Kinds of containers

[Nordlöw via Digitalmars-d]

On Wednesday, 21 October 2015 at 11:05:12 UTC, Andrei 
Alexandrescu wrote:
> Andrei

Exiting, times ahead!

One thing that has caught my attention lately:

I believe one way of making `std.experimental.allocator` usage 
(more) automatic is to add subtypes of containers for specific 
limited access patterns.

For instance, some graph algorithms, such a calculating subgraphs,

for instance: 
https://github.com/nordlow/justd/blob/master/knet/setops.d#L10

internally uses hashsets (currently implemented as a bool[Value])

for instance: 
https://github.com/nordlow/justd/blob/master/knet/setops.d#L15

only require the two primitives:

- bool insert(Value value): returns true if value was stored, not 
already existed
- bool contains(Value value)

In this case (when no references are leaked), `HashSet` could be 
sub-typed to, say `ExpandableConstantHashSet`, which can @safely 
and automatically make use of a `RegionAllocator` for 
super-performance.

In this way, even complete beginners in D, could @safely use 
Phobos containers to beat C++ performance.

Destroy!