Re: [Caml-list] recursion/iterator question

[Jon Harrop <jon@ffconsultancy.com>]

On Monday 17 April 2006 10:36, Christian Stork wrote:
> Or, if you choose to represent triplets as lists of three elements, you can
> generalize Jon's solution to
>
>   let rec combs = function
>
>       | (0, _) -> [[]]
>       | (n, es) when n > List.length es -> []
>       | (n, e::es) -> List.map (fun l -> e::l) (combs (n-1, es)) @ combs
>       | (n, es)
>
>   let triplets es = combs (3, es)
>
> Question to the rest of the list:  The ocaml compiler complains with
>   ...
>   Warning P: this pattern-matching is not exhaustive.
>   Here is an example of a value that is not matched:
>   (1, [])
>   (However, some guarded clause may match this value.)
>   ...
>
> Am I right to assume there's no way to get rid of this warning short of
> disabling P-warnings on the command line?  (I can't list all the lacking
> patterns since they depend on n, right?)

The lacking patterns are covered by (_, []), so you probably want:

  | 0, _ | _, [] -> [[]]

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
Objective CAML for Scientists
http://www.ffconsultancy.com/products/ocaml_for_scientists