Enums
Enums in Nim are like enums in C, but are type-checked. There are no anonymous enums in Nim.
type
CompassDirections = enum
cdNorth, cdEast, cdSouth, cdWest
Colors {.pure.} = enum
Red = "FF0000", Green = (1, "00FF00"), Blue = "0000FF"
OtherColors {.pure.} = enum
Red = 0xFF0000, Orange = 0xFFA500, Yellow = 0xFFFF00
Signals = enum
sigQuit = 3, sigAbort = 6, sigKill = 9
# echo Red # Error: ambiguous identifier: 'Red'
echo Colors.Red
echo OtherColors.Red
echo OtherColors.Orange, " ", Orange
Notice that each element in CompassDirections
is prepended with cd to avoid name conflicts since references to the enum value do not need to be qualified.
The {.pure.}
pragma that Colors
and OtherColors
have requires that all ambigious references to the enums’ values be qualified. This mean that Orange
can be referred to without OtherColors.Orange
(although OtherColors.Orange
is still allowed).
Enums can be given custom values and stringify values, as shown by Colors and Signals.
Ordinals
While enums can also have disjoint values, it should not be used for any other reason than compatibility with C because it breaks the idea that enums are ordinal.
for direction in ord(low(CompassDirections))..
ord(high(CompassDirections)):
echo CompassDirections(direction), " ord: ", direction
var ordinal = low(int)
inc ordinal
dec ordinal
echo high(char)
Because enums are ordinals, they have the low
, high
, inc
, dec
, and ord
methods defined, where
- low gives the lowest possible value
- high give the highest possible value
- inc increments
- dec decrements
- ord gives the integer value of the enum
- CompassDirections is a cast that gives an enum from an integer
It is also possible to iterate through all possible values of ordinal enums, either as shown above, or cdNorth..cdWest
, which is equivalent.
Signals
is not an ordinal type, and so doesn’t have the inc
and dec
procedures.