Exemplo n.º 1
0
        private void ValidateGrammar()
        {
            var createAst         = _grammar.FlagIsSet(LanguageFlags.CreateAst);
            var missingAstTypeSet = new NonTerminalSet();
            var invalidTransSet   = new NonTerminalSet();

            foreach (var nt in _grammarData.NonTerminals)
            {
                //Check that if CreateAst flag is set then AstNodeType or AstNodeCreator is assigned on all non-transient nodes.
                if (createAst && nt.AstNodeCreator == null && nt.AstNodeType == null && !nt.FlagIsSet(TermFlags.NoAstNode))
                {
                    missingAstTypeSet.Add(nt);
                }
                if (nt.FlagIsSet(TermFlags.IsTransient))
                {
                    //List non-terminals cannot be marked transient - otherwise there may be some ambiguities and inconsistencies
                    if (nt.FlagIsSet(TermFlags.IsList))
                    {
                        _language.Errors.Add(GrammarErrorLevel.Error, null, Resources.ErrListCannotBeTransient, nt.Name);
                    }
                    //Count number of non-punctuation child nodes in each production
                    foreach (var prod in nt.Productions)
                    {
                        if (CountNonPunctuationTerms(prod) > 1)
                        {
                            invalidTransSet.Add(nt);
                        }
                    }
                }//if transient
                //Validate error productions
                foreach (var prod in nt.Productions)
                {
                    if (prod.IsSet(ProductionFlags.IsError))
                    {
                        var lastTerm = prod.RValues[prod.RValues.Count - 1];
                        if (!(lastTerm is Terminal) || lastTerm == _grammar.SyntaxError)
                        {
                            _language.Errors.Add(GrammarErrorLevel.Warning, null, Resources.ErrLastTermOfErrorProd, nt.Name);
                        }
                        // "The last term of error production must be a terminal. NonTerminal: {0}"
                    } //foreach prod
                }
            }         //foreac nt

            if (missingAstTypeSet.Count > 0)
            {
                _language.Errors.Add(GrammarErrorLevel.Warning, null, Resources.ErrNodeTypeNotSetOn, missingAstTypeSet.ToString());
            }
            if (invalidTransSet.Count > 0)
            {
                _language.Errors.Add(GrammarErrorLevel.Error, null, Resources.ErrTransientNtMustHaveOneTerm, invalidTransSet.ToString());
            }
        }//method
Exemplo n.º 2
0
 private static void ComputeNonTerminalsNullability(GrammarData data)
 {
     var undecided = data.NonTerminals;
       while (undecided.Count > 0) {
     var newUndecided = new NonTerminalSet();
     foreach (NonTerminal nt in undecided)
       if (!ComputeNullability(nt))
     newUndecided.Add(nt);
     if (undecided.Count == newUndecided.Count) return;  //we didn't decide on any new, so we're done
     undecided = newUndecided;
       }//while
 }
Exemplo n.º 3
0
        }     //method

        private static void ComputeNonTerminalsNullability(GrammarData data)
        {
            var undecided = data.NonTerminals;

