Ever since D emerged from the primordial soup back in the Paleozoic Era, there's been discussion around here about array appending and the need/want for a capacity field. To solve this problem, Andrei's pre-release Phobos includes an array appender struct (see http://www.erdani.dreamhosters.com/d/web/phobos/std_array.html). While this gets the job done, IMHO it feels kind of hackish and undermining of builtin arrays, especially now that D supports alias this.
When alias this came out (yes, this was just last week but it feels like forever ago with the pace of evolution lately), I started playing around with the idea that an ArrayAppender!(T) should consist of an extremely thin wrapper around a T[]. It should implicitly convert to T[] and be usable exactly like a T[], except that it should have a capacity field and its ~= operator should be overridden to use the capacity field for fast appends. IMHO this is a much more elegant solution than having an ArrayAppender that is a completely different animal than builtin arrays and doesn't allow access to the builtin array's operators without an explicit conversion. Right now, my prototype of the implicitly-converting ArrayAppender doesn't work well due to bugs 2777, 2778, and 2781, but if there's sufficient interest, I'd be willing to release the prototype anyhow for comment after it's cleaned up a little. What do others think? Should arrays w/ capacity fields blend in with and implicitly convert to builtin arrays, or should there be a high wall distinguishing the two?
