def d_(member, readable=True, writable=True, final=True):
    """ Mark an Atom member as bindable from Enaml syntax.

    Parameters
    ----------
    member : Member
        The atom member to mark as bindable from Enaml syntax.

    readable : bool, optional
        Whether the member is readable from Enaml syntax. The member
        must be readable to use the '>>', ':=', and '::' operators.
        The default is True.

    writable : bool, optional
        Whether the member is writable from Enaml syntax. The member
        must be writable to use the '=', '<<', and ':=' operators.
        The default is True.

    final : bool, optional
        Whether or not the member can be redefined from Enaml syntax
        using the 'attr' keyword. The default is True and indicates
        that the member cannot be overridden.

    """
    metadata = member.metadata
    if metadata is None:
        metadata = member.metadata = {}
    metadata['d_member'] = True
    metadata['d_readable'] = readable
    metadata['d_writable'] = writable
    metadata['d_final'] = final
    return member