            while (undecided.Count > 0)
            {
                var newUndecided = new NonTerminalSet();
                foreach (NonTerminal nt in undecided)
                {
                    if (!ComputeNullability(nt))
                    {
                        newUndecided.Add(nt);
                    }
                }
                if (undecided.Count == newUndecided.Count)
                {
                    return;                                 //we didn't decide on any new, so we're done
                }
                undecided = newUndecided;
            }//while
        }
    /*
    Initial condition: we have state S with conflicts on lookaheads in Sc.Conflicts. 
     Each reduce item Ir in S has a set of lookahead sources Ir.ReducedLookaheadSources. 
     Our goal is to a create non-canonical state ncState with proper lookaheds, create jumps to this state 
     on jump lookaheads from S to ncState, remove these jump lookaheads from lookahead sets of reduce items 
     and replace them with non-canonical non-terminal lookaheads.
    1. Compute all jump lookaheads jL and non-canonical lookaheads ncL for state Sc. 
    2. Collect relevant lookahead sources in lkhSources set. For each lookahead source lkhSrc in all reduce items, 
       if lkhSrc.Current.Firsts includes a jump lookahead in jL, include it into lkhSources. 
    3. Collect item cores for non-canonical state into ncCores. For each production Prod in productions 
       of current non-terminal of all items in lkhSources, if Prod.Firsts contains a jump lookahead, then add initial LR0 item of Prod 
       to ncCores.
    4. Add to ncCores all shift items in state Sc that have Current term in jump lookaheads. We need to include 
       such shift items from original state into non-canonical state to allow proper resolution of shift-reduce
       conflicts. We let shift items in current state "compete" with possible reductions to non-canonical lookaheads 
       inside non-canonical state. 
    5. Create (or find existing) non-canonical state Sn from ncCores. 
    6. Assign lookbacks to items in ncState. For each item Src in lkhSources, for each production Prod 
       in Src.Current.Productions, if Prod.DirectFirsts contains jump lookahead, then: 
       find LR item I in Sn with I.Core == Prod.LR0Items[0]; do the following: I.Lookbacks.Add(Src.Transition).
    7. For state S for each reduce item I adjust I.Lookaheads:  remove jump lookaheads from I.Lookaheads, 
         and add those non-canonical lookaheads that are in I.AllLookaheads
*/
    //TODO: one thing to look at - see if all items in ncState should lead to reduce item in some state. 
    //     There may be items (most likely top ones, expansions of original reduced lookahead) that never get 
    //     to full reduce, because we switch back to canonical state on reduction of some "child" non-terminal and
    //     continue through canonical states from there. 
    //     So we don't need to generate target transition states for these items (unreachable states). 
    //     The main trouble is that unreachable state may introduce conflicts that in fact are never realized. 
    #endregion
    private void SwitchStateToNLalrLookaheads(ParserState state) {
      //1. Compute minimal (most expanded) non-canonical lookaheads that resolve all conflicts
      ComputeStateNonCanonicalLookaheads(state);
      var stateData = state.BuilderData;
      //2. Collect reduced lookahead sources and non-terminal lookaheads
      var lkhSources = new LRItemSet();
      var ntSet = new NonTerminalSet(); //All non-terminals in current positions of lkhSources
      foreach(var reduceItem in stateData.ReduceItems)
        foreach (var lkhSource in reduceItem.ReducedLookaheadSources) {
          var ntLkh = lkhSource.Core.Current as NonTerminal;
          if (ntLkh == null) continue; 
          if (!ntLkh.Firsts.Overlaps(stateData.JumpLookaheads))continue;
          lkhSources.Add(lkhSource);
          ntSet.Add(ntLkh); 
        }
      //2. Collect core set for non-canonical state
      var ncCoreSet = new LR0ItemSet();
      foreach(var ntLkh in ntSet) 
        foreach(var prod in ntLkh.Productions)
          if (prod.Firsts.Overlaps(stateData.JumpLookaheads))
            ncCoreSet.Add(prod.LR0Items[0]); 
      //4. Add shift items
      foreach (var shiftItem in stateData.ShiftItems)
        if (stateData.JumpLookaheads.Contains(shiftItem.Core.Current))
          ncCoreSet.Add(shiftItem.Core); 
      //5. Find or create non-canonical state
      var oldStateCount = Data.States.Count;
      var ncState = FindOrCreateState(ncCoreSet, "SN"); //if not found, state is created and added to state list and state hash
      bool ncStateIsNew = Data.States.Count > oldStateCount;
      stateData.JumpTarget = ncState; 
      //6. Setup appropriate lookbacks in items in ncState; 
      // first set lookbacks for items originated from lookaheads of reduce items in original state.
      foreach(var lkhSource in lkhSources) {
        var ntLkh = lkhSource.Core.Current as NonTerminal;
        foreach (var prod in ntLkh.Productions)
          if (prod.Firsts.Overlaps(stateData.JumpLookaheads)) {
            var ncItem = ncState.BuilderData.AllItems.FindByCore(prod.LR0Items[0]);
            ncItem.Lookbacks.Add(lkhSource.Transition);
          }//if 
      }//foreach lkhSource
      //Now items orginated from shift items in original state in step 4 above
      // just copy lookbacks
      foreach (var shiftItem in stateData.ShiftItems)
        if (stateData.JumpLookaheads.Contains(shiftItem.Core.Current)) {
          var ncItem = ncState.BuilderData.ShiftItems.FindByCore(shiftItem.Core);
          shiftItem.ShiftedItem = ncItem; 
          ncItem.Lookbacks.UnionWith(shiftItem.Lookbacks);
          if (ncItem.Transition != null)
          ncItem.Transition.Include(shiftItem.Transition.Includes);
        }
      PropagateLookbacksAndTransitionsThruShifts(ncState); 
      //7. Adjust reduce items lookaheads in original state
      foreach (var reduceItem in stateData.ReduceItems) {
        foreach(var jumpLkh in stateData.JumpLookaheads)
          if (reduceItem.Lookaheads.Contains(jumpLkh))
            reduceItem.Lookaheads.Remove(jumpLkh);
        foreach (var ncLkh in stateData.NonCanonicalLookaheads)
          if (reduceItem.AllLookaheads.Contains(ncLkh))
            reduceItem.Lookaheads.Add(ncLkh);
      }//foreach reduceItem
      // 8. Create jump action to non-canonical state, remove shifts on jump lookaheads
      state.JumpAction = ParserAction.CreateJump(ncState);
      foreach (var jumpTerm in state.BuilderData.JumpLookaheads)
        if (state.Actions.ContainsKey(jumpTerm))
          state.Actions.Remove(jumpTerm); 
      //9. Complete generating states
      state.BuilderData.Conflicts.ExceptWith(state.BuilderData.JumpLookaheads);
    }//method
Exemplo n.º 5
0
        private void ValidateGrammar()
        {
            var createAst = _grammar.LanguageFlags.IsSet(LanguageFlags.CreateAst);
              var missingAstTypeSet = new NonTerminalSet();
              var invalidTransSet = new NonTerminalSet();
              foreach(var nt in _grammarData.NonTerminals) {
            //Check that if CreateAst flag is set then AstNodeType or AstNodeCreator is assigned on all non-transient nodes.
            if(createAst && nt.AstNodeCreator == null && nt.AstNodeType == null && !nt.Flags.IsSet(TermFlags.NoAstNode))
              missingAstTypeSet.Add(nt);
            if(nt.Flags.IsSet(TermFlags.IsTransient)) {
              //List non-terminals cannot be marked transient - otherwise there may be some ambiguities and inconsistencies
              if (nt.Flags.IsSet(TermFlags.IsList))
            _language.Errors.Add(GrammarErrorLevel.Error, null, Resources.ErrListCannotBeTransient, nt.Name);
              //Count number of non-punctuation child nodes in each production
              foreach(var prod in nt.Productions)
            if (CountNonPunctuationTerms(prod) > 1) invalidTransSet.Add(nt);
            }//if transient
            //Validate error productions
            foreach(var prod in nt.Productions)
              if(prod.IsSet(ProductionFlags.IsError)) {
            var lastTerm = prod.RValues[prod.RValues.Count -1];
            if (!(lastTerm is Terminal) || lastTerm == _grammar.SyntaxError)
              _language.Errors.Add(GrammarErrorLevel.Warning, null, Resources.ErrLastTermOfErrorProd, nt.Name);
                // "The last term of error production must be a terminal. NonTerminal: {0}"
              }//foreach prod
              }//foreac nt

