Re: "ocaml_beginners"::[] tail recursion

> On Monday 10 March 2008 17:49:06 stevewirts wrote:
>> could anyone tell me if this is tail recursive?
>>
>> let append l1 l2 =
>> let rl1 = List.rev l1 in
>>  let rec rappend l1 l2 =
>>       if l1 = [] then l2
>>       else
>>       let hd = List.hd l1 in
>>       let tl = List.tl l1 in
>>       let larger = hd :: l2 in
>>       rappend tl larger
>>   in rappend rl1 l2;;
>>
>> # append [1;2;3] [4;5;6];;
>> - : int list = [1; 2; 3; 4; 5; 6]
>
> That is tail recursive but you can write it much more elegantly using pattern
> matching:
>
>  let rec rev_append l1 l2 =
>    match l1, l2 with
>    | [], l2 -> l2
>    | hd::tl, l2 -> rev_append tl (hd::l2);;
>
>  let append l1 l2 =
>    rev_append (List.rev l1) l2;;