只需要生成枚举。为此目的编写一个生成器大约需要5分钟的工作。

生成器代码在java和python，超级容易移植到任何你喜欢的语言，包括c++。

而且非常容易扩展任何你想要的功能。

示例输入:

First = 5
Second
Third = 7
Fourth
Fifth=11

生成头文件:

#include <iosfwd>

enum class Hallo
{
    First = 5,
    Second = 6,
    Third = 7,
    Fourth = 8,
    Fifth = 11
};

std::ostream & operator << (std::ostream &, const Hallo&);

生成的CPP文件

#include <ostream>

#include "Hallo.h"

std::ostream & operator << (std::ostream &out, const Hallo&value)
{
    switch(value)
    {
    case Hallo::First:
        out << "First";
        break;
    case Hallo::Second:
        out << "Second";
        break;
    case Hallo::Third:
        out << "Third";
        break;
    case Hallo::Fourth:
        out << "Fourth";
        break;
    case Hallo::Fifth:
        out << "Fifth";
        break;
    default:
        out << "<unknown>";
    }

    return out;
}

生成器以非常简洁的形式作为移植和扩展的模板。这个示例代码确实试图避免覆盖任何文件，但使用它仍然要自担风险。

package cppgen;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.Charset;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class EnumGenerator
{
    static void fail(String message)
    {
        System.err.println(message);
        System.exit(1);
    }

    static void run(String[] args)
    throws Exception
    {
        Pattern pattern = Pattern.compile("\\s*(\\w+)\\s*(?:=\\s*(\\d+))?\\s*", Pattern.UNICODE_CHARACTER_CLASS);
        Charset charset = Charset.forName("UTF8");
        String tab = "    ";

        if (args.length != 3)
        {
            fail("Required arguments: <enum name> <input file> <output dir>");
        }

        String enumName = args[0];

        File inputFile = new File(args[1]);

        if (inputFile.isFile() == false)
        {
            fail("Not a file: [" + inputFile.getCanonicalPath() + "]");
        }

        File outputDir = new File(args[2]);

        if (outputDir.isDirectory() == false)
        {
            fail("Not a directory: [" + outputDir.getCanonicalPath() + "]");
        }

        File headerFile = new File(outputDir, enumName + ".h");
        File codeFile = new File(outputDir, enumName + ".cpp");

        for (File file : new File[] { headerFile, codeFile })
        {
            if (file.exists())
            {
                fail("Will not overwrite file [" + file.getCanonicalPath() + "]");
            }
        }

        int nextValue = 0;

        Map<String, Integer> fields = new LinkedHashMap<>();

        try
        (
            BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(inputFile), charset));
        )
        {
            while (true)
            {
                String line = reader.readLine();

                if (line == null)
                {
                    break;
                }

                if (line.trim().length() == 0)
                {
                    continue;
                }

                Matcher matcher = pattern.matcher(line);

                if (matcher.matches() == false)
                {
                    fail("Syntax error: [" + line + "]");
                }

                String fieldName = matcher.group(1);

                if (fields.containsKey(fieldName))
                {
                    fail("Double fiend name: " + fieldName);
                }

                String valueString = matcher.group(2);

                if (valueString != null)
                {
                    int value = Integer.parseInt(valueString);

                    if (value < nextValue)
                    {
                        fail("Not a monotonous progression from " + nextValue + " to " + value + " for enum field " + fieldName);
                    }

                    nextValue = value;
                }

                fields.put(fieldName, nextValue);

                ++nextValue;
            }
        }

        try
        (
            PrintWriter headerWriter = new PrintWriter(new OutputStreamWriter(new FileOutputStream(headerFile), charset));
            PrintWriter codeWriter = new PrintWriter(new OutputStreamWriter(new FileOutputStream(codeFile), charset));
        )
        {
            headerWriter.println();
            headerWriter.println("#include <iosfwd>");
            headerWriter.println();
            headerWriter.println("enum class " + enumName);
            headerWriter.println('{');
            boolean first = true;
            for (Entry<String, Integer> entry : fields.entrySet())
            {
                if (first == false)
                {
                    headerWriter.println(",");
                }

                headerWriter.print(tab + entry.getKey() + " = " + entry.getValue());

                first = false;
            }
            if (first == false)
            {
                headerWriter.println();
            }
            headerWriter.println("};");
            headerWriter.println();
            headerWriter.println("std::ostream & operator << (std::ostream &, const " + enumName + "&);");
            headerWriter.println();

