include/AD/automata/follow.h

   1 //////////////////////////////////////////////////////////////////////////////
   2 // NOTICE:
   3 //
   4 // ADLib, Prop and their related set of tools and documentation are in the
   5 // public domain.   The author(s) of this software reserve no copyrights on
   6 // the source code and any code generated using the tools.  You are encouraged
   7 // to use ADLib and Prop to develop software, in both academic and commercial
   8 // settings, and are free to incorporate any part of ADLib and Prop into
   9 // your programs.
  10 //
  11 // Although you are under no obligation to do so, we strongly recommend that
  12 // you give away all software developed using our tools.
  13 //
  14 // We also ask that credit be given to us when ADLib and/or Prop are used in
  15 // your programs, and that this notice be preserved intact in all the source
  16 // code.
  17 //
  18 // This software is still under development and we welcome any suggestions
  19 // and help from the users.
  20 //
  21 // Allen Leung
  22 // 1994
  23 //////////////////////////////////////////////////////////////////////////////
  24
  25 #ifndef follow_set_computation_h
  26 #define follow_set_computation_h
  27
  28 #include <AD/automata/firstset.h>
  29 #include <AD/contain/bitset.h>
  30 #include <AD/memory/mempool.h>
  31
  32 //////////////////////////////////////////////////////////////////////////////
  33 //  This class computes the follow sets of a grammar.
  34 //  follow(A) = { c | such that c can immediately follow A in a derivation }
  35 //  Implicitly, we need to know compute first(X).  We'll inherit
  36 //  from class FirstSet.
  37 //////////////////////////////////////////////////////////////////////////////
  38 class FollowSet : public FirstSet {
  39
  40    FollowSet(const FollowSet&);        // no copy constructor
  41    void operator = (const FollowSet&); // no assignment
  42
  43 public:
  44
  45    ///////////////////////////////////////////////////////////////////////////
  46    //  Import some types
  47    ///////////////////////////////////////////////////////////////////////////
  48    typedef FirstSet              Super;
  49    typedef Super::Symbol         Symbol;
  50    typedef Super::Terminal       Terminal;
  51    typedef Super::NonTerminal    NonTerminal;
  52    typedef Super::Production     Production;
  53    typedef Super::ProductionList ProductionList;
  54
  55 protected:
  56
  57    ///////////////////////////////////////////////////////////////////////////
  58    //  Internals
  59    ///////////////////////////////////////////////////////////////////////////
  60    BitSet ** follow_set;  // an array of terminals set indexed by non-terminal
  61
  62 public:
  63
  64    ///////////////////////////////////////////////////////////////////////////
  65    //  Constructor and destructor
  66    ///////////////////////////////////////////////////////////////////////////
  67    FollowSet(const Grammar&, Mem&);
  68   ~FollowSet();
  69
  70    ///////////////////////////////////////////////////////////////////////////
  71    //  Follow set computation
  72    ///////////////////////////////////////////////////////////////////////////
  73    inline const BitSet& follow (NonTerminal A) const { return *follow_set[A]; }
  74 };
  75
  76 #endif