rs-core

Core utilities

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Enumeration Helpers

Core utility library by Ross Smith

#include "rs-core/enum.hpp"
namespace RS;

Contents

• Enumeration Helpers
  • Contents
  • Concepts
  • Scoped enumeration types
  • Bitmask types

Concepts

template <typename T> concept AutoEnum;
template <typename T> concept AutoBitmask;

These detect enumeration types defined using the macros described below. The AutoEnum concept will match types defined using either macro; AutoBitmask will only match bitmask types.

Scoped enumeration types

#define RS_ENUM(EnumType, IntType, ...)

This macro defines a scoped enumeration type with a user-supplied list of values. It also defines a few additional features around the new type:

• const std::set<EnumType>& enum_values(EnumType)
  • Returns a collection of all the enumeration values. This uses a dummy argument to identify the type (instead of a template parameter) so the function can be found by ADL.
• std::string to_string(EnumType t)
  • Returns the unqualified enumeration value name as a string.
• std::formatter<EnumType>
  • Formatter. The default format is the string returned by to_string().
  • An 'i' flag displays the underlying integer value instead of the name.
  • An 's' flag converts the string to sentence case (ASCII letters only).
  • A 't' flag converts the string to title case (ASCII letters only).
  • A punctuation modifier will replace the underscore in the output string. This can be a space or any ASCII punctuation mark except the six brackets.

The list of enumeration values can include explicit integer values, but the macro does not understand values based on other identifiers or arithmetic expressions. For example, my_volue=0x100 is fine, but my_value=another_value+2 will not work.

Example:

RS_ENUM(MyEnum, int,
    alpha = 1,
    bravo,
    charlie,
)

This is equivalent to:

enum class MyEnum: int {
    alpha = 1,
    bravo,
    charlie,
};

const std::set<MyEnum>& enum_values(MyEnum);
std::string to_string(MyEnum t);
template <> struct std::formatter<MyEnum>;

Bitmask types

#define RS_BITMASK(EnumType, IntType, ...)

This generates all the same features as RS_ENUM(), but also creates a full set of operators that perform bitwise operations on the enumeration type:

constexpr bool operator!(EnumType t) noexcept;
constexpr EnumType operator~(EnumType t) noexcept;
constexpr EnumType operator&(EnumType t, EnumType u) noexcept;
constexpr EnumType operator|(EnumType t, EnumType u) noexcept;
constexpr EnumType operator^(EnumType t, EnumType u) noexcept;
constexpr EnumType& operator&=(EnumType& t, EnumType u) noexcept;
constexpr EnumType& operator|=(EnumType& t, EnumType u) noexcept;
constexpr EnumType& operator^=(EnumType& t, EnumType u) noexcept;

The version of to_string() generated for bitmasks will break down a composite value into its individual named bitmask elements.

Example:

RS_BITMASK(MyBitmask, unsigned,
    none     = 0,
    alpha    = 1,
    bravo    = 2,
    charlie  = 4,
)

auto mask = MyBitmask::alpha | MyBitmask::bravo | MyBitmask::charlie;
std::println("{}", mask);

This will print "alpha|bravo|charlie".