Re: Let's discuss enums! <pajousek@gmail.com>

On 09/18/2015 10:21 AM, Levi Morrison wrote:

On Fri, Sep 18, 2015 at 1:05 AM, Pavel Kouřil <pajousek@gmail.com> wrote:

On Fri, Sep 18, 2015 at 1:06 AM, Rowan Collins <rowan.collins@gmail.com> wrote:

Hi All, This has come up in passing a few times recently, but I'm not sure there's ever been a dedicated discussion of it: would it be useful for PHP to have a built-in Enumeration type, and if so, how should it look? Many other languages have enum types, with varying functionality. The central concept is always that there's some declared type with a bunch of named constants, but beyond that there's a lot of variability: for starters, is it a type of object, a special way of naming integers, or an uncomparable type more like booleans and nulls? So, what are anyone's thoughts? Am I rambling on too much as usual? ;) Regards, -- Rowan Collins [IMSoP]

Hi, personally, I feel that you should be able to assign numeric value to each element (and have them implicit if not specified). This is imho better for serialization (but it can be done with names as well, yeah) - but more importantly, it also allows usage with bitwise operators, so you could use them as a "flags" (ie. $weekend = Days::SATURDAY | Days::SUNDAY).

In my opinion this is the least valuable form of enums that exists in any language I am aware of. However I was careful in the RFC to not prevent this from being a possibility. I would much, much prefer enums that are more like Rust's, Haskell's or Swift's. It's worth noting Swift has at least three different kinds of enums, one of which would allow the kind of behavior you are wanting.

It may not be valuable in your opinion, but I have seen this kind of enum usage on a lot of open source projects which is really useful to represent more than 1 value in a single variable, which would be more efficient and less memory consuming than doing something like: $weekend = array(

    Days::SATURDAY;
    Days::SUNDAY;

) And anyway, most new languages have over engineered the purpose of enums. Enums should just be a nice way of grouping constant values with a human readable name where the ordinal value should be optionally set for consistency in case that storing it is required. In any case this is a nice read: https://en.wikipedia.org/wiki/Enumerated_type