Implement the "unum" representation in D ?

["Nordlöw"]

> Also, because they are variable sized, you need to access them 
> through pointers if you want random access. Now you are reading 
> both the pointer and the value from memory.

We might not need random access though.

For basic linear algebra forward or bidirectional should be 
enough which should suit this format.

Depends on the application.