              if (missingAstTypeSet.Count > 0)
            _language.Errors.Add(GrammarErrorLevel.Warning, null, Resources.ErrNodeTypeNotSetOn, missingAstTypeSet.ToString());
              if (invalidTransSet.Count > 0)
            _language.Errors.Add(GrammarErrorLevel.Error, null, Resources.ErrTransientNtMustHaveOneTerm,invalidTransSet.ToString());
        }
Exemplo n.º 6
0
        /*
         * Initial condition: we have state S with conflicts on lookaheads in Sc.Conflicts.
         * Each reduce item Ir in S has a set of lookahead sources Ir.ReducedLookaheadSources.
         * Our goal is to a create non-canonical state ncState with proper lookaheds, create jumps to this state
         * on jump lookaheads from S to ncState, remove these jump lookaheads from lookahead sets of reduce items
         * and replace them with non-canonical non-terminal lookaheads.
         * 1. Compute all jump lookaheads jL and non-canonical lookaheads ncL for state Sc.
         * 2. Collect relevant lookahead sources in lkhSources set. For each lookahead source lkhSrc in all reduce items,
         * if lkhSrc.Current.Firsts includes a jump lookahead in jL, include it into lkhSources.
         * 3. Collect item cores for non-canonical state into ncCores. For each production Prod in productions
         * of current non-terminal of all items in lkhSources, if Prod.Firsts contains a jump lookahead, then add initial LR0 item of Prod
         * to ncCores.
         * 4. Add to ncCores all shift items in state Sc that have Current term in jump lookaheads. We need to include
         * such shift items from original state into non-canonical state to allow proper resolution of shift-reduce
         * conflicts. We let shift items in current state "compete" with possible reductions to non-canonical lookaheads
         * inside non-canonical state.
         * 5. Create (or find existing) non-canonical state Sn from ncCores.
         * 6. Assign lookbacks to items in ncState. For each item Src in lkhSources, for each production Prod
         * in Src.Current.Productions, if Prod.DirectFirsts contains jump lookahead, then:
         * find LR item I in Sn with I.Core == Prod.LR0Items[0]; do the following: I.Lookbacks.Add(Src.Transition).
         * 7. For state S for each reduce item I adjust I.Lookaheads:  remove jump lookaheads from I.Lookaheads,
         *   and add those non-canonical lookaheads that are in I.AllLookaheads
         */
        //TODO: one thing to look at - see if all items in ncState should lead to reduce item in some state.
        //     There may be items (most likely top ones, expansions of original reduced lookahead) that never get
        //     to full reduce, because we switch back to canonical state on reduction of some "child" non-terminal and
        //     continue through canonical states from there.
        //     So we don't need to generate target transition states for these items (unreachable states).
        //     The main trouble is that unreachable state may introduce conflicts that in fact are never realized.
        #endregion
        private void SwitchStateToNLalrLookaheads(ParserState state)
        {
            //1. Compute minimal (most expanded) non-canonical lookaheads that resolve all conflicts
            ComputeStateNonCanonicalLookaheads(state);
            var stateData = state.BuilderData;
            //2. Collect reduced lookahead sources and non-terminal lookaheads
            var lkhSources = new LRItemSet();
            var ntSet      = new NonTerminalSet(); //All non-terminals in current positions of lkhSources

