lib-src/automata/ll1gen.cc

   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 #include <iostream>
  26 #include <string.h>
  27 #include <AD/automata/ll1gen.h>   // LL(1) parser generator
  28 #include <AD/automata/follow.h>   // Follow set computation
  29 #include <AD/memory/mempool.h>    // Memory pool
  30
  31 /////////////////////////////////////////////////////////////////////////
  32 //  Constructor and destructor
  33 /////////////////////////////////////////////////////////////////////////
  34 LL1Gen::LL1Gen()  {} // nothing to add
  35 LL1Gen::~LL1Gen() {} // nothing to add
  36
  37 /////////////////////////////////////////////////////////////////////////
  38 //  Entry point of the compiler
  39 /////////////////////////////////////////////////////////////////////////
  40 void LL1Gen::compile(const Grammar& G)
  41 {
  42    MemPool     mem(4096);  // memory pool
  43    FollowSet   F(G,mem);   // compute the follow set
  44
  45    //////////////////////////////////////////////////////////////////////
  46    // Allocate the dfa tables
  47    //////////////////////////////////////////////////////////////////////
  48    create_tables( G.number_of_terminals() * 3, G.number_of_non_terminals(),
  49                   G.min_terminal(), G.max_terminal() );
  50
  51    //////////////////////////////////////////////////////////////////////
  52    // Allocate a mapping from non-terminals A to sets of terminals
  53    // that A predicts.
  54    //////////////////////////////////////////////////////////////////////
  55    BitSet ** predict_set = new BitSet * [ G.max_non_terminal() + 1 ];
  56    {  for (Symbol A = G.min_non_terminal(); A <= G.max_non_terminal(); A++) {
  57          predict_set[A] = new (mem, G.max_terminal() + 1) BitSet;
  58       }
  59    }
  60
  61    //////////////////////////////////////////////////////////////////////
  62    //  Allocate temporary buffers
  63    //////////////////////////////////////////////////////////////////////
  64    Symbol * symbols = new Symbol [ G.number_of_terminals() ];
  65    State  * delta   = new State  [ G.number_of_terminals() ];
  66    //int fan_out;          // fan out of a state
  67
  68    //////////////////////////////////////////////////////////////////////
  69    // Now compute the predict sets.
  70    //
  71    // predict(A -> XYZ) = first(XYZ) if ! nullable(XYZ)
  72    //                     first(XYZ) U follow(A) if nullable(XYZ)
  73    // predict_set(A) = U predict(A->XYZ)
  74    //////////////////////////////////////////////////////////////////////
  75    BitSet * predict = new (mem, G.max_terminal() + 1) BitSet;
  76    {  for (int i = 0; i < G.size(); i++) {
  77          Symbol     A = G.lhs(i);
  78          Production P = G.rhs(i);
  79          predict->clear();
  80          if (F.first(*predict,P)) predict->Union(F.follow(A));
  81       }
  82    }
  83
  84    //////////////////////////////////////////////////////////////////////
  85    //  Compute the states
  86    //////////////////////////////////////////////////////////////////////
  87
  88    //////////////////////////////////////////////////////////////////////
  89    //  Clean up properly
  90    //////////////////////////////////////////////////////////////////////
  91    delete [] symbols;
  92    delete [] delta;
  93    delete [] predict_set;
  94 }
  95
  96 /////////////////////////////////////////////////////////////////////////
  97 // Code emitter
  98 /////////////////////////////////////////////////////////////////////////
  99 std::ostream& LL1Gen::gen_code (std::ostream& out, const char name[]) const
 100 {  return Super::gen_code(out,name);
 101 }