eqBox (Q _ ps (a,(x,b)),s) (Q _ ps' (a',(x',b')),s')
      | ps == ps' =
          do eqBox (a,s) (a',s')
             eq (x,Boxed (b,s)) (x',Boxed (b',s'))
eqBox (Q _ ps (a,(x,b)),s) (Q _ ps' (a',(x',b')),s')
      | ps == ps' =
          do eqBox (a,s) (a',s')
             eq (x,Boxed (b,s)) (x',Boxed (b',s'))
eqBox (Q _ ps (a,(x,b)),s) (Q _ ps' (a',(x',b')),s')
      | ps == ps' =
          do eqBox (a,s) (a',s')
             eq (x,Boxed (b,s)) (x',Boxed (b',s'))