The ordering h < g < m is not possible, since if (g, h) had been added through a left-arc, then h would have been reduced, and if (g, h) and (h, m) were both added through register-stack arcs, then one of them would have violated the (R close , σ 1 ) / ∈ A or the (σ 1 , R f ar ) / ∈ A precondition.
similar reasoning can rule out m < g < h. Condition (b) of Definition 3 is also satisfied.