Once fn()'s should consume their environment, perhaps it should be simply "self", where Self is non-copyable, so it gets moved out?
On Nov 30, 2013, at 4:21 PM, Patrick Walton <pwal...@mozilla.com> wrote: It's also not clear to me how "&once fn" can decompose into a trait in the future. The goal in the future is to make "fn()" a type of trait, to allow for C++-like zero-indirection closures. The different types of functions that we have today correspond to different "self" parameters: "|A|->B" corresponds to "&mut self" and "proc()" corresponds to "~self". But I don't see where "&once fn" fits in. Perhaps the right thing is to gate "&once fn" on by-value anonymous closures. I think once functions may be able to be made to work as function trait bounds. But implementing "&once fn" right now seems to close off our ability to have closures with the same efficiency as C++11 in the future, unless there's something I'm missing. Patrick Patrick Walton <pcwal...@mozilla.com> wrote: > > On 11/30/13 12:04 PM, Oren Ben-Kiki wrote: > >> Just to mention in passing - there's a related principle that converting >> a block to a closure shouldn't change its semantics. This obviously >> doesn't fully work because of return/break/continue; that said, if a >> block without such flow control constructs is wrapped into a closure, >> you'd expect it to just work. It doesn't, because to work it would have >> to be a once-called-stack-allocated lambda, which Rust doesn't have (I >> don't get the reason for that either :-) > > > If you decompose into a lambda plus the tupled set of upvars which it's > moving out of, then this respects TCP. > > Patrick > > ------------------------------ > > Rust-dev mailing list > Rust-dev@mozilla.org > https://mail.mozilla.org/listinfo/rust-dev > > -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. _______________________________________________ Rust-dev mailing list Rust-dev@mozilla.org https://mail.mozilla.org/listinfo/rust-dev
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