Implement the "unum" representation in D ?

[Andrei Alexandrescu via Digitalmars-d]

On 7/16/15 9:49 PM, Nick B wrote:
> On Monday, 13 July 2015 at 21:25:12 UTC, Per Nordlöw wrote:
>
>> Can we do anything useful with unums in numeric algorithms if only
>> have forward or bidirectional access? Similar to algorithms such as
>> Levenshtein that are compatible with UTF-8 and UTF-16, Andrei? :)
>
> Question for Andrei, above, if he would like to reply.

Haven't gotten to reading about unum, so I'm a bit lost. Who has 
forward/bidirectional access? -- Andrei