Version française
Home     About     Download     Resources     Contact us    

This site is updated infrequently. For up-to-date information, please visit the new OCaml website at

Browse thread
[Caml-list] Subclasses and pattern matching
[ Home ] [ Index: by date | by threads ]
[ Search: ]

[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
Date: -- (:)
From: katre <katre@h...>
Subject: [Caml-list] Subclasses and pattern matching
Hello again!

I'm working on a project where I want to create a list of data, which is
all similar but not identical.  In other languages with which I am
familiar, I would do this with a base class and a few subclasses, as

class virtual abstractClass = 

    method virtual to_string : unit -> string

class subclass1 = 
    inherit abstractClass

    method thing () = "subclass1 thing"
    method to_string () = "subclass 1"

class subclass2 = 
    inherit abstractClass

    method thing2 () = "subclass2 thing"
    method to_string () = "subclass 2"

And I would create the list as

let l = [ (new subclass1 :> abstractClass); (new subclass :> abstractClass); (new subclass1 :> abstractClass); (new subclass2 :> abstractClass) ];

This seems to work fine.

However, I want to use pattern matching to go over this list.  I'm not
sure how this would work in ocaml.  My ideal function would look
something like this:

let rec show_list l =
    match l with
        [] -> ()
        | (h ofclass subclass1)::t -> print_string (h#thing()); show_list t
        | (h ofclass subclass2)::t -> print_string (h#thing2()); show_list t
        | (h ofclass abstractClass)::t -> print_string ("Unknown object " ^ (h#to_string())); show_list t

Is this possible?  What would the syntax be?


To unsubscribe, mail Archives:
Bug reports: FAQ:
Beginner's list: