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Earlier quoted context omitted.
It also makes multiple inheritance (which Rust has, through Java-like interfaces) easy to implement, and fast at runtime. The virtual inheritance of C++ is a real mess, by contrast [1]. [1]: http://www.phpcompiler.org/articles/virtualinheritance.html Edit: I don't mean to bash C++ here, BTW; the skinny-pointer approach has a lot of benefits when all you need is single inheritance (and there are early-stage proposals…
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Great article. The main bit of new information for me was that while Rust supports dynamic dispatch, its implementation has a noticeable difference from C++. In C++, the vtable pointer is in the object itself. In Rust, it's stored inside what is essentially a "fat pointer." Pointers to traits ("trait objects") are actually two pointers: the pointer to the vtable and the pointer to the actual object. This seems to hav…
This is also how Go does it. It looks like Rust traits can do everything Go interfaces can do, and more?
You revert to the OOP-style vtables if existential quantification is introduced because you have to pack code with the data, rather than being able to inline the data from a statically known index of methods into the concrete call-sites.
As it stands, I'm more likely to want Clean-style uniqueness typing in Haskell for a non-GC'd life-cycle for memory than I am to use Rust, but it's nice to see what we can accomplish with linear types baked into the compiler. Wish regions hadn't been abandoned, but it seems like somebody wanted Rust pushed into becoming a product quickly.
Typeclasses benefit from the same "zero runtime overhead" in Haskell (but not Scala). This is particularly important in non-strict languages where inlining is a more prominent aspect of making code performant. Fortunately, GHC is a lot easier to understand WRT optimizations than gcc. You revert to the OOP-style vtables if existential quantification is introduced because you have to pack code with the data, rather tha…
Typeclasses benefit from the same "zero runtime overhead" in Haskell (but not Scala). This is particularly important in non-strict languages where inlining is a more prominent aspect of making code performant. Fortunately, GHC is a lot easier to understand WRT optimizations than gcc. You revert to the OOP-style vtables if existential quantification is introduced because you have to pack code with the data, rather tha…
Typeclasses benefit from the same "zero runtime overhead" in Haskell (but not Scala). This is particularly important in non-strict languages where inlining is a more prominent aspect of making code performant. Fortunately, GHC is a lot easier to understand WRT optimizations than gcc. You revert to the OOP-style vtables if existential quantification is introduced because you have to pack code with the data, rather tha…
Haskell type classes can not be implemented with zero runtime overhead in all cases, because it is possible to have an unbounded number of instances at runtime for a single type class. The Rust equivalent will just fail at compile time (of the trait implementation, not the trait definition) due to a recursion error.
Great article. The main bit of new information for me was that while Rust supports dynamic dispatch, its implementation has a noticeable difference from C++. In C++, the vtable pointer is in the object itself. In Rust, it's stored inside what is essentially a "fat pointer." Pointers to traits ("trait objects") are actually two pointers: the pointer to the vtable and the pointer to the actual object. This seems to hav…
Great article. The main bit of new information for me was that while Rust supports dynamic dispatch, its implementation has a noticeable difference from C++. In C++, the vtable pointer is in the object itself. In Rust, it's stored inside what is essentially a "fat pointer." Pointers to traits ("trait objects") are actually two pointers: the pointer to the vtable and the pointer to the actual object. This seems to hav…
This is also how interfaces are implemented in Go.
So why not use "interface" keyword?