not passing around count any more

day3.ml

@@ -29,17 +29,17 @@ let read_cell map x y = (* return Some char at these coordinates, or None if bel
   then Some (List.nth (List.nth map x) (wrapped_y y map))
   else None
 
-let rec go map position slope count = (* move across the map, counting trees *)
+let rec go map position slope = (* move across the map, counting trees *)
   let (x, y) = position in
   let (dy, dx) = slope in (* suddenly regretting having x be the vertical axis.. *)
   match read_cell map x y with
-  | None -> count (* off the map. stop counting *)
-  | Some '#' -> go map (x+dx, y+dy) slope (count+1)
-  | Some a -> go map (x+dx, y+dy) slope count
+  | None -> 0 (* off the map! stop counting *)
+  | Some '#' -> 1 + go map (x+dx, y+dy) slope
+  | Some a -> go map (x+dx, y+dy) slope
 
 let map = read_file "day3.txt" |> List.map explode
 let slopes = [(1, 1); (3, 1); (5, 1); (7, 1); (1, 2)]
-let tree_counts = slopes |> List.map (fun slope -> go map (0, 0) slope 0);;
+let tree_counts = slopes |> List.map (fun slope -> go map (0, 0) slope);;
 
 List.iter (fun count -> Printf.printf "Number of trees: %i\n" count) tree_counts;;