[Ocaml-lib-devel] List.map_pairs

[Richard J. <ri...@an...>]

On the subject of new list functions, how about:

let rec list_map_pairs f = function
  | [] | [_] -> invalid_arg "list_map_pairs"
  | [x; y] -> [f x y]
  | x :: (y :: _ as xs) ->
      f x y :: list_map_pairs f xs

We use this sort of pattern to disaggregate data which has been
collected using an incrementing counter - something like this:

# let xs = [ 0; 1; 4; 5; 5; 5; 8; 9; 9; 10 ];;
val xs : int list = [0; 1; 4; 5; 5; 5; 8; 9; 9; 10]
# list_map_pairs (fun a b -> b - a) xs;;
- : int list = [1; 3; 1; 0; 0; 3; 1; 0; 1]

Rich.

-- 
Richard Jones, CTO Merjis Ltd.
Merjis - web marketing and technology - http://merjis.com
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