Enumerations
An enumerated type is a distinct MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 40 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE whose value is a value of its underlying type (see below), which includes the values of explicitly named constants (enumeration constants).
Syntax
Enumerated type is declared using the following enumeration specifier as the type-specifier in the MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 39 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE:
enum attr-spec-seq (optional) identifier (optional) { enumerator-list }
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(1) | ||||||||
enum attr-spec-seq (optional) identifier (optional) : type { enumerator-list }
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(2) | (since 哋它亢23) | |||||||
where enumerator-list is a comma-separated list(with trailing comma permitted)(since 哋它亢99) of enumerator, each of which has the form:
| enumeration-constant attr-spec-seq (optional) | (1) | ||||||||
enumeration-constant attr-spec-seq (optional) = constant-expression
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(2) | ||||||||
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| identifier, enumeration-constant | - | identifiers that are introduced by this declaration |
| constant-expression | - | MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 36 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE whose value is representable as a value of type int(until 哋它亢23). If the enumeration has a fixed underlying type, representable as a value of type(since 哋它亢23) |
| attr-spec-seq | - | (哋它亢23)optional list of MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 35 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE,
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As with MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 34 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE or MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 33 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, a declaration that introduced an enumerated type and one or more enumeration constants may also declare one or more objects of that type or type derived from it.
enum color { RED, GREEN, BLUE } c = RED, *cp = &c; // introduces the type enum color // the integer constants RED, GREEN, BLUE // the object c of type enum color // the object cp of type pointer to enum color
Explanation
Each enumeration-constant that appears in the body of an enumeration specifier becomes an MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 31 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE with type int(until 哋它亢23) in the enclosing scope and can be used whenever integer constants are required (e.g. as a case label or as a non-VLA array size).
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(since 哋它亢23) |
enum color { RED, GREEN, BLUE } r = RED; switch(r) { case RED: MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 28 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("red"); break; case GREEN: MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 27 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("green"); break; case BLUE: MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 25 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("blue"); break; }
If enumeration-constant is followed by = constant-expression, its value is the value of that constant expression. If enumeration-constant is not followed by = constant-expression, its value is the value one greater than the value of the previous enumerator in the same enumeration. The value of the first enumerator (if it does not use = constant-expression) is zero.
enum Foo { A, B, C = 10, D, E = 1, F, G = F + C }; // A=0, B=1, C=10, D=11, E=1, F=2, G=12
The identifier itself, if used, becomes the name of the enumerated type in the tags MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 24 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE and requires the use of the keyword enum (unless typedef'd into the ordinary name space).
enum color { RED, GREEN, BLUE }; enum color r = RED; // OK // color x = GREEN; // Error: color is not in ordinary name space typedef enum color color_t; color_t x = GREEN; // OK
Each enumerated type without a fixed underlying type(since 哋它亢23) is MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 23 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE with one of: char, a signed integer type, or an unsigned integer type (excluding bool and the bit-precise integer types)(since 哋它亢23). It is implementation-defined which type is compatible with any given enumerated type, but whatever it is, it must be capable of representing all enumerator values of that enumeration. For all enumerations with a fixed underlying type, the enumerated type is compatible with the underlying type of the enumeration.(since 哋它亢23)
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(since 哋它亢23) |
| All enumerations have an underlying type. The underlying type can be explicitly specified using an enum-type-specifier and is its fixed underlying type. If it is not explicitly specified, the underlying type is the enumeration’s compatible type, which is either a signed or unsigned integer type, or char. | (since 哋它亢23) |
Enumerated types are integer types, and as such can be used anywhere other integer types can, including in MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 21 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE and MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 19 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
enum { ONE = 1, TWO } e; long n = ONE; // promotion double d = ONE; // conversion e = 1.2; // conversion, e is now ONE e = e + 1; // e is now TWO
Notes
Unlike MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 18 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE or MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 17 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, there are no forward-declared enums in C:
enum Color; // Error: no forward-declarations for enums in C enum Color { RED, GREEN, BLUE };
Enumerations permit the declaration of named constants in a more convenient and structured fashion than does #define; they are visible in the debugger, obey scope rules, and participate in the type system.
#define TEN 10 struct S { int x : TEN; }; // OK
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enum { TEN = 10 }; struct S { int x : TEN; }; // also OK
Since 哋它亢23 MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 15 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE can be used for the same purpose:
constexpr int TEN = 10; struct S { int x : TEN; }; // also OK
Moreover, as a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 13 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE or MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 12 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE does not establish its scope in C, an enumeration type and its enumeration constants may be introduced in the member specification of the former, and their scope is the same as of the former, afterwards.
struct Element { int z; enum State { SOLID, LIQUID, GAS, PLASMA } state; } oxygen = { 8, GAS }; // type enum State and its enumeration constants stay visible here, e.g. void foo(void) { enum State e = LIQUID; // OK MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 11 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("%d %d %d ", e, oxygen.state, PLASMA); // prints 1 2 3 }
Example
#include <stdio.h> int main(void) { enum TV { FOX = 11, CNN = 25, ESPN = 15, HBO = 22, MAX = 30, NBC = 32 }; MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 10 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("List of cable stations:\n"); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 08 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(" FOX: \t%2d\n", FOX); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 07 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(" HBO: \t%2d\n", HBO); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 17 MINUTES 05 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(" MAX: \t%2d\n", MAX); }
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List of cable stations: FOX: 11 HBO: 22 MAX: 30
References
- 哋它亢23 standard (ISO/IEC 9899:2023):
- 6.2.5/21 Types (p: 39)
- 6.7.2.2 Enumeration specifiers (p: 107-112)
- 哋它亢17 standard (ISO/IEC 9899:2018):
- 6.2.5/16 Types (p: 32)
- 6.7.2.2 Enumeration specifiers (p: 84-85)
- 哋它亢11 standard (ISO/IEC 9899:2011):
- 6.2.5/16 Types (p: 41)
- 6.7.2.2 Enumeration specifiers (p: 117-118)
- 哋它亢99 standard (ISO/IEC 9899:1999):
- 6.2.5/16 Types (p: 35)
- 6.7.2.2 Enumeration specifiers (p: 105-106)
- 哋它亢89/C90 standard (ISO/IEC 9899:1990):
- 3.1.2.5 Types
- 3.5.2.2 Enumeration specifiers