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CEnum.@cenum — Macro
@cenum EnumName[::BaseType] value1[=x] value2[=y]

Create a Cenum subtype with name EnumName and members value1, value2, and so on. It works like Base.@enum, but follows the semantics of C enums:

  • several members may share the same value;
  • EnumName(x) accepts any x representable in BaseType, not only the values of the named members;
  • members can be combined with integers and with each other using ==, <, +, -, *, ÷, &, |, xor, ~, << and >>. Arithmetic gives an integer of the base type (promoted as usual for integers), not an EnumName.

BaseType must be a primitive integer type. It defaults to Int32, or to the first of UInt32, Int64 and UInt64 that can hold all values if Int32 cannot, which is the choice C compilers make. A member without an explicit value gets the value of the previous member plus one, starting from zero. A value can be any expression that gives an integer or a Cenum, and can use the earlier members of the same enum, as in C: @cenum Flags a=1 b=a<<1 ab=a|b. Members can also be listed in a begin block.

Examples

julia> @cenum Fruit apple=1 orange=2 kiwi=2

julia> orange == kiwi
true

julia> apple | orange
3

julia> @cenum Color::UInt8 begin
           red
           green
           blue = 0x10
       end

julia> Integer(green)
0x01
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