4 ms·

If that is the only use case I would rather want another solution to keep the language minimal. Just like the garbage collection was moved to a library.

by jeltz 13y ago

dbaupp 13y ago
I think that the core team thought about this long and hard, but it was decided that there was no other solution. A virtual method call to look up some property shared by all the DOM nodes was just too expensive: a constant offset field look up is far far faster.
pcwalton 13y ago
Can't really do it. I tried. The type checker just plain has to know about inheritance for it to work and be safe. The good news is that's an extremely constrained sort of inheritance, very unlike traditional OO in that it doesn't have base classes--it's just a special extension to the trait (typeclass) system that allows you to require that structs begin with a certain set of fields. In fact, I don't even call it inheritance these days--I prefer the name "structural constraints".
- thirsteh 13y ago
  I think this is a good idea. It seems similar to Go's embedding: http://golang.org/doc/effective_go.html#embedding http://golang.org/doc/effective_go.html#embedding
  - pcwalton 13y ago
    The difference is that the base struct can call methods on the derived struct, whereas this is not possible with that kind of struct embedding. This is important for some use cases (e.g. the DOM or the render tree).
    - thirsteh 13y ago
      I see.
- carterschonwald 13y ago
  ooh, is this like record subtyping? Have you seen ermine https://github.com/ermine-language https://github.com/ermine-language or Ur/web? http://www.impredicative.com/ur/ http://www.impredicative.com/ur/ [edit, on #rust it was explained to me that its only for pointers to structs, but thats fine by me]
  - dbaupp 13y ago
    If anyone is interested, the proposal for Rust is detailed in http://smallcultfollowing.com/babysteps/blog/2013/10/24/single-inheritance/ http://smallcultfollowing.com/babysteps/blog/2013/10/24/sing...
- jeltz 13y ago
  Thanks for the answer, and I think I like your solution to the problem.

If that is the only use case I would rather want another solution to keep the language minimal. Just like the garbage collection was moved to a library.

by jeltz 13y ago

If that is the only use case I would rather want another solution to keep the language minimal. Just like the garbage collection was moved to a library.

dbaupp 13y ago

I think that the core team thought about this long and hard, but it was decided that there was no other solution. A virtual method call to look up some property shared by all the DOM nodes was just too expensive: a constant offset field look up is far far faster.

pcwalton 13y ago

Can't really do it. I tried. The type checker just plain has to know about inheritance for it to work and be safe. The good news is that's an extremely constrained sort of inheritance, very unlike traditional OO in that it doesn't have base classes--it's just a special extension to the trait (typeclass) system that allows you to require that structs begin with a certain set of fields. In fact, I don't even call it inheritance these days--I prefer the name "structural constraints".

thirsteh 13y ago
I think this is a good idea. It seems similar to Go's embedding: http://golang.org/doc/effective_go.html#embedding http://golang.org/doc/effective_go.html#embedding
- pcwalton 13y ago
  The difference is that the base struct can call methods on the derived struct, whereas this is not possible with that kind of struct embedding. This is important for some use cases (e.g. the DOM or the render tree).
  - thirsteh 13y ago
    I see.
carterschonwald 13y ago
ooh, is this like record subtyping? Have you seen ermine https://github.com/ermine-language https://github.com/ermine-language or Ur/web? http://www.impredicative.com/ur/ http://www.impredicative.com/ur/ [edit, on #rust it was explained to me that its only for pointers to structs, but thats fine by me]
- dbaupp 13y ago
  If anyone is interested, the proposal for Rust is detailed in http://smallcultfollowing.com/babysteps/blog/2013/10/24/single-inheritance/ http://smallcultfollowing.com/babysteps/blog/2013/10/24/sing...
jeltz 13y ago
Thanks for the answer, and I think I like your solution to the problem.