production.cs

namespace CUP
{
	using System;
	
	/// <summary>This class represents a production in the grammar.  It contains
	/// a LHS non terminal, and an array of RHS symbols.  As various 
	/// transformations are done on the RHS of the production, it may shrink.
	/// As a result a separate length is always maintained to indicate how much
	/// of the RHS array is still valid.<p>
	/// 
	/// I addition to construction and manipulation operations, productions provide
	/// methods for factoring out actions (see  remove_embedded_actions()), for
	/// computing the nullability of the production (i.e., can it derive the empty
	/// string, see check_nullable()), and operations for computing its first
	/// set (i.e., the set of terminals that could appear at the beginning of some
	/// string derived from the production, see check_first_set()).
	/// 
	/// </summary>
	/// <seealso cref="     CUP.production_part
	/// "/>
	/// <seealso cref="     CUP.symbol_part
	/// "/>
	/// <seealso cref="     CUP.action_part
	/// "/>
	/// <version> last updated: 7/3/96
	/// </version>
	/// <author>  Frank Flannery
	/// 
	/// </author>
	
	public class production
	{
		private void  InitBlock()
		{
			_first_set = new terminal_set();
		}
		
		/*-----------------------------------------------------------*/
		/*--- Constructor(s) ----------------------------------------*/
		/*-----------------------------------------------------------*/
		
		/// <summary>Full constructor.  This constructor accepts a LHS non terminal,
		/// an array of RHS parts (including terminals, non terminals, and 
		/// actions), and a string for a final reduce action.   It does several
		/// manipulations in the process of  creating a production object.
		/// After some validity checking it translates labels that appear in
		/// actions into code for accessing objects on the runtime parse stack.
		/// It them merges adjacent actions if they appear and moves any trailing
		/// action into the final reduce actions string.  Next it removes any
		/// embedded actions by factoring them out with new action productions.  
		/// Finally it assigns a unique index to the production.<p>
		/// *
		/// Factoring out of actions is accomplished by creating new "hidden"
		/// non terminals.  For example if the production was originally: <pre>
		/// A ::= B {action} C D
		/// </pre>
		/// then it is factored into two productions:<pre>
		/// A ::= B X C D
		/// X ::= {action}
		/// </pre> 
		/// (where X is a unique new non terminal).  This has the effect of placing
		/// all actions at the end where they can be handled as part of a reduce by
		/// the parser.
		/// </summary>
		public production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l, string action_str)
		{
			InitBlock();
			int i;
			action_part tail_action;
			System.String declare_str;
			int rightlen = rhs_l;
			
			/* remember the length */
			if (rhs_l >= 0)
				_rhs_length = rhs_l;
			else if (rhs_parts != null)
				_rhs_length = rhs_parts.Length;
			else
				_rhs_length = 0;
			
			/* make sure we have a valid left-hand-side */
			if (lhs_sym == null)
				throw new internal_error("Attempt to construct a production with a null LHS");
			
			/* I'm not translating labels anymore, I'm adding code to declare
			labels as valid variables.  This way, the users code string is
			untouched 
			6/96 frankf */
			
			/* check if the last part of the right hand side is an action.  If
			it is, it won't be on the stack, so we don't want to count it 
			in the rightlen.  Then when we search down the stack for a
			Symbol, we don't try to search past action */
			
			if (rhs_l > 0)
			{
				if (rhs_parts[rhs_l - 1].is_action())
				{
					rightlen = rhs_l - 1;
				}
				else
				{
					rightlen = rhs_l;
				}
			}
			
			/* get the generated declaration code for the necessary labels. */
			declare_str = declare_labels(rhs_parts, rightlen, action_str);
			
			if (action_str == null)
				action_str = declare_str;
			else
				action_str = declare_str + action_str;
			
			/* count use of lhs */
			lhs_sym.note_use();
			
			/* create the part for left-hand-side */
			_lhs = new symbol_part(lhs_sym);
			
			/* merge adjacent actions (if any) */
			_rhs_length = merge_adjacent_actions(rhs_parts, _rhs_length);
			
			/* strip off any trailing action */
			tail_action = strip_trailing_action(rhs_parts, _rhs_length);
			if (tail_action != null)
				_rhs_length--;
			
			/* Why does this run through the right hand side happen
			over and over?  here a quick combination of two 
			prior runs plus one I wanted of my own
			frankf 6/25/96 */
			/* allocate and copy over the right-hand-side */
			/* count use of each rhs symbol */
			_rhs = new production_part[_rhs_length];
			 for (i = 0; i < _rhs_length; i++)
			{
				_rhs[i] = rhs_parts[i];
				if (!_rhs[i].is_action())
				{
					((symbol_part) _rhs[i]).the_symbol().note_use();
					if (((symbol_part) _rhs[i]).the_symbol() is terminal)
					{
						_rhs_prec = ((terminal) ((symbol_part) _rhs[i]).the_symbol()).precedence_num();
						_rhs_assoc = ((terminal) ((symbol_part) _rhs[i]).the_symbol()).precedence_side();
					}
				}
			}
			
