R: filtering by list(s) of strings and returning all results that start with the content of the lists

let findnegative(d:int list list) =
  d
  |> List.map (fun x -> x |> List.filter (fun y -> y < 0))
  |> List.collect id

let findeven (t:float list list) = 
  t
  |> List.map (fun x -> x |> List.filter (fun y -> y % 2.0 = 0.0))
  |> List.collect id
  |> List.map int

let findnegative =
  List.collect <| List.filter ((>)0)

let findeven = 
  List.collect <| List.filter (fun x -> x % 2. = 0.) >> List.map int

[[p+s for s in suffixes] for p in prefixes]
#[['t1_price', 't1_sales'], ['t0_price', 't0_sales']]

arguments = itertools.product(list_of_values_for_arg_1, list_of_values_for_arg_2, ..., list_of_values_for_arg_n)
# or
arguments = itertools.product(*list_of_lists)
for arg in arguments:
    result=func(*arg)

{arg: func(*arg) for arg in itertools.product(*list_of_lists)}

f.writerow(list)

 λ> 
 λ> myFilter = filter (\[ls1, ls2] -> (7 > (length ls1 + length ls2)))
 λ> 
 λ> myFilter  [["aaa", "bbbb"],["c", "dd"]]
 [["c","dd"]]
 λ>