Empty array literals

[Michael Rynn]

> That IS what Walter thinks, actually. It's being moved to libraries
> (which is why there have been some nasty AA regressions in the past few
> compiler releases :-( ).

Sounds good. So the  source is in druntime?
Does that mean I can find out how to implement opIn ?.

I found the file druntime/src/rt/aaA.d 

The code looks nice, and its got a function _aaIn, which "Determine if 
key is in aa".

I want to implement opIn for my own class, but I have not found an 
example.

This week I have made a RadixTree implementation, for immutable array 
keys based on char or ubyte only. Values no such restriction.

I measured its lookups can be ~20x faster than AA equivalent.
Insertions somewhat slower than AA, even with a node preallocation heap 
for speedup.

I am sure I read about a radix tree in the past, but have not seen an 
implementation in current libraries.  It would be nice to have one, if 
only to stop me or others wasting time doing another. If its simple 
enough for me to make, there should be one there already.

I took a pretty recursive Java implementation (because I was supposed to 
be studying java) and reworked it.

So although AA are "in the library", there is not yet an obvious facility 
to completely replace the AA implementation with another equivalent (or 
even same) using non- druntime code and the facilities of struct, 
operator overrides etc.  

Whats the magic hook that will connect D source AA type operator "in"  to 
a class or struct function of a Tree, AA or trie?  Is there any great 
advantage to the AA being struct rather than class based?

I might like to upload the radix tree implementation, to see how it can 
be improved.

Thanks,
Michael R.