			/*now action string is really declaration string, so put it in front!
			6/14/96 frankf */
			if (action_str == null)
				action_str = "";
			if (tail_action != null && tail_action.code_string() != null)
				action_str = action_str + "\t\t" + tail_action.code_string();
			
			/* stash the action */
			_action = new action_part(action_str);
			
			/* rewrite production to remove any embedded actions */
			remove_embedded_actions();
			
			/* assign an index */
			_index = next_index++;
			
			/* put us in the global collection of productions */
			SupportClass.PutElement(_all, _index, this);
			
			/* put us in the production list of the lhs non terminal */
			lhs_sym.add_production(this);
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Constructor with no action string. 
		/// </summary>
		public production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l):this(lhs_sym, rhs_parts, rhs_l, null)
		{
			InitBlock();
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/* Constructor with precedence and associativity of production
		contextually define */
		public production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l, string action_str, int prec_num, int prec_side):this(lhs_sym, rhs_parts, rhs_l, action_str)
		{
			InitBlock();
			
			/* set the precedence */
			set_precedence_num(prec_num);
			set_precedence_side(prec_side);
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/* Constructor w/ no action string and contextual precedence
		defined */
		public production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l, int prec_num, int prec_side):this(lhs_sym, rhs_parts, rhs_l, null)
		{
			InitBlock();
			/* set the precedence */
			set_precedence_num(prec_num);
			set_precedence_side(prec_side);
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/*-----------------------------------------------------------*/
		/*--- (Access to) Static (Class) Variables ------------------*/
		/*-----------------------------------------------------------*/
		
		
		/// <summary>Table of all productions.  Elements are stored using their index as 
		/// the key.
		/// </summary>
		protected internal static System.Collections.Hashtable _all = new System.Collections.Hashtable();
		
		/// <summary>Access to all productions. 
		/// </summary>
		public static System.Collections.IEnumerator all()
		{
			return _all.Values.GetEnumerator();
		}
		
		/// <summary>Lookup a production by index. 
		/// </summary>
		public static production find(int indx)
		{
			return (production) _all[indx];
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Total number of productions. 
		/// </summary>
		public static int number()
		{
			return _all.Count;
		}
		
		/// <summary>Static counter for assigning unique index numbers. 
		/// </summary>
		protected internal static int next_index;
		
		/*-----------------------------------------------------------*/
		/*--- (Access to) Instance Variables ------------------------*/
		/*-----------------------------------------------------------*/
		
		/// <summary>The left hand side non-terminal. 
		/// </summary>
		protected internal symbol_part _lhs;
		
		/// <summary>The left hand side non-terminal. 
		/// </summary>
		public virtual symbol_part lhs()
		{
			return _lhs;
		}
		
		
		/// <summary>The precedence of the rule 
		/// </summary>
		protected internal int _rhs_prec = - 1;
		protected internal int _rhs_assoc = - 1;
		
		/// <summary>Access to the precedence of the rule 
		/// </summary>
		public virtual int precedence_num()
		{
			return _rhs_prec;
		}
		public virtual int precedence_side()
		{
			return _rhs_assoc;
		}
		
		/// <summary>Setting the precedence of a rule 
		/// </summary>
		public virtual void  set_precedence_num(int prec_num)
		{
			_rhs_prec = prec_num;
		}
		public virtual void  set_precedence_side(int prec_side)
		{
			_rhs_assoc = prec_side;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>A collection of parts for the right hand side. 
		/// </summary>
		protected internal production_part[] _rhs;
		
		/// <summary>Access to the collection of parts for the right hand side. 
		/// </summary>
		public virtual production_part rhs(int indx)
		{
			if (indx >= 0 && indx < _rhs_length)
				return _rhs[indx];
			else
				throw new internal_error("Index out of range for right hand side of production");
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>How much of the right hand side array we are presently using. 
		/// </summary>
		protected internal int _rhs_length;
		
		/// <summary>How much of the right hand side array we are presently using. 
		/// </summary>
		public virtual int rhs_length()
		{
			return _rhs_length;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>An action_part containing code for the action to be performed when we 
		/// reduce with this production. 
		/// </summary>
		protected internal action_part _action;
		
		/// <summary>An action_part containing code for the action to be performed when we 
		/// reduce with this production. 
		/// </summary>
		public virtual action_part action()
		{
			return _action;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Index number of the production. 
		/// </summary>
		protected internal int _index;
		
		/// <summary>Index number of the production. 
		/// </summary>
		public virtual int index()
		{
			return _index;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Count of number of reductions using this production. 
		/// </summary>
		protected internal int _num_reductions = 0;
		
		/// <summary>Count of number of reductions using this production. 
		/// </summary>
		public virtual int num_reductions()
		{
			return _num_reductions;
		}
		
