D 2.069.0 released, compiler automatically ported from C++ to D

Post by royjacobs » Wed, Nov 04, 2015, 1:05 PM UTC

johncolanduoni wrote: post #17

royjacobs wrote: post #9

Earlier quoted context omitted.

How would you consider Rust's generics as being part of a better C rather than a better C++?

I think it's more about Rust's approach to OO. In Rust, traits are usually used as interfaces for generics instead of dynamic dispatch. The generated code/performance is more like what you would get if you implemented them explicitly for each appropriate type in C, built around structs. You could do this with C++ templates, but it would be a huge pain in that language due to lack of template type safety. This is a qu…

Post by johncolanduoni » Wed, Nov 04, 2015, 1:12 PM UTC

royjacobs wrote: post #21

johncolanduoni wrote: post #17

Earlier quoted context omitted.

I think it's more about Rust's approach to OO. In Rust, traits are usually used as interfaces for generics instead of dynamic dispatch. The generated code/performance is more like what you would get if you implemented them explicitly for each appropriate type in C, built around structs. You could do this with C++ templates, but it would be a huge pain in that language due to lack of template type safety. This is a qu…

Hmm, I see your point, but I've found that even in template-heavy code the compiler can produce code that's pretty optimal. Are you saying that with Rust it is easier to fall into the pit of success, as it were -- requiring less reasoning about how a compiler might convert the [templated|generic] code optimally?

Post by rogeryu » Wed, Nov 04, 2015, 1:35 PM UTC

WalterBright wrote: post #2

Daniel Murphy is the man behind getting the sources converted from C++ to D. He wrote a program called "magicport" to do the bulk of it, with some manual tweaking. The back end is still in C++, showing that you can mix D and C++ code :-)

Post by srean » Wed, Nov 04, 2015, 1:43 PM UTC

logicchains wrote: post #6

amelius wrote: post #3

I'm wondering, is there an advantage of using D over Rust?

Some things D has that Rust doesn't: compiler-checked function purity annotations, higher-kinded types, variadic functions/generics, types parameterised by numbers, compile-time function evaluation, mixins, a fast compiler (the reference DMD compiler), powerful and convenient compile-time reflection (I think technically Rust can do anything D can at compile time, but it requires writing a syntax extension to do so).…

Post by srean » Wed, Nov 04, 2015, 1:56 PM UTC

johncolanduoni wrote: post #23

royjacobs wrote: post #21

Earlier quoted context omitted.

Hmm, I see your point, but I've found that even in template-heavy code the compiler can produce code that's pretty optimal. Are you saying that with Rust it is easier to fall into the pit of success, as it were -- requiring less reasoning about how a compiler might convert the [templated|generic] code optimally?

My point was not that Rust creates better template code, but that a lot of things one uses dynamic dispatch for in C++ use templates instead. There are plenty of times when one knows the full derived type of a class in C++, but one throws away that information virtual calls are used anyway. I think this is because Rust makes it far easier to use generics; they're type-safe and don't need to be pushed to header files.…