%cfa_seq(From, To)
%cfa_payload(X, Node, Path)

    %EXTERNAL CALL
    %constraints: fn's entry/final scope does not have prev/next scopes resp.
:- cfa_seq_guarded(_, NodeTo, in(_)); cfa_seq(_, NodeTo).
:- cfa_seq_guarded(NodeFrom, _, out(_)); cfa_seq(NodeFrom, _).

cfa_payload(P, NodeTo, (Guard, Path)):-
  cfa_payload(P, NodeFrom, Path);
  cfa_seq_guarded(NodeFrom, NodeTo, in(Guard)).
  
weak(cfa_payload(P, NodeTo, (Guard, Path))):-
  weak(cfa_payload(P, NodeFrom, Path));
  cfa_seq_guarded(NodeFrom, NodeTo, in(Guard)).  

  %Path collapse
cfa_payload(P, Node, Path):-   
   cfa_payload(P, NodeFrom, Path) : cfa_seq_guarded(NodeFrom, Node, in(_));
   cfa_payload(P, Node, (_, Path));
   cfa_seq_guarded(_, Node, in(_)).
  
    %EXTERNAL RET
cfa_payload(P, NodeTo, Path2):-
  cfa_payload(P, NodeFrom, Path); Path = (Guard, Path2);
  cfa_seq_guarded(NodeFrom, NodeTo, out(Guard)).
  
cfa_payload(P, NodeTo, ()):-
  cfa_payload(P, NodeFrom, ());
  cfa_seq_guarded(NodeFrom, NodeTo, out(_)).
  
weak(cfa_payload(P, NodeTo, Path2)):-
  weak(cfa_payload(P, NodeFrom, Path)); Path = (Guard, Path2);
  cfa_seq_guarded(NodeFrom, NodeTo, out(Guard)).  
  
    %INTERNAL
weak(cfa_payload(P, Node, Path)):-
  weak(cfa_payload(P, NodeFrom, Path));
  cfa_seq(NodeFrom, Node).
  
    %INTERNAL AND  
cfa_payload(P, Node, Path):-
  cfa_payload(P, NodeFrom, Path);
  cfa_seq(NodeFrom, Node); Node = and(_).

  
    %INTERNAL OR
weak(cfa_payload(P, Node, Path)):-
  cfa_payload(P, NodeFrom, Path);
  cfa_seq(NodeFrom, Node); Node = or(_).
  
cfa_payload(P, Node, Path):-  
  cfa_payload(P, NodeFrom, Path) : cfa_seq(NodeFrom, Node); 
  Node = or(_);
  cfa_seq(N, Node); cfa_payload(P, N, Path).  
  
    %INTERNAL EMPTY
    %INTERNAL SCOPE
:- cfa_seq(A, empty(X)); cfa_seq(B, empty(X)); A<>B.
:- cfa_seq(A, scope(X)); cfa_seq(B, scope(X)); A<>B.

cfa_payload(P, Node, Path):-
  cfa_payload(P, NodeFrom, Path);
  cfa_seq(NodeFrom, Node); Node = empty(_).

cfa_payload(P, Node, Path):-
  cfa_payload(P, NodeFrom, Path);
  cfa_seq(NodeFrom, Node); Node = scope(_).