I did a little “code archaeology” in an attempt to elucidate what Rich may had been thinking:
In mid 2007, some of the persistent collection implementations had an EMPTY value defined. [1, 2]. (But, of course, no such EMPTY value was defined for MapEntrys.) Around a year later, MapEntrys were revised to participate in the vector abstraction [3]. A couple of months *after* this, “empty” was added to the collection abstraction [4], and usually implemented in terms of the EMPTY value, and MapEntry was made to return null. My analysis is inconclusive: Making MapEntry return null is logical, given that there is no EMPTY value to return. But, the MapEntry / vector business happening prior to this blurs the argument. Perhaps the real problem is that not all collections can be emptied, and thus thus empty shouldn't have been added to the collection abstraction. (ClojureScript separates out the idea, introducing IEmptyableCollection.) [1] https://github.com/clojure/clojure/commit/12457e7bf29747232bbfda2a0de3b72fbb14f3a9 [2] https://github.com/clojure/clojure/commit/4232de83a53e12741252d31aef9cecee5b8981da [3] https://github.com/clojure/clojure/commit/978af02b0a7e2b430c917b32b58215edcae2ad2d [4] https://github.com/clojure/clojure/commit/697b69fe9c8f5e2e8d40382e70d4ddd490c4a9ee -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
