Re: last item. no output

Matthieu Dubuget [email protected] [ocaml_beginners] schreef op 
18-10-2014 14:14:
> OK. Now you're problem is much clear.
>
> Have a close look at the type inferred for last.
>
> val last : 'a list list -> 'a list = <fun>
>
> This is due to your first match case: if your incoming list is void, you are returning a void list as last element.
>
> It has to return lists in the other cases. So does it.
>
> Which means that last is waiting for a list of list of something: 'a list list
>
>
> The problem is asking you to take a list of something ('a list), and return either that there is no last
> element (None) or that there is one element (Some something).
>
> val last: 'a list -> 'a option
>
> Have a look at what option is.
>
> Salutations
>

Thanks,

This one is working well :

let rec last list =
    match list with
    | [] -> None
    | [x] -> Some x
    | hd :: tl  -> last tl
    ;;


Roelof



------------------------------------

------------------------------------

Archives up to December 31, 2011 are also downloadable at http://www.connettivo.net/cntprojects/ocaml_beginners
The archives of the very official ocaml list (the seniors' one) can be found at http://caml.inria.fr
Attachments are banned and you're asked to be polite, avoid flames etc.
------------------------------------

Yahoo Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/ocaml_beginners/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/ocaml_beginners/join
    (Yahoo! ID required)

<*> To change settings via email:
    [email protected] 
    [email protected]

<*> To unsubscribe from this group, send an email to:
    [email protected]

<*> Your use of Yahoo Groups is subject to:
    https://info.yahoo.com/legal/us/yahoo/utos/terms/