            codeWriter.println();
            codeWriter.println("#include <ostream>");
            codeWriter.println();
            codeWriter.println("#include \"" + enumName + ".h\"");
            codeWriter.println();
            codeWriter.println("std::ostream & operator << (std::ostream &out, const " + enumName + "&value)");
            codeWriter.println('{');
            codeWriter.println(tab + "switch(value)");
            codeWriter.println(tab + '{');
            first = true;
            for (Entry<String, Integer> entry : fields.entrySet())
            {
                codeWriter.println(tab + "case " + enumName + "::" + entry.getKey() + ':');
                codeWriter.println(tab + tab + "out << \"" + entry.getKey() + "\";");
                codeWriter.println(tab + tab + "break;");

                first = false;
            }
            codeWriter.println(tab + "default:");
            codeWriter.println(tab + tab + "out << \"<unknown>\";");
            codeWriter.println(tab + '}');
            codeWriter.println();
            codeWriter.println(tab + "return out;");
            codeWriter.println('}');
            codeWriter.println();
        }
    }

    public static void main(String[] args)
    {
        try
        {
            run(args);
        }
        catch(Exception exc)
        {
            exc.printStackTrace();
            System.exit(1);
        }
    }
}

并将其移植到Python 3.5，因为它的不同可能会有所帮助

import re
import collections
import sys
import io
import os

def fail(*args):
    print(*args)
    exit(1)

pattern = re.compile(r'\s*(\w+)\s*(?:=\s*(\d+))?\s*')
tab = "    "

if len(sys.argv) != 4:
    n=0
    for arg in sys.argv:
        print("arg", n, ":", arg, " / ", sys.argv[n])
        n += 1
    fail("Required arguments: <enum name> <input file> <output dir>")

enumName = sys.argv[1]

inputFile = sys.argv[2]

if not os.path.isfile(inputFile):
    fail("Not a file: [" + os.path.abspath(inputFile) + "]")

outputDir = sys.argv[3]

if not os.path.isdir(outputDir):
    fail("Not a directory: [" + os.path.abspath(outputDir) + "]")

headerFile = os.path.join(outputDir, enumName + ".h")
codeFile = os.path.join(outputDir, enumName + ".cpp")

for file in [ headerFile, codeFile ]:
    if os.path.exists(file):
        fail("Will not overwrite file [" + os.path.abspath(file) + "]")

nextValue = 0

fields = collections.OrderedDict()

for line in open(inputFile, 'r'):
    line = line.strip()

    if len(line) == 0:
        continue

    match = pattern.match(line)

    if match == None:
        fail("Syntax error: [" + line + "]")

    fieldName = match.group(1)

    if fieldName in fields:
        fail("Double field name: " + fieldName)

    valueString = match.group(2)

    if valueString != None:
        value = int(valueString)

        if value < nextValue:
            fail("Not a monotonous progression from " + nextValue + " to " + value + " for enum field " + fieldName)

        nextValue = value

    fields[fieldName] = nextValue

    nextValue += 1

headerWriter = open(headerFile, 'w')
codeWriter = open(codeFile, 'w')

try:
    headerWriter.write("\n")
    headerWriter.write("#include <iosfwd>\n")
    headerWriter.write("\n")
    headerWriter.write("enum class " + enumName + "\n")
    headerWriter.write("{\n")
    first = True
    for fieldName, fieldValue in fields.items():
        if not first:
            headerWriter.write(",\n")

        headerWriter.write(tab + fieldName + " = " + str(fieldValue))

        first = False
    if not first:
        headerWriter.write("\n")
    headerWriter.write("};\n")
    headerWriter.write("\n")
    headerWriter.write("std::ostream & operator << (std::ostream &, const " + enumName + "&);\n")
    headerWriter.write("\n")

    codeWriter.write("\n")
    codeWriter.write("#include <ostream>\n")
    codeWriter.write("\n")
    codeWriter.write("#include \"" + enumName + ".h\"\n")
    codeWriter.write("\n")
    codeWriter.write("std::ostream & operator << (std::ostream &out, const " + enumName + "&value)\n")
    codeWriter.write("{\n")
    codeWriter.write(tab + "switch(value)\n")
    codeWriter.write(tab + "{\n")
    for fieldName in fields.keys():
        codeWriter.write(tab + "case " + enumName + "::" + fieldName + ":\n")
        codeWriter.write(tab + tab + "out << \"" + fieldName + "\";\n")
        codeWriter.write(tab + tab + "break;\n")
    codeWriter.write(tab + "default:\n")
    codeWriter.write(tab + tab + "out << \"<unknown>\";\n")
    codeWriter.write(tab + "}\n")
    codeWriter.write("\n")
    codeWriter.write(tab + "return out;\n")
    codeWriter.write("}\n")
    codeWriter.write("\n")
finally:
    headerWriter.close()
    codeWriter.close()

