On Fri, Nov 8, 2013 at 6:06 PM, Igor Bukanov <i...@mir2.org> wrote: > On 8 November 2013 23:10, Oren Ben-Kiki <o...@ben-kiki.org> wrote: > > Yes, the down side is another level of indirection. This could be > optimized > > away for &'static str, but not for &str. Good point. > > The level of indirection comes from passing strings as &str, not just > as a plain str. But this raises the question. For immutable values > implementing &T parameter as T should not be observable from the safe > code, right? If so why not to declare that &T as a parameter is not a > pointer but rather a hint to use the fastest way to pass an instance > of T to the function. Then one can use &str as a parameter without any > performance impact due to indirection even if str itself is > fixed-sized 3-word block pointing to the heap allocated data. >
The only way you could avoid pointer indirection is by making the element length part of the type, like fixed-size vectors. For strings, there's not really a clearly meaningful element length (bytes? code points? graphemes?). An alternate vector/string doing small string optimization makes more sense to me.
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