On Thu, Jul 3, 2014 at 9:45 AM, Stefan Karpinski <ste...@karpinski.org> wrote:
> On Thu, Jul 3, 2014 at 9:42 AM, Ivar Nesje <iva...@gmail.com> wrote: > >> We should really create a simple system where you can get those hints >> printed in the REPL, without defining more methods. > > > Yes, I think we should really pursue this avenue. > > For what it's worth – and perhaps something since I'm the original > perpetrator of the str*str concatenation syntax – I've come to regret this > operator choice. My reasoning at this point is that we want our operators > to have fairly "pure" meanings. I chose str*str because concatenation can > be viewed as a kind of multiplication in the ring of string patterns > (alternation in the regex sense is the addition operation, the empty string > is the unit and the non-matching pattern is the zero). However, many > operations can be viewed as a form of multiplication. In the max-plus > algebra <http://en.wikipedia.org/wiki/Max-plus_algebra>, for example, > addition is the multiplication operator. So, at this point I think we > should stick to very pure classical meanings for operators in Base – the > Base.* function should be just addition of numbers in the classical sense, > not the broader sense of addition in any conceivable ring. > Hi! I would add "minimal" and "intuitive". I agree '*' is an unfortunate choice for a string concat op, but I don't see a problem with '+' - mathematics routinely overloads symbols, and I don't see any strictly mathematical reason to privilege commutativity as an essential component of the meaning of '+'. Commutativity is an add-on that comes after the more primitive sense of accumulation, which is what concatenation is. You can't build a brick wall from the top down. I think its a pretty safe bet that nobody would ever be tempted to think "ab" + "cd" = "cd" + "ab", ditto for "++". On the other hand, if you want to minimize overloading, an alternative notation (my fav), used by Z and ML, among other languages, is '^'; since that's already taken, maybe '^^'. In any case, str * str isn't all that tragic; think of it as a beauty mark, a flaw that makes the whole face more beautify. ;) -Gregg Reynolds
