So I came across the concept of UNUMs on the Pony language mailing list 
<http://lists.ponylang.org/pipermail/ponydev/2015-July/000071.html> this 
morning. I hadn't heard of them before, and a quick search doesn't show up 
anything on this mailing list, so I guess most people here haven't either. 
They're a proposed alternate encoding for numbers by John L. Gustafson. 
This presentation by him sums it up nicely:

http://sites.ieee.org/scv-cs/files/2013/03/Right-SizingPrecision1.pdf

“Unums”(universal numbers) are to floating point what floating point is to 
> fixed point.
> Floating-point values self-describe their scale factor, but fix the 
> exponent and fraction size. Unums self-describe the exponent size, fraction 
> size, and inexact state, and include fixed point and IEEE floats as special 
> cases.
>

The presentation can be seen here, provided you have the Silverlight plugin:

http://sites.ieee.org/scv-cs/archives/right-sizing-precision-to-save-energy-power-and-storage

Now, I don't know enough about this topic to say if they're a good or bad 
idea, but I figured the idea is interesting/relevant enough to share with 
the Julia crowd.

I'm also wondering if they could be implemented (relatively) easily within 
Julia, given its flexible type system. If so, they might provide an 
interesting advanced example, no?

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