// 
// alternation_reachable.pp
// 
// computes the alternation reachable sets for each vertex in the class
// dictionary and returns an Ar_Vertex_list.  An Ar_Vertex contains the 
// name of the Vertex in question, the alternation reachable set in question
// and the 'contained-in' member used in determining if the list of 
// alternation reachable sets correspond to a class dictionary that satisfies
// the tree property.
// 
// compute_ar_sets initializes the return list (this includes generating the
// list of all the vertices and setting the alternation reachable sets for
// construction vertices) then calls ar_compute to do the rest of the
// computing.
// 
// ar_compute visits each vertex in the list, computing the alternation
// reachable sets for any vertex that it hasn't been calculated for already.
// This is done for improved performance since the calculated value of 
// alternation reachable sets for alternation vertices is the union of the
// values of the alternation reachable sets for all the vertices that the
// alternation vertex in question has alternation edges going to.
// 

// init, call main computation 
*operation* Ar_Vertex_list* compute_ar_sets()
  *init* (@ init_ar_list() @)
  *traverse* *from* Cd_graph *to-stop* Cd_graph
  *wrapper* Cd_graph
    *prefix* (@ 
      return_val->ar_compute(this); 
    @)

// visit each vertex and calculate if not done already
*operation* void ar_compute(Cd_graph* cd)
  *traverse* *from* Ar_Vertex_list *to* Ar_Vertex
  *wrapper* Ar_Vertex
    *prefix* (@ 
      if (ar == NULL) {
        ar = cd->ar_compute(v);
      } 
    @)  

// init routine, set up names, handle construction vertices
*operation* Ar_Vertex_list* init_ar_list()
  *init* (@ new Ar_Vertex_list @)
  *traverse* *from* Cd_graph
             *to-stop*  Adjacency
  *wrapper* Adjacency
    *suffix*  (@ Ar_Vertex* ar_v = new Ar_Vertex(source, NULL, NULL);
                 return_val->append(ar_v); @)

// compute the ar set for a particular vertex
*operation* Vertex_comma_list* ar_compute(Vertex* v)
  *init* (@ new Vertex_comma_list @)
  *traverse* *from* Cd_graph *to-stop* Adjacency
  *carry* *in* Cd_graph* cd = (@ this @)
    *along* *from* Cd_graph *to* Adjacency
  *wrapper* Adjacency
    *suffix* (@ if (v->g_equal(source)) {
                  return_val->concatenate(ar_vertices(cd)); 
                } @)


*operation* Vertex_comma_list* ar_vertices(Cd_graph* cd)
  *init* (@ new Vertex_comma_list @)
  *traverse* *merge* (*from* Adjacency *to-stop* Construct_ns,
                      *from* Adjacency *through* ->*,alternat_ns,* 
                             *to-stop* Vertex)
  *carry* *in* Vertex* src = (@ source @)
    *along* *from* Adjacency *to* Construct_ns
  *wrapper* Construct_ns
    *suffix* (@ return_val->set_union(src); @)
  *wrapper* Vertex
    *suffix* (@ return_val->set_union(cd->ar_compute(this)); @)