Implement typeclasses analogous to Fractional and AsFractional for discardable fractions
I think it would make sense to have a library analogous to fractional for discardable fractions. I think it needs to say
Φ (p ⋅ q) ⊣⊢ Φ p ∗ Φ q like for fractions (using dfrac composition) and also perhaps
Persistent (Φ DfracDiscarded).