donkopotamus / rust Goto Github PK

Currently it feels like there is a slight inconsistency in std::slice between the following traits

• Vector - an object can provide a slice view into itself (as_slice).
• ImmutableVector - an object provides methods for slicing and dicing by integral index.
• MutableVector - an object provides both a slice view into itself (as_mut_slice) and methods for directly manipulating that object.

In practice, this means I can write a generic function fn needs_slice<T: Vector>(x: &T) that manipulate x only via its as_slice representation. Then I can easily declare that some new funky object can masquerade as a slice by simply implementing a single method.

• for example, if Option<T> implemented Vector (rather than its own as_slice) then I could pass one to needs_slice

In contrast, I can also write a function fn needs_mut_slice<T: MutableVector>(x: &T) that manipulates x only via its slice representation as_mut_slice. But I can't declare that some new funky object can masquerade as a mutable slice without adding a bunch of other methods that I don't actually want exposed on that object ... all I really want to do is implement just as_mut_slice.

So it feels like there should be four traits:

• SliceAccessor - an object can provide a slice view into itself (as_slice)
• MutableSliceAccessor - an object can provide a mutable slice view into itself (as_mut_slice)
• ImmutableVector - an object provides a large number of methods for slicing and dicing itself.
• MutableVector - an object provides methods for directly manipulating the object.