            foreach (var reduceItem in stateData.ReduceItems)
            {
                foreach (var lkhSource in reduceItem.ReducedLookaheadSources)
                {
                    var ntLkh = lkhSource.Core.Current as NonTerminal;
                    if (ntLkh == null)
                    {
                        continue;
                    }
                    if (!ntLkh.Firsts.Overlaps(stateData.JumpLookaheads))
                    {
                        continue;
                    }
                    lkhSources.Add(lkhSource);
                    ntSet.Add(ntLkh);
                }
            }
            //2. Collect core set for non-canonical state
            var ncCoreSet = new LR0ItemSet();

            foreach (var ntLkh in ntSet)
            {
                foreach (var prod in ntLkh.Productions)
                {
                    if (prod.Firsts.Overlaps(stateData.JumpLookaheads))
                    {
                        ncCoreSet.Add(prod.LR0Items[0]);
                    }
                }
            }
            //4. Add shift items
            foreach (var shiftItem in stateData.ShiftItems)
            {
                if (stateData.JumpLookaheads.Contains(shiftItem.Core.Current))
                {
                    ncCoreSet.Add(shiftItem.Core);
                }
            }
            //5. Find or create non-canonical state
            var  oldStateCount = Data.States.Count;
            var  ncState       = FindOrCreateState(ncCoreSet, "SN"); //if not found, state is created and added to state list and state hash
            bool ncStateIsNew  = Data.States.Count > oldStateCount;

            stateData.JumpTarget = ncState;
            //6. Setup appropriate lookbacks in items in ncState;
            // first set lookbacks for items originated from lookaheads of reduce items in original state.
            foreach (var lkhSource in lkhSources)
            {
                var ntLkh = lkhSource.Core.Current as NonTerminal;
                foreach (var prod in ntLkh.Productions)
                {
                    if (prod.Firsts.Overlaps(stateData.JumpLookaheads))
                    {
                        var ncItem = ncState.BuilderData.AllItems.FindByCore(prod.LR0Items[0]);
                        ncItem.Lookbacks.Add(lkhSource.Transition);
                    } //if
                }
            }         //foreach lkhSource
            //Now items orginated from shift items in original state in step 4 above
            // just copy lookbacks
            foreach (var shiftItem in stateData.ShiftItems)
            {
                if (stateData.JumpLookaheads.Contains(shiftItem.Core.Current))
                {
                    var ncItem = ncState.BuilderData.ShiftItems.FindByCore(shiftItem.Core);
                    shiftItem.ShiftedItem = ncItem;
                    ncItem.Lookbacks.UnionWith(shiftItem.Lookbacks);
                    if (ncItem.Transition != null)
                    {
                        ncItem.Transition.Include(shiftItem.Transition.Includes);
                    }
                }
            }
            PropagateLookbacksAndTransitionsThruShifts(ncState);
            //7. Adjust reduce items lookaheads in original state
            foreach (var reduceItem in stateData.ReduceItems)
            {
                foreach (var jumpLkh in stateData.JumpLookaheads)
                {
                    if (reduceItem.Lookaheads.Contains(jumpLkh))
                    {
                        reduceItem.Lookaheads.Remove(jumpLkh);
                    }
                }
                foreach (var ncLkh in stateData.NonCanonicalLookaheads)
                {
                    if (reduceItem.AllLookaheads.Contains(ncLkh))
                    {
                        reduceItem.Lookaheads.Add(ncLkh);
                    }
                }
            }//foreach reduceItem
            // 8. Create jump action to non-canonical state, remove shifts on jump lookaheads
            state.JumpAction = ParserAction.CreateJump(ncState);
            foreach (var jumpTerm in state.BuilderData.JumpLookaheads)
            {
                if (state.Actions.ContainsKey(jumpTerm))
                {
                    state.Actions.Remove(jumpTerm);
                }
            }
            //9. Complete generating states
            state.BuilderData.Conflicts.ExceptWith(state.BuilderData.JumpLookaheads);
        }//method