Re[2]: Fwd: Re[2]: [PHP-DEV] PHP 8.1 enum con st expressions problem

>Пятница, 30 июля 2021, 16:45 +03:00 от Rowan Tommins ><rowan.collins@gmail.com>: >  >On 30/07/2021 13:20, Kirill Nesmeyanov wrote: >> But in addition to bit-masks, there are also at least cases of addition and subtraction >> (the most popular). Can't we adapt all math expressions existing in nature to specific cases, >> thereby building our own pseudo-AST? >> >> (Some::A + Some::B) * Some::C | Some::D; > >If you are performing arithmetic on a value, that value is not of an >enum type, or at least not in the way the current feature defines "enum". > >If you write an enum for days of the week, you might give them integer >values, such that "Day::MONDAY->value === 1" and "Day::SUNDAY->value === >7". However, expressions such as "Day::SATURDAY + Day::SUNDAY"  and >"Day::MONDAY * Day::TUESDAY" are clearly meaningless. > >At a stretch, a language with operator overloading might define >"Day::MONDAY + 1" to return "Day::TUESDAY", and "Day::MONDAY + 10" >to >either error or wrap around to "Day::THURSDAY"; but PHP has covered that >use case by allowing methods, e.g. "Day::MONDAY->advanceBy(10)", which >is more flexible and arguably more expressive. > >On the other hand, the expression "$weekend = Day::SATURDAY | >Day::SUNDAY" seems reasonable; but we don't need the result to be an >integer - it would have no meaning on its own - we just need to be able >to ask things like "is $today in $weekend?" Returning some kind of >EnumSet object means we retain the type information, and can keep our >values of 1 to 7 (or have no values at all) rather than having to use >powers of 2. > >Regards, > >-- >Rowan Tommins >[IMSoP] > >-- >PHP Internals - PHP Runtime Development Mailing List >To unsubscribe, visit: https://www.php.net/unsub.php   1) What about this example?   enum ErrorGroup: int {     case NOTICE = 0;     case WARNING = 10;     case ERROR = 20; }   enum ErrorCode: int {     case UNKNOWN = 0;          case A = ErrorGroup::NOTICE + 1;     case B = ErrorGroup::NOTICE + 2;     case С = ErrorGroup::NOTICE + 3;     case D = ErrorGroup::WARNING + 1;     case E = ErrorGroup::ERROR + 1; }   The same applies to, for example, designing Http statuses (However, since they are pre-specified, this does not make sense).   2) OR: As an example from real life, I can show this pseudo-enum: https://github.com/SerafimArts/ffi-sdl/blob/master/src/Kernel/Video/PixelFormat.php     How is this supposed to work in the future? Bit masks are just one case of many others.   -- Kirill Nesmeyanov