我不知道你是否会喜欢这个，我对这个解决方案不太满意，但它是一个c++ 14友好的方法，因为它使用模板变量和滥用模板专门化:

enum class MyEnum : std::uint_fast8_t {
   AAA,
   BBB,
   CCC,
};

template<MyEnum> const char MyEnumName[] = "Invalid MyEnum value";
template<> const char MyEnumName<MyEnum::AAA>[] = "AAA";
template<> const char MyEnumName<MyEnum::BBB>[] = "BBB";
template<> const char MyEnumName<MyEnum::CCC>[] = "CCC";

int main()
{
    // Prints "AAA"
    std::cout << MyEnumName<MyEnum::AAA> << '\n';
    // Prints "Invalid MyEnum value"
    std::cout << MyEnumName<static_cast<MyEnum>(0x12345678)> << '\n';
    // Well... in fact it prints "Invalid MyEnum value" for any value
    // different of MyEnum::AAA, MyEnum::BBB or MyEnum::CCC.

    return 0;
}

这种方法最糟糕的地方是维护起来很痛苦，但维护其他一些类似的方法也很痛苦，不是吗?

这种方法的优点:

使用可变温度(c++ 14特性) 使用模板专门化，我们可以在使用无效值时“检测”(但我不确定这是否有用)。 看起来很整洁。 名称查找在编译时完成。

生活的例子

Edit

你是对的;c++ 14变量模板方法不处理运行时情况，这是我的错，忘记了它:(

但是我们仍然可以使用一些现代c++特性和变量模板加上变进模板技巧来实现从枚举值到字符串的运行时转换…它和其他一样麻烦，但仍然值得一提。

让我们开始使用模板别名来缩短对枚举到字符串映射的访问:

// enum_map contains pairs of enum value and value string for each enum
// this shortcut allows us to use enum_map<whatever>.
template <typename ENUM>
using enum_map = std::map<ENUM, const std::string>;

// This variable template will create a map for each enum type which is
// instantiated with.
template <typename ENUM>
enum_map<ENUM> enum_values{};

然后，变值模板诡计:

template <typename ENUM>
void initialize() {}

template <typename ENUM, typename ... args>
void initialize(const ENUM value, const char *name, args ... tail)
{
    enum_values<ENUM>.emplace(value, name);
    initialize<ENUM>(tail ...);
}

这里的“最佳技巧”是为map使用变量template，其中包含每个枚举条目的值和名称;这个映射在每个翻译单元中都是相同的，并且到处都有相同的名称，所以非常简单明了，如果我们像这样调用initialize函数:

initialize
(
    MyEnum::AAA, "AAA",
    MyEnum::BBB, "BBB",
    MyEnum::CCC, "CCC"
);

我们正在为每个MyEnum条目签名，并且可以在运行时使用:

std::cout << enum_values<MyEnum>[MyEnum::AAA] << '\n';

但是可以通过SFINAE和重载<<运算符进行改进:

template<typename ENUM, class = typename std::enable_if<std::is_enum<ENUM>::value>::type>
std::ostream &operator <<(std::ostream &o, const ENUM value)
{
    static const std::string Unknown{std::string{typeid(ENUM).name()} + " unknown value"};
    auto found = enum_values<ENUM>.find(value);

    return o << (found == enum_values<ENUM>.end() ? Unknown : found->second);
}

使用正确的操作符<<，现在我们可以这样使用枚举:

std::cout << MyEnum::AAA << '\n';

维护这一点也很麻烦，可以改进，但希望您能理解。

生活的例子

这个要点提供了一个基于c++可变参数模板的简单映射。

这是一个c++ 17简化版的基于类型的映射的要点:

