On Mon, Jul 27, 2009 at 10:58 AM, Andrei Alexandrescu<seewebsiteforem...@erdani.org> wrote: > Bill Baxter wrote: >> >> The requirement to add the post-blit is a little annoying. If a >> ValueContainer is made fundamental and it is built initially out of >> components with value semantics, then no explicit post-blit will be >> necessary. However if you go the other way and start with a >> RefContainer then a post-blit will be necessary when you implement the >> ValueContainer based on it. So to me it seems a little better to go >> with the ValueContainer as the base implementation. > > I think it's a matter of the most frequent use. I used to be a staunch > supporter of values for containers, until Walter revealed to me that in STL > you have value containers to constantly worry about adding the "&" > everywhere. Implicitly copying containers is 95% of cases an error in C++ > code. Witness all that advice about pass by reference etc. So why make that > the default, one might ask? Better go with the flow and make the default > case the easy case (reference), and if someone does want a value, have them > write Value!Container.
Hmm. Yeh, when passing containers around, 95% or more probably should be by ref. However when creating composite objects I'd say the percentage of time you want by ref is much lower. But I guess even then, by-ref composition isn't necessarily bad (as most VM languages show). --bb
