function PRE_fill_envelope_rhs(rhs)  return 0 end
function POST_fill_envelope_rhs(rhs) return 0 end
function PRE_fill_envelope_lhs(rhs)  return 0 end
function POST_fill_envelope_lhs(rhs) return 0 end

function PRE_fill_spec_rhs(rhs)  return 0 end
function POST_fill_spec_rhs(rhs) return 0 end
function PRE_fill_spec_lhs(rhs)  return 0 end
function POST_fill_spec_lhs(rhs) return 0 end