if instances for absorbing, affine and persistent
I added instances of the form
Global Instance if_persistent P Q (b: bool) : Persistent P -> Persistent Q -> Persistent (if b then P else Q).
for Absorbing
, Affine
and Persistent
.
I only had to use the Persistent
one in a development I worked on, but I figured the other instances might be useful too, so I added them.