If so, I had no idea. However, if it doesn't come in before 1.0 then I fear that ecosystem will develop around not having one and then by 2.0 it will be "too late"
On Tue, Apr 30, 2013 at 10:49 AM, Gábor Lehel <illiss...@gmail.com> wrote: > On Tue, Apr 30, 2013 at 6:57 PM, Tim Chevalier <catamorph...@gmail.com>wrote: > >> On Mon, Apr 29, 2013 at 9:30 PM, Erik S <sw...@earthling.net> wrote: >> > On 4/29/2013 2:00 PM, Graydon Hoare wrote: >> >> Yes. Formalizing and completing the definition of the constant >> >> expression subgrammar would be extremely valuable. It's one of the >> >> major high-risk areas remaining the the design space. -Graydon >> > VHDL is a very different language from Rust (it's a hardware design >> > language, not a normal programming language), but it has the nicest >> > constant system I've worked with. >> > >> > The rule is basically that constant expressions can contain: >> > >> > Literals (i.e. 5, 0x20) >> > Expressions that depend on constants (i.e. 0x5 + 10 * const_k) >> > Any "pure" function whose arguments are constant. (i.e. 5 + f_pure(5, >> > const_k) ) >> > >> > It's this last rule that is truly beautiful. You can use the same >> > functions in both constant initialization and run-time code, with only >> > the requirement that they are pure. Pure functions are ones whose output >> > depends only on their arguments (and constants). Allowing functions to >> > initialize constants avoids the whole annoyance in C/C++ where you have >> > to use macros to make things compile-time const. It also allows a >> > surprising amount of compile-time optimization. >> > >> > I don't know how realistic this is for constants in a language like rust >> > - but it would be very elegant if it could work. >> > >> >> We used to have a notion of pure functions in Rust, but that was >> removed recently. It originally existed for typestate (a feature we >> removed a while ago) and more recently to assist the borrow checker. >> We removed it because in Rust, it was impractical to define an >> easily-checkable pure subset of the language. Bringing it back in is >> somewhat less likely than adding significant whitespace. >> >> Cheers, >> Tim >> > > I thought an effects system (encompassing purity) is something that was > vaguely planned for 2.0? > > >> >> >> >> -- >> Tim Chevalier * http://catamorphism.org/ * Often in error, never in doubt >> "Too much to carry, too much to let go >> Time goes fast, learning goes slow." -- Bruce Cockburn >> _______________________________________________ >> Rust-dev mailing list >> Rust-dev@mozilla.org >> https://mail.mozilla.org/listinfo/rust-dev >> > > > > -- > Your ship was destroyed in a monadic eruption. > _______________________________________________ > Rust-dev mailing list > Rust-dev@mozilla.org > https://mail.mozilla.org/listinfo/rust-dev > >
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