forked from Alepha/Alepha
Import my EnhancedEnum prototype from enceladus-scratch.
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258
Enum.h
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258
Enum.h
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static_assert( __cplusplus > 2020'00 );
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#pragma once
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#include <cassert>
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#include <tuple>
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#include <string>
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#include <exception>
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#include <stdexcept>
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#include <iostream>
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#include <variant>
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#include <boost/core/demangle.hpp>
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#include "Concepts.h"
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#include "ConstexprString.h"
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#include "evaluation_helpers.h"
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#include "meta.h"
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namespace Alepha::inline Cavorite ::detail:: enhanced_enum
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{
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inline namespace exports {}
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using namespace std::literals::string_literals;
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namespace C
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{
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const bool debug= false;
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const bool debugConstruction= false or C::debug;
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const bool debugCheck= false or C::debug;
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const bool debugConversion= false or C::debug;
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}
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namespace exports
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{
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inline constexpr std::string
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buildAllNames( const std::initializer_list< ConstexprString > &allStrings )
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{
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std::string rv;
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bool first= true;
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for( const auto &str: allStrings )
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{
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if( not first ) rv+= ", ";
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first= false;
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rv+= str.c_str();
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}
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return rv;
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}
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}
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template< auto value, auto ... >
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constexpr decltype( auto )
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get_first_enum_string()
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{
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return value;
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}
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template< ConstexprString s >
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struct EnumValueString
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{
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consteval bool operator == ( EnumValueString ) const { return true; }
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template< ConstexprString alien >
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consteval bool operator == ( EnumValueString< alien > ) const { return false; }
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consteval static ConstexprString cs_string() noexcept { return s; }
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friend std::ostream &
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operator << ( std::ostream &os, const EnumValueString & )
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{
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return os << s;
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}
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};
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template< ConstexprString s, EnumValueString ... reqs >
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concept RequireMatch= ( ... || ( s == reqs.cs_string() ) );
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template< ConstexprString s, EnumValueString ... reqs >
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concept PreventMatch= not RequireMatch< s, reqs... >;
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namespace exports
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{
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inline namespace literals
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{
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template< ConstexprString s >
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consteval auto
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operator ""_value ()
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{
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return EnumValueString< s >{};
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}
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}
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class EnumTextMismatchError : virtual public std::runtime_error
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{
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public:
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using std::runtime_error::runtime_error;
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virtual std::vector< std::string > expectedValues() const= 0;
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};
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template< EnumValueString ... Values > class Enum;
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}
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template< EnumValueString ... values >
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class SpecificEnumTextMismatchError
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: public virtual EnumTextMismatchError
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{
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public:
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using EnumTextMismatchError::EnumTextMismatchError;
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std::vector< std::string >
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expectedValues() const final
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{
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return std::vector< std::string >{ ( values.cs_string().c_str() )... };
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}
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};
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template< EnumValueString ... values >
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class exports::Enum
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//: private comparable
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// Alepha::Hydrogen comparables work differently than the one-off Cavorite form.
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{
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private:
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enum class StrictInteger : unsigned {};
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StrictInteger value= static_cast< StrictInteger >( 0 );
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public:
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static constexpr std::string name() { return buildAllNames( { ( values.cs_string() )... } ); }
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static constexpr bool accepts( const std::string &s ) { return ( ... || ( values.cs_string().c_str() == s ) ); }
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constexpr Enum()= default;
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template< ConstexprString cs_str >
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requires( RequireMatch< cs_str, values... > )
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constexpr
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Enum( EnumValueString< cs_str > )
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{
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if( ( ... && ( cs_str != values.cs_string() ) ) )
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{
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throw std::logic_error( "An enumeration value was specified which is not supported by this `Enum`." );
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}
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unsigned value= 0;
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for( const auto &next: { ( values.cs_string() )... } )
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{
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if( next == cs_str ) break;
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++value;
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}
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set_index( value );
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}
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// ===============================================
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// ========== IMPORANT NOTE ============
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// ===============================================
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//
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// If your compiler gave you an error message that you've called this
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// deleted function, it's almost certainly because you are attempting
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// to assign or otherwise work with an enumerate value which is not
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// supported by the Enhanced Enum in question.
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//
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// Here are some examples.
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//
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// E.g.: `Enum< "1"_value > x= "0"_value;`.
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// E.g.: `Enum< "1"_value >{ "1"_value } == "0"_value`
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//
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// Unfortunately, putting a `static_assert` within the body of
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// this function (for the purpose of providing a nice error message),
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// would make a call to it "well formed", and thus SFINAE would
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// conclude that such a conversion was legal. However, if we don't
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// explicitly delete it, the error message is more confusing.
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//
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// Thankfully, most compilers will point you directly at the attempted
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// deleted call (which is this call, in this case), and thus a suitable
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// helpful comment (such as this one) can hopefully give you some guidance.
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template< ConstexprString cs_str >
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requires( PreventMatch< cs_str, values... > )
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constexpr Enum( EnumValueString< cs_str > )= delete; // PROBABLE ILLEGAL ENUM USAGE. SEE THE NEARBY COMMENTS IN THIS FILE!
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// IMPORTANT:
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//
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// IF YOU GOT HERE FROM A COMPILER ERROR MESSAGE
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// THEN PLEASE SEE THE NOTE ABOVE THIS FUNCTION!!!
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constexpr void
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set_index( const unsigned index )
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{
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if( index >= sizeof...( values ) ) throw std::runtime_error{ "Invalid index set on `Enum`." };
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value= static_cast< StrictInteger >( index );
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}
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constexpr unsigned get_index() const { return static_cast< unsigned >( value ); }
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constexpr auto equality_lens() const { return value; }
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bool operator == ( const Enum & ) const= default;
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friend std::ostream &
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operator << ( std::ostream &os, const Enum &rhs )
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{
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int idx= 0;
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for( const auto &value: { ( values.cs_string() )... } )
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{
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if( idx++ == int( rhs.value ) ) return os << value;
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}
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throw std::logic_error{ "Invalid index detected on `Enum`." };
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}
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friend std::istream &
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operator >> ( std::istream &is, Enum &rhs )
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{
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std::string input;
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is >> input;
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int idx= 0;
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for( const auto &value: { ( values.cs_string() )... } )
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{
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if( input == value.c_str() )
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{
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rhs.value= static_cast< StrictInteger >( idx );
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return is;
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}
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++idx;
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}
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throw SpecificEnumTextMismatchError< values... >( "Invalid argument (`" + input + "`), expected one of {" + rhs.name() + "}" );
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}
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};
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namespace exports
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{
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template< auto ... values >
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constexpr std::string buildAllNames( Enum< values... > ) { return Enum< values... >::name(); }
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template< typename T >
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constexpr bool is_enum_v= false;
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template< EnumValueString ... values >
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constexpr bool is_enum_v< Enum< values... > >{ true };
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}
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}
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namespace Alepha::Cavorite::inline exports::inline enhanced_enum
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{
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using namespace detail::enhanced_enum::exports;
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}
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namespace Alepha::Cavorite::inline exports::inline literals::inline enum_literals
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{
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using namespace detail::enhanced_enum::exports::literals;
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}
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