Re: [Caml-list] sharing problem ...

[Pietro Abate <Pietro.Abate@anu.edu.au>]

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Tnx for you comments. My example was wrong as Damien pointed out
because sets are immutable and I was using them in a very wrong way.
I got around the problem using an object with a mutable val. I don't
think this is the best solution but I couldn't figure out how to do it
with using simple records...

attacched there is the code snippet...

tnx.

p


On Mon, Jan 26, 2004 at 02:27:46PM +0100, Damien Doligez wrote:
> If you really need mutable sets, maybe you should use the Hashtbl
> module instead of Set.

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module MyMap = Map.Make(
    struct
        type t = string
        let compare = compare 
    end)

module MySet = Set.Make(
    struct
        type t = int
        let compare = compare
    end)

class set t =
    object
        val mutable value = MySet.empty
        val shared = t
        method shared = shared
        
        method copy = {<>}
            
        method add_list tl =
            value <-
                List.fold_left (
                    fun set term -> MySet.add term set
            ) value tl
            
        method print =
            if shared then print_string "(shared) : "
            else print_string ":";
            print_string "[";
            MySet.iter (
                fun e ->
                    print_int e;
                    print_string ";"
                ) value;
            print_endline "]"
    end
    
class mystruct l =
    object(self)
        initializer List.iter (fun (s,t) -> self#add_name ~t:t s ) l
        
        val mutable sets = MyMap.empty

        method add_name ?(t=false) name=
            if not(MyMap.mem name sets) then
                sets <- MyMap.add name (new set t) sets
            else ()
        
        method copy =
            let map_copy m =
                MyMap.fold (
                    fun k s m ->
                        if s#shared then MyMap.add k s m
                        else MyMap.add k s#copy m
                ) m MyMap.empty 
        in {< sets = map_copy (sets) >}

        method add_elem name tl =
            try
                let set = MyMap.find name sets in
                set#add_list tl;
                (* sets <- MyMap.remove name sets;
                sets <- MyMap.add name set sets *)
            with Not_found ->
                Printf.printf "%s : " name;
                failwith "My not declared"

        method print =
            MyMap.iter (
                fun k s ->
                    print_string k;
                    s#print
            ) sets

end

let a1 = new mystruct ["a",true;"b",false] ;;

let _ =
    a1#add_elem "a" [1;2;3];
    a1#add_elem "b" [1;2;3];
    print_endline "a1: ";
    a1#print;
    print_newline ();;

let a2 = a1#copy;;

let _ =
    a2#add_elem "a" [4;5];
    a2#add_elem "b" [4;5];
    print_endline "a2: ";
    a2#print;
    print_newline ();
    print_endline "a1: ";
    a1#print;
    print_newline ();
    a1#add_elem "a" [6];
    print_endline "a2: ";
    a2#print;
    print_endline "a1: ";
    a1#print;
    print_newline ();;