ToGFAD[exp] converts all occurring propagator types (FAD, SFAD, CFAD) to GFADs. This is mainly useful when doing expansions in kinematic invariants, where e.g. scalar products may not be appear explicitly when using FAD- or SFAD-notation.
ToGFAD is the inverse operation to FromGFAD.
Overview, GFAD, SFAD, CFAD, FeynAmpDenominatorExplicit, FromGFAD
ToGFAD[FAD[p]]\frac{1}{(p^2+i \eta )}
ToGFAD[FAD[p]] // StandardForm
(*FeynAmpDenominator[GenericPropagatorDenominator[Pair[Momentum[p, D], Momentum[p, D]], {1, 1}]]*)ToGFAD[SFAD[{p + q, m^2}]]\frac{1}{(-m^2+p^2+2 (p\cdot q)+q^2+i \eta )}
ToGFAD[SFAD[{p + q, m^2}]] // StandardForm
(*FeynAmpDenominator[GenericPropagatorDenominator[-m^2 + Pair[Momentum[p, D], Momentum[p, D]] + 2 Pair[Momentum[p, D], Momentum[q, D]] + Pair[Momentum[q, D], Momentum[q, D]], {1, 1}]]*)ToGFAD[SFAD[{p + q, m^2}], FinalSubstitutions -> {SPD[q] -> 0}]\frac{1}{(-m^2+p^2+2 (p\cdot q)+i \eta )}
ToGFAD[SFAD[{p + q, m^2}], FinalSubstitutions -> {SPD[q] -> 0}] // StandardForm
(*FeynAmpDenominator[GenericPropagatorDenominator[-m^2 + Pair[Momentum[p, D], Momentum[p, D]] + 2 Pair[Momentum[p, D], Momentum[q, D]], {1, 1}]]*)