#include <cstring> // http://stackoverflow.com/q/24520781

template<typename KeyValue, typename ... RestOfKeyValues>
struct map {
  static constexpr typename KeyValue::key_t get(const char* val) noexcept {
    if constexpr (sizeof...(RestOfKeyValues)==0)  // C++17 if constexpr
      return KeyValue::key; // Returns last element
    else {
      static_assert(KeyValue::val != nullptr,
                  "Only last element may have null name");
      return strcmp(val, KeyValue::val()) 
            ? map<RestOfKeyValues...>::get(val) : KeyValue::key;
    }
  }
  static constexpr const char* get(typename KeyValue::key_t key) noexcept {
    if constexpr (sizeof...(RestOfKeyValues)==0)
      return (KeyValue::val != nullptr) && (key == KeyValue::key)
            ? KeyValue::val() : "";
    else
      return (key == KeyValue::key) 
            ? KeyValue::val() : map<RestOfKeyValues...>::get(key);
  }
};

template<typename Enum, typename ... KeyValues>
class names {
  typedef map<KeyValues...> Map;
public:
  static constexpr Enum get(const char* nam) noexcept {
    return Map::get(nam);
  }
  static constexpr const char* get(Enum key) noexcept {
    return Map::get(key);
  }
};

用法示例:

enum class fasion {
    fancy,
    classic,
    sporty,
    emo,
    __last__ = emo,
    __unknown__ = -1
};

#define NAME(s) static inline constexpr const char* s() noexcept {return #s;}
namespace name {
    NAME(fancy)
    NAME(classic)
    NAME(sporty)
    NAME(emo)
}

template<auto K, const char* (*V)()>  // C++17 template<auto>
struct _ {
    typedef decltype(K) key_t;
    typedef decltype(V) name_t;
    static constexpr key_t  key = K; // enum id value
    static constexpr name_t val = V; // enum id name
};

typedef names<fasion,
    _<fasion::fancy, name::fancy>,
    _<fasion::classic, name::classic>,
    _<fasion::sporty, name::sporty>,
    _<fasion::emo, name::emo>,
    _<fasion::__unknown__, nullptr>
> fasion_names;

map < keyvalue…>可以双向使用:

fasion_names:把(in fashion: emo) fasion_names::把(“emo”)

这个例子可以在godbolt.org上找到

int main ()
{
  constexpr auto str = fasion_names::get(fasion::emo);
  constexpr auto fsn = fasion_names::get(str);
  return (int) fsn;
}

结果:gc -7 -std=c++1z -Ofast -S

main:
        mov     eax, 3
        ret

根据OP的要求，这里有一个基于Boost preproessor和Variadic Macros的丑陋宏解决方案的精简版本。

它允许类似枚举元素语法的简单列表，并为特定元素设置值，以便

XXX_ENUM(foo,(a,b,(c,42)));

扩大到

enum foo {
    a,
    b,
    c=42
};

与必要的函数一起输出并做一些转换。这个宏已经存在了很长时间，我不完全确定这是最有效的方式，或者它是一种一致的方式，但它一直以来都在工作

完整的代码可以在Ideone和Coliru中看到。

它的巨大丑陋在上面;如果我知道怎么做，我会把它放在剧透后面保护你的眼睛，但markdown不喜欢我。

库(合并在一个头文件中)

#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)

使用

#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';
}

编译(在main.cpp中复制粘贴头文件)

> 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)));
                               ^

输出

foo::a = foo::a
(int)foo::c = 42
to_string(foo::b) = foo::b
xxx::enum_cast<foo>("b") = foo::b

你可以滥用用户定义的文字来达到想要的结果:

enum
{
  AAA = "AAA"_h8,
  BB = "BB"_h8,
};
   
std::cout << h8::to_string(AAA) << std::endl;
std::cout << h8::to_string(BB) << std::endl;

这将一个字符串打包成一个整数，这是可逆的。请看这里的例子。

这和尤里·芬克尔斯坦的观点相似;但不需要提高。我正在使用一个地图，所以你可以分配任何值枚举，任何顺序。

枚举类的声明为:

DECLARE_ENUM_WITH_TYPE(TestEnumClass, int32_t, ZERO = 0x00, TWO = 0x02, ONE = 0x01, THREE = 0x03, FOUR);

下面的代码将自动创建枚举类并重载:

'+' '+='用于std::string '<<'用于流 '~'只是转换为字符串(任何一元运算符都可以，但我个人不喜欢它的清晰度) '*'获取枚举的计数

不需要boost，提供所有需要的功能。

代码:

#include <algorithm>
#include <iostream>
#include <map>
#include <sstream>
#include <string>
#include <vector>

