[Caml-list] object single linked list - newbie

[Caml-list] object single linked list - newbie

[Ford Lissett]

I'm missing something really obvious here, please
explain -
 
line 13, characters 17-22:
This expression has type node node_type
It has no method get_link


type 't node_type = Class of 't | Nil;;

class node link_ =
object (self)
   val mutable link: node node_type = link_     
   
   method add node_ =
      let next = ref link in
      let peek = ref link in
      while (!peek != Nil) do
         next := !peek;
         peek := !next#get_link; (* line 13 *)
         done;
      link <- node_                       
                        
   method get_link = link
end;;

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Re: [Caml-list] object single linked list - newbie

[Alessandro Baretta]

Ford Lissett wrote:
> I'm missing something really obvious here, please
> explain -
>  
> line 13, characters 17-22:
> This expression has type node node_type
> It has no method get_link
> 
> 
> type 't node_type = Class of 't | Nil;;
> 

Type node node_type is not an object type, hence it cannot 
have methods. Type node is an object type and has method 
get_link. You must match against the Class constructor to 
get the object on which you want to invoke get_link.

>          peek := !next#get_link; (* line 13 *)

class node link_ =
object (self)
    val mutable link: node node_type = link_

    method add node_ =
       let next = ref link in
       let peek = ref link in
       while (!peek != Nil) do
          next := !peek;
          peek := match !next with
	   | Class(obj) -> obj#get_link
	   | Nil -> raise Not_found; (* line 13 *)
          done;
       link <- node_

    method get_link = link
end;;

Alex

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