ELEMENT(elem) },
#define XXX_ENUM_INTERNAL(TYPE,NAME,TUPLE) \
enum TYPE \
{ \
XXX_TUPLE_FOR_EACH(XXX_ENUM_ELEMENT,,TUPLE) \
BOOST_PP_CAT(last_enum_,NAME) \
}; \
\
inline \
const char* to_string( NAME en ) \
{ \
if(false) \
{ \
} \
XXX_TUPLE_FOR_EACH(XXX_ENUM_IFELSE,NAME,TUPLE) \
else if( en == NAME :: BOOST_PP_CAT(last_enum_,NAME) ) \
{ \
return XXX_VSTRINGIZE(NAME,::,BOOST_PP_CAT(last_enum_,NAME)); \
} \
else \
{ \
return "Invalid enum value specified for " # NAME; \
} \
} \
\
inline \
std::ostream& operator<<( std::ostream& os, const NAME& en ) \
{ \
os << to_string(en); \
return os; \
} \
\
inline \
NAME do_enum_cast( const std::string& s, const ::xxx::enum_cast_adl_helper<NAME>& ) \
{ \
static const std::unordered_map<std::string,NAME> map = \
{ \
XXX_TUPLE_FOR_EACH(XXX_ENUM_CASTLIST,NAME,TUPLE) \
XXX_TUPLE_FOR_EACH(XXX_ENUM_QUALIFIED_CASTLIST,NAME,TUPLE) \
}; \
\
auto cit = map.find(s); \
if( cit == map.end() ) \
{ \
throw std::runtime_error("Invalid value to cast to enum"); \
} \
return cit->second; \
}
#define XXX_ENUM(NAME,TUPLE) XXX_ENUM_INTERNAL(NAME,NAME,TUPLE)
#define XXX_ENUM_CLASS(NAME,TUPLE) XXX_ENUM_INTERNAL(class NAME,NAME,TUPLE)
#define XXX_ENUM_CLASS_TYPE(NAME,TYPE,TUPLE) XXX_ENUM_INTERNAL(class NAME : TYPE,NAME,TUPLE)
#define XXX_ENUM_TYPE(NAME,TYPE,TUPLE) XXX_ENUM_INTERNAL(NAME : TYPE,NAME,TUPLE)
प्रयोग
#include "xxx_enum.h" // the above lib
#include <iostream>
XXX_ENUM(foo,(a,b,(c,42)));
int main()
{
std::cout << "foo::a = " << foo::a <<'\n';
std::cout << "(int)foo::c = " << (int)foo::c <<'\n';
std::cout << "to_string(foo::b) = " << to_string(foo::b) <<'\n';
std::cout << "xxx::enum_cast<foo>(\"b\") = " << xxx::enum_cast<foo>("b") <<'\n';
}
संकलन (कॉपी पेस्ट हेडर भीतर main.cpp)
> g++ --version | sed 1q
g++ (GCC) 4.9.2
> g++ -std=c++14 -pedantic -Wall -Wextra main.cpp
main.cpp:268:31: warning: extra ';' [-Wpedantic]
XXX_ENUM(foo,(a,b,(c,42)));
^
उत्पादन
foo::a = foo::a
(int)foo::c = 42
to_string(foo::b) = foo::b
xxx::enum_cast<foo>("b") = foo::b