def add_symbolic_constraints(namespace):
    """ Add constraints to a namespace that are LinearExpressions of basic
    constraints.

    """
    bottom = namespace.bottom
    left = namespace.left
    width = namespace.layout_width
    height = namespace.layout_height
    namespace.right = left + width
    namespace.top = bottom + height
    namespace.h_center = left + width / 2.0
    namespace.v_center = bottom + height / 2.0
