Re: [Caml-list] Construct a list of records from several lists

[John Whitington <john@coherentgraphics.co.uk>]

Hi,

Casey Basichis wrote:
>
> Sorry about the confusion. I'm taking from one element from each list
> per record. The lists can all be arbitrarily long as long as they share
> the same length.
>
> lista = [1; 2; 3; 4; 5; 6; 3]
> listb = [2; 5; 7; 8; 1; 2; 4]
> listc = [4; 6; 8; 3; 5; 8; 2]
>
> type t = {a : int; b: int; c: int}
>
> {a=1; b=2; c=4}
> {a=2; b=5; c=6}
> {a=3; b=7; c=8}
> {a=4; b=8; c=3}

So with

type t = {a : int; b : int; c : int}

So you want a function of type

int list -> int list -> int list -> t list

I left a few blanks (* ... *) for you to fill in:

let build_record p q r =
   (* Put something here to build a single record *)

let rec records_from_lists la lb lc =
   match la, lb, lc with
   | [], [], [] ->
       (* And something here to deal with the base case *)
   | x::xs, y::ys, z::zs ->
       build_record x y z :: records_from_lists xs ys zs
   | _ ->
       (* And something here to deal with malformed inputs *)

If you need any more help, I suggest we move it to the beginners list...

With Thanks,

-- 
John Whitington
Director, Coherent Graphics Ltd
http://www.coherentpdf.com/