> I am not sure but I think that the negative a- in Sanskrit lengthens
before
> *(H)yewg-...
Normally (?invariably) the a- is short. But a:yunak with long a: has been
quoted - though I can't find a reference for it. Compounds also keep
the -a- short, eg as'va-yuj.
There is however hiatus in pra-ugam RV 1:35:5 ? < pra-Hyugam