#define STRING_REMOVE_CHAR(str, ch) str.erase(std::remove(str.begin(), str.end(), ch), str.end())

std::vector<std::string> splitString(std::string str, char sep = ',') {
    std::vector<std::string> vecString;
    std::string item;

    std::stringstream stringStream(str);

    while (std::getline(stringStream, item, sep))
    {
        vecString.push_back(item);
    }

    return vecString;
}

#define DECLARE_ENUM_WITH_TYPE(E, T, ...)                                                                     \
    enum class E : T                                                                                          \
    {                                                                                                         \
        __VA_ARGS__                                                                                           \
    };                                                                                                        \
    std::map<T, std::string> E##MapName(generateEnumMap<T>(#__VA_ARGS__));                                    \
    std::ostream &operator<<(std::ostream &os, E enumTmp)                                                     \
    {                                                                                                         \
        os << E##MapName[static_cast<T>(enumTmp)];                                                            \
        return os;                                                                                            \
    }                                                                                                         \
    size_t operator*(E enumTmp) { (void) enumTmp; return E##MapName.size(); }                                 \
    std::string operator~(E enumTmp) { return E##MapName[static_cast<T>(enumTmp)]; }                          \
    std::string operator+(std::string &&str, E enumTmp) { return str + E##MapName[static_cast<T>(enumTmp)]; } \
    std::string operator+(E enumTmp, std::string &&str) { return E##MapName[static_cast<T>(enumTmp)] + str; } \
    std::string &operator+=(std::string &str, E enumTmp)                                                      \
    {                                                                                                         \
        str += E##MapName[static_cast<T>(enumTmp)];                                                           \
        return str;                                                                                           \
    }                                                                                                         \
    E operator++(E &enumTmp)                                                                                  \
    {                                                                                                         \
        auto iter = E##MapName.find(static_cast<T>(enumTmp));                                                 \
        if (iter == E##MapName.end() || std::next(iter) == E##MapName.end())                                  \
            iter = E##MapName.begin();                                                                        \
        else                                                                                                  \
        {                                                                                                     \
            ++iter;                                                                                           \
        }                                                                                                     \
        enumTmp = static_cast<E>(iter->first);                                                                \
        return enumTmp;                                                                                       \
    }                                                                                                         \
    bool valid##E(T value) { return (E##MapName.find(value) != E##MapName.end()); }

#define DECLARE_ENUM(E, ...) DECLARE_ENUM_WITH_TYPE(E, int32_t, __VA_ARGS__)
template <typename T>
std::map<T, std::string> generateEnumMap(std::string strMap)
{
    STRING_REMOVE_CHAR(strMap, ' ');
    STRING_REMOVE_CHAR(strMap, '(');

    std::vector<std::string> enumTokens(splitString(strMap));
    std::map<T, std::string> retMap;
    T inxMap;

    inxMap = 0;
    for (auto iter = enumTokens.begin(); iter != enumTokens.end(); ++iter)
    {
        // Token: [EnumName | EnumName=EnumValue]
        std::string enumName;
        T enumValue;
        if (iter->find('=') == std::string::npos)
        {
            enumName = *iter;
        }
        else
        {
            std::vector<std::string> enumNameValue(splitString(*iter, '='));
            enumName = enumNameValue[0];
            //inxMap = static_cast<T>(enumNameValue[1]);
            if (std::is_unsigned<T>::value)
            {
                inxMap = static_cast<T>(std::stoull(enumNameValue[1], 0, 0));
            }
            else
            {
                inxMap = static_cast<T>(std::stoll(enumNameValue[1], 0, 0));
            }
        }
        retMap[inxMap++] = enumName;
    }

    return retMap;
}

例子:

DECLARE_ENUM_WITH_TYPE(TestEnumClass, int32_t, ZERO = 0x00, TWO = 0x02, ONE = 0x01, THREE = 0x03, FOUR);

int main(void) {
    TestEnumClass first, second;
    first = TestEnumClass::FOUR;
    second = TestEnumClass::TWO;

    std::cout << first << "(" << static_cast<uint32_t>(first) << ")" << std::endl; // FOUR(4)

    std::string strOne;
    strOne = ~first;
    std::cout << strOne << std::endl; // FOUR

    std::string strTwo;
    strTwo = ("Enum-" + second) + (TestEnumClass::THREE + "-test");
    std::cout << strTwo << std::endl; // Enum-TWOTHREE-test

    std::string strThree("TestEnumClass: ");
    strThree += second;
    std::cout << strThree << std::endl; // TestEnumClass: TWO
    std::cout << "Enum count=" << *first << std::endl;
}

您可以在这里运行代码