Making generalized Trie type in D

[Roman D. Boiko]

On Monday, 4 June 2012 at 22:22:34 UTC, Roman D. Boiko wrote:
> On Monday, 4 June 2012 at 22:06:49 UTC, Dmitry Olshansky wrote:
>> On 05.06.2012 1:56, Roman D. Boiko wrote:
>>> so range API doesn't fit that (but could with a tweak - 
>>> returning tail instead of mutating in popFront). If trie API 
>>> will have similar problems, then I need to invent my own. I 
>>> understand that immutability is not your priority for GSoC, 
>>> though.
>>
>> Well I might remove obstacles, if you outline your design more 
>> clearly.
> OK, thanks! I'll go through your code first to understand it 
> better. But even before that I need to finish an important 
> support request from my past customer...
Basically, the most important aspect of immutability is returning 
a new instance of data structure on each insert / delete / 
update, and keeping the old one unchanged, instead of performing 
update in-place. This may not fit your most common use cases, 
though. Would be great to enable such semantics via policies, but 
without deep analysis I can't come up with a good API / design 
for that (without overcomplicating it). Probably keeping mutable 
and immutable APIs separate is the best choice. Will return to 
this problem once I get a bit of free time.