Re: [RFC] Using objects as keys

On Mon, 2014-10-27 at 00:41 -0700, Stas Malyshev wrote: > Hi! > > > Once your proposal is in the language, you will never, in the future, be > > able to add real support for objects as keys, because the semantics is > > blocked. > > This implies this support is not "real" and we want some other support. > I don't think I agree with either. > > > I do understand where your proposal is coming from and what it is trying > > to accomplish. But I think, at least, that it should clearly spell out > > that any ambition to really support objects as array keys in the base > > language, will then be given up. > > Was there ever such an ambition? Does somebody have any idea how to > properly do it and a reason why? > > > I hardly see how that would make sense. SplObjectStorate operates with > > object identity as determined by spl_object_hash, right? Changing that > > Now, it does, since there's no other option. However, in the future > there may be other options - i.e. objects whose identity is not the same > as their memory address. For example, for an object representing number > (GMP) or string (UString) their identity is their content, not their > memory address. Thus, if you want to use UString as an index, or have an > unique set of strings, spl_object_hash would not be your friend. > Of course, there's always an option of just telling it - e.g. by > providing an option to the ctor. > > > Right. Somehow python manages to live quite fine with that fact. > > For some definitions of "quite fine", I presume - I can't see how a > hashtable that repeatedly calls user code can be efficient. It probably > isn't. > > > Right. You don't do that when your object implements __hash__ and __eq__. > > Or, more precisely, you're asked nicely not to do it - because there's > no way to actually ensure it. > -- > Stanislav Malyshev, Software Architect > SugarCRM: http://www.sugarcrm.com/ > Morning, As already pointed out by Stas, using objects as array keys would require a rewrite of the HashTable API, something integral to PHP. I'm not sure that is realistic, or possible. I think probably, the best way we can support objects as collection keys is with the introduction of generics, something totally disconnected from this RFC, that nobody has a working patch for. Cheers Joe