Casting lemmas for non-negative rational numbers involving sums and products #
theorem NNRat.cast_multisetSum {K : Type u_2} [DivisionSemiring K] [CharZero K] (s : Multiset ℚ≥0) :
theorem NNRat.cast_sum {α : Type u_1} {K : Type u_2} [DivisionSemiring K] [CharZero K] (s : Finset α) (f : α → ℚ≥0) :