I like the new definition of fixed point. Its quite crisp.
Building on the definition we can now argue that any integer number representation is: integer value/2^N
With N being a positive integer. N=0 is basically a regular INT, and N>0 is a fixed point number.
If we accept this definition we can ask ourselves how 13.2 and 13.3 fit into our new definition. This as both are built on the assumption that N=1, which goes against our more open-ended definition.
Arguably, 13.3 is just short hand for a vmul followed by vnclip.
Similarly, 13.2 is just short hand for vadd/vsub followed by vssra.
Utilizing this more crisp definition we can now semantically define fixed point math operations as:
vmul of SEW*SEW -> 2xSEW [N.(SEW-N) -> 2N.2(SEW-N)]
vssra of 2xSEW -> 2xSEW >> needed guarding for the expected math operation
vadd of guarded 2xSEW with guarded running sum vector
vnclip of guarded running sum vector 2xSEW >> SEW-guard bits+N to convert back to N.(SEW-N)
#or if we want to utilize a 2N.2(SEW-N) double precision fixed point
#note this construct is currently not feasible
#vnclip_shift_left guarded 2xSEW << guard bits