I'd also be interested in a kind of "reverse" argument - *if* we had this added, what are the costs? There are arguments of "no, pure/robot ninja is enough" - fine, we're not taking those away so you aren't required to use singleton But what is the *downside* of having singleton? [...]
A similar argument comes up with basically every extension, and it is a very weak one. Code is mainly *read*, not written, so the less you need to know to read and understand code, the better it is. Lots of different ways to do the same thing makes programs harder to understand, and you ultimately end up with Perl. :-} And if we take this argument seriously, we should probably add "doubleton" (synonym for "replicate 2"), "tripleton" (synonym for "replicate 3"), etc., too. Hey, you don't have to use it after all, we're not taking away "replicate"...