include/AD/automata/lrpardrv.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 LR1_parser_driver_h
  26 #define LR1_parser_driver_h
  27
  28 #include <iostream.h>
  29 #include <AD/automata/lr1.h>   // LR driver basics
  30 #include <AD/contain/stack.h>  // generic stacks
  31
  32 //////////////////////////////////////////////////////////////////////////////
  33 //  Class LR1ParserDriver is used to implement a LR(1) style
  34 //  parser driver with automatic semantic stack manipulation.
  35 //  The class is parametrized with the type of the semantic stack
  36 //  element(the semantic stack is current implemented as an array).
  37 //
  38 //  We assume the user will derive a subclass using this driver
  39 //  as one of the superclass.  The following methods should be provided
  40 //  by the user:
  41 //
  42 //      Terminal get_token()  --- this method retrieved the next token
  43 //                                from the input stream.
  44 //      void     act (Action) --- this method should be used to execute
  45 //                                the semantic actions.
  46 //////////////////////////////////////////////////////////////////////////////
  47 template <class T>
  48    class LR1ParserDriver : public LR1 {
  49
  50       LR1ParserDriver(const LR1ParserDriver&);    // no copy constructor
  51       void operator = (const LR1ParserDriver&);   // no assignment
  52
  53    public:
  54
  55       ////////////////////////////////////////////////////////////////////////
  56       //  Make inherited types visible
  57       ////////////////////////////////////////////////////////////////////////
  58       typedef LR1                     Super;
  59       typedef Super::Symbol           Symbol;
  60       typedef Super::State            State;
  61       typedef Super::Offset           Offset;
  62       typedef Super::Rule             Rule;
  63       typedef Super::ProductionLength ProductionLength;
  64
  65    public:
  66
  67       ////////////////////////////////////////////////////////////////////////
  68       //  Constructor and destructor
  69       ////////////////////////////////////////////////////////////////////////
  70
  71       LR1ParserDriver( const Offset           base_table  [],
  72                        const State            check_table [],
  73                        const State            defact_table[],
  74                        const State            next_table  [],
  75                        const ProductionLength len_table   [],
  76                        const unsigned short   equiv_table []
  77                      );
  78
  79       virtual ~LR1ParserDriver();
  80
  81       ////////////////////////////////////////////////////////////////////////
  82       //  Parsing
  83       ////////////////////////////////////////////////////////////////////////
  84       virtual void parse ();
  85
  86    protected:
  87       ////////////////////////////////////////////////////////////////////////
  88       // Tokenizer (must be implemented in derived class)
  89       ////////////////////////////////////////////////////////////////////////
  90       virtual Terminal get_token() = 0;
  91
  92       ////////////////////////////////////////////////////////////////////////
  93       //  Others:
  94       //     open()  -- prelude routine, redefinable by client.
  95       //     close() -- post processing routine, redefinable by client.
  96       //     act()   -- action routine, redefinable by client.
  97       //     init_stack_size() -- stack size, redefinable by client.
  98       //                          Notice that the stack is automatically
  99       //                          adjusted by the driver.
 100       //     stack_overflow()  -- handler for stack overflow.
 101       ////////////////////////////////////////////////////////////////////////
 102       virtual void open  ()         {}
 103       virtual void close ()         {}
 104       virtual void act   (Action A) {}
 105       virtual int  init_stack_size() const { return 4096; }
 106       virtual void stack_overflow() {}
 107    };
 108
 109 ///////////////////////////////////////////////////////////////////////////////
 110 //  Parser driver for LR(1) style parser tables.
 111 ///////////////////////////////////////////////////////////////////////////////
 112 template <class T>
 113    void LR1ParserDriver::parse()
 114    {  int          size = init_stack_size();
 115       Stack<State> S(size);  // the parse stack
 116       Stack<T>     V(size);  // the semantic value stack
 117       Terminal     T;
 118
 119       open();              // prelude
 120       S.push(start_state); // push start state
 121       T = get_token();     // get next token
 122
 123       //
 124       // the parsing loop
 125       //
 126       for (;;) {
 127          State s = S.top();
 128          State n = go(s,T);
 129          if (isError(n)) {          // parse error
 130          } else if (isShift(n)) {   // shift action
 131             s = n; T = get_token();
 132          } else {                   // reduce action
 133             Rule r = reduceRule(n); // reduction rule
 134             act(r);                 // execute the action
 135             S.pop(reduceLen(r));    // pop the parse stack
 136             S.push(go(s = S.top(),T));
 137          }
 138       }
 139
 140       close(); // coda
 141    }
 142
 143 #endif