Instance frequencySizeMonotonic_alt :
forall {A : Type} (g0 : G A) (lg : seq (nat * G A)),
SizeMonotonic g0 ->
lg \subset [set x | SizeMonotonic x.2 ] ->
SizeMonotonic (frequency g0 lg).

Lemma pickDrop_leq_top {A} (l : seq (nat * G (option A))) (n : nat) k g l' size s :
pickDrop l n = (k, g, l') ->
semGenSize g size (Some s) ->
n < sum_fst l.