
<<--File: SetImpl.mesa>>
<<Last Edited by: CSChow, January 28, 1985 2:34:40 am PST>>
    <<Preas, August 2, 1986 8:15:49 pm PDT>>

DIRECTORY
List,
Set;

SetImpl: CEDAR PROGRAM
IMPORTS List
EXPORTS Set = BEGIN OPEN Set;


    New: PUBLIC PROC [] RETURNS [Handle] ={
        RETURN [NEW[HandleRec _ [NIL]]]
        }; --Create


    Put: PUBLIC PROC[han: Handle, e: REF ANY] RETURNS [BOOL] ={
        IF ~List.Memb[e, han.elements] THEN han.elements _ CONS[e, han.elements];
        RETURN[~List.Memb[e, han.elements]]
        };-- Put


    Enumerate: PUBLIC PROC[han: Handle, action: EachEltAction] RETURNS [stop: BOOL _ FALSE] ={
    FOR list: LIST OF REF ANY _ han.elements, list.rest UNTIL stop OR list = NIL DO
    stop _ action[list.first]
    ENDLOOP;
        };--Enumerate

    Cardinality: PUBLIC PROC[han: Handle] RETURNS [NAT] ={
        RETURN [NAT [List.Length[han.elements]]]
        };--Cardinality

    Nth: PUBLIC PROC[han: Handle, n: NAT] RETURNS [REF ANY] ={
        RETURN [List.NthElement[han.elements, n]]
        };--Nth

    Difference: PUBLIC PROC[han1, han2: Handle] RETURNS [Handle] ={
        RETURN [NEW[HandleRec _ [List.ListDifference[han1.elements, han2.elements]]]]
        };--Difference

    Remove: PUBLIC PROC[han: Handle, e: REF ANY] RETURNS [BOOL] ={
        val: BOOL _ List.Memb[e, han.elements];
        han.elements _ List.Remove[e, han.elements];
        RETURN [val]
        };--Remove

    In: PUBLIC PROC[han: Handle, e: REF ANY] RETURNS [BOOL] ={
        RETURN [List.Memb[e, han.elements]]
        };--In

    END.