Joel Falcou wrote:
On 09/03/11 19:14, Simonson, Lucanus J wrote:
This is a serious question that I'm posing with all humility. What benefit does proto provide in this case? What do we "get" for using it and what does it "cost". Can you sketch a comparison between an expression template operator+ on some concrete big int type both with and without use of Proto and walk us through how the use of proto is helpful and worthwhile? I can already reason that compile time with Proto will be higher than without, though I would be convinced by benchmarks to the contrary. We don't need concept checking in this case, so what does proto buy us? The fact that you dont have to maintain clunky and possibly inavsive ET core code. Writing the operator thingy to be all ET-enabled is a real mess and seriously, when you did it a couple of times by hand and did once with proto, you dont want to go back.
More over the cocnept of grammar and transform make your ET intent more clear. You can have multiples transform aimed at different pass inyou r ASt evalaution and have them cleanly separated fromt he main ET core code. transforms are also interchangeable and can be applied in a variety of context, support a nice and intutive recursive matching notation.
As for application, matching pattern of successive operators is a couple of lines in proto and is library agnostic. Writing a pattern matcher for arbitrary hand written ET code is not that trivial. For compile, it's always the saem. if you write crap proto it will be crap. All my proto based code has a non significant upfront compile overhead, and well, it comes from the preprocessing around and not proto itself.
Granted, proto has a number of very nice features. The question is, would xint benefit from them? Does this library require transforms and or multiple passes? I certainly hope not. The default operator precidence happens to the one we want in this case (as far as I understand) so what is the point of defining a grammar for operator expressions to achieve what would happen by default without one? Please correct me if I am wrong. Regards, Luke