I don't use real pointers at all. Memory is stored in the global variable m, which is indexed by an uint32 (which I call k). My addresses are indexes. As the smallest bucket is 16 bytes, so the indexes are multiples of 4. So yes, in theory I could store 3 additional states (x+1, x+2, x+3), not even 2 bits. But I had to remove them everywhere...
Do you use these? What for?

https://github.com/ktye/i/blob/master/k.go#L47
The index i accesses m.k[i] which is a uint32. It stores type and array size. m.k[1+i] is refcount and m.k[2+i...] is the data.
The data is accessed by m.c[8+i] for chars, or m.f[1+i] for float64. m.c, m.k, m.f share the same memory but are simply recasts.
What I currently miss, is a sorted or unique flag.
But i do not see which kind of value is small enough to be store in there...

I was about to right a sixel image encoder: https://github.com/ktye/i/blob/master/k/six.k
The mandelbrot example runs very slowly. Maybe you have an idea.

But the last part is unfinished.
On that same topic: To implement run length encoding, what is the inverse of repeat? ?x

If I have a vector 1 2 2 2 1, I would like to have two results, The value and the number of repetitions. e.g. (1 2 1;1 3 1).
I can see that there are repetitions with =':x

I might have seen that before, I think you already pointed that out to me. But I forgot about it.
And do you have a faster version for the mandelbrot?
This is the go version, including the sixel part: https://github.com/ktye/i/blob/master/k/six.go

I use the while operator, but need to return the new state and the number of iterations. Maybe packing and unpacking makes it slow. Also you have to store the initial state.
If you increase w and h, it shows that it is too slow.