JS:
It would be nice to be able to use enums in a hierarchical way:
enum colors
{
enum Red { RedOrange, ... }
enum Green { GreenBlue, ...}
enum Blue { BlueYellow, ... }
...
}
which would be the same as the flattened version,
enum colors
{
Red, RedOrange, ..., Green, GreenBlue, ..., Blue,
BlueYellow, ..., ...
}
but we could dereference such as
colors.Red.RedOrange,
colors.Blue,
colors.Green.GreenBlue,
(This isn't a great example but demonstrates what I would like
to be able to do)
Is anything like this possible?
In Ada you can define ranged types, and there is a keyword to
define their subtypes:
type Day is
(Monday,
Tuesday,
Wednesday,
Thursday,
Friday,
Saturday,
Sunday);
-- Derived types, they are new incompatible with the original:
type Business_Day is new Day range Monday .. Friday;
type Weekend_Day is new Day range Saturday .. Sunday;
-- Subtypes that convert implicitly to their supertype:
subtype Business_Day is Day range Monday .. Friday;
subtype Weekend_Day is Day range Saturday .. Sunday;
subtype Dice_Throw is Integer range 1 .. 6;
The Ada compiler enforces static typing where possible, and uses
dynamic tests where it can't (and the dynamic tests can be
disabled with a compiler switch). So if assign a generic integer
to a Dice_Throw, the Ada compiler performs a run-time test to see
if it's in the correct range.
Ada code is based on similar things that avoid/catch lot of bugs.
Bye,
bearophile
