class T()
    method a(); write("This is T's a"); end
end

class S: T()
    method a(); write("This is S's a"); end
end

procedure main()
    write("S:",deepcopy(S()).a())
end

procedure deepcopy(A, cache)  #: return a deepcopy of A
    local k

    /cache := table()        # used to handle multireferenced objects
    if \cache[A] then return cache[A]

    case type(A) of {
        "table"|"list": {
            cache[A] := copy(A)
            every cache[A][k := key(A)] := deepcopy(A[k], cache)
            }
        "set": {
            cache[A] := set()
            every insert(cache[A], deepcopy(!A, cache))
            }
        default: {           # records and objects (encoded as records)
            cache[A] := copy(A)
            if match("record ",image(A)) then {
                every cache[A][k := key(A)] := deepcopy(A[k], cache)
                }
            }
        }
    return .cache[A]
end