(CC'ing internals as it was apparently dropped by Jeff) On Fri, Sep 18, 2015 at 11:03 AM, Levi Morrison <le...@php.net> wrote: > On Fri, Sep 18, 2015 at 9:59 AM, Jefferson Gonzalez <jgm...@gmail.com> wrote: >> On 09/18/2015 10:21 AM, Levi Morrison wrote: >>> >>> On Fri, Sep 18, 2015 at 1:05 AM, Pavel Kouřil <pajou...@gmail.com> wrote: >>>> >>>> On Fri, Sep 18, 2015 at 1:06 AM, Rowan Collins <rowan.coll...@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. > > According to type theory the enumerated type is just a special case of > the union type where each type constructor in the union takes exactly > zero parameters (meaning they are all singletons). So… what is the > purpose of an enumerated type? To create a finite set of values that > are all unique. That's it – that's the whole purpose. > > Anything else is trying to add value in some way – in your case you > are adding a primitive value that the language will automatically map > for you. I'm not saying that is a bad thing but I hope you can at > least recognize that it is an addition and not the bare minimum. The > RFC I am planning on proposing will have only the bare minimum because > it's the least controversial part and is the most useful. The other > stuff we can debate about later.
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