Pascal-recursion combination enumerator:
let rec choose k xs =
if k = 0 then [[]]
else match xs with
| [] -> []
| h :: rest ->
List.map (fun c -> h :: c) (choose (k - 1) rest)
@ choose k rest
C(9, 4) = |choose 4 [1; ...; 9]| = 126
Tests pure-functional enumeration with List.map + closure over h,
@ append, [] | h :: rest pattern match on shrinking input.
200 baseline programs total -- milestone.
giles
fad81e0b0c