		/// <summary>Increment the count of reductions with this non-terminal 
		/// </summary>
		public virtual void  note_reduction_use()
		{
			_num_reductions++;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Is the nullability of the production known or unknown? 
		/// </summary>
		protected internal bool _nullable_known = false;
		
		/// <summary>Is the nullability of the production known or unknown? 
		/// </summary>
		public virtual bool nullable_known()
		{
			return _nullable_known;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Nullability of the production (can it derive the empty string). 
		/// </summary>
		protected internal bool _nullable = false;
		
		/// <summary>Nullability of the production (can it derive the empty string). 
		/// </summary>
		public virtual bool nullable()
		{
			return _nullable;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>First set of the production.  This is the set of terminals that 
		/// could appear at the front of some string derived from this production.
		/// </summary>
		//UPGRADE_NOTE: The initialization of  '_first_set' was moved to method 'InitBlock'. 'ms-help://MS.VSCC/commoner/redir/redirect.htm?keyword="jlca1005"'
		protected internal terminal_set _first_set;
		
		/// <summary>First set of the production.  This is the set of terminals that 
		/// could appear at the front of some string derived from this production.
		/// </summary>
		public virtual terminal_set first_set()
		{
			return _first_set;
		}
		
		/*-----------------------------------------------------------*/
		/*--- Static Methods ----------------------------------------*/
		/*-----------------------------------------------------------*/
		
		/// <summary>Determine if a given character can be a label id starter. 
		/// </summary>
		/// <param name="c">the character in question. 
		/// 
		/// </param>
		protected internal static bool is_id_start(char c)
		{
			return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c == '_');
			
			//later need to handle non-8-bit chars here
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Determine if a character can be in a label id. 
		/// </summary>
		/// <param name="c">the character in question.
		/// 
		/// </param>
		protected internal static bool is_id_char(char c)
		{
			return is_id_start(c) || (c >= '0' && c <= '9');
		}
		
		/*-----------------------------------------------------------*/
		/*--- General Methods ---------------------------------------*/
		/*-----------------------------------------------------------*/
		
		
		/// <summary>Return label declaration code
		/// </summary>
		/// <param name="labelname">   the label name
		/// </param>
		/// <param name="stack_type">  the stack type of label?
		/// </param>
		/// <author> frankf
		/// 
		/// </author>
		protected internal virtual string make_declaration(string labelname, string stack_type, int offset)
		{
			System.String ret;
			
			/* Put in the left/right value labels */
			if (emit.lr_values())
				ret = "\t\tint " + labelname + "left = ((CUP.runtime.Symbol)" + emit.pre("stack") + ".Peek(" + emit.pre("top") + "-" + offset + ")).left;\n" + "\t\tint " + labelname + "right = ((CUP.runtime.Symbol)" + emit.pre("stack") + ".Peek(" + emit.pre("top") + "-" + offset + ")).right;\n";
			else
				ret = "";
			
			/* otherwise, just declare label. */
			return ret + "\t\t" + stack_type + " " + labelname + " = (" + stack_type + ")((" + "CUP.runtime.Symbol) " + emit.pre("stack") + ".Peek(" + emit.pre("top") + "-" + offset + ")).Value;\n";
			
		}
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Declare label names as valid variables within the action string
		/// </summary>
		/// <param name="rhs">         array of RHS parts.
		/// </param>
		/// <param name="rhs_len">     how much of rhs to consider valid.
		/// </param>
		/// <param name="final_action">the final action string of the production. 
		/// </param>
		/// <param name="lhs_type">    the object type associated with the LHS symbol.
		/// 
		/// </param>
		protected internal virtual string declare_labels(production_part[] rhs, int rhs_len, string final_action)
		{
			System.String declaration = "";
			
			symbol_part part;
			// action_part act_part;
			int pos;
			
			/* walk down the parts and extract the labels */
			 for (pos = 0; pos < rhs_len; pos++)
			{
				if (!rhs[pos].is_action())
				{
					part = (symbol_part) rhs[pos];
					
					/* if it has a label, make declaration! */
					if (part.label() != null)
					{
						declaration = declaration + make_declaration(part.label(), part.the_symbol().stack_type(), rhs_len - pos - 1);
					}
				}
			}
			return declaration;
		}
		
		
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Helper routine to merge adjacent actions in a set of RHS parts 
		/// </summary>
		/// <param name="rhs_parts">array of RHS parts.
		/// </param>
		/// <param name="len">      amount of that array that is valid.
		/// </param>
		/// <returns>         remaining valid length.
		/// 
		/// </returns>
		protected internal virtual int merge_adjacent_actions(production_part[] rhs_parts, int len)
		{
			int from_loc, to_loc, merge_cnt;
			
			/* bail out early if we have no work to do */
			if (rhs_parts == null || len == 0)
				return 0;
			
			merge_cnt = 0;
			to_loc = - 1;
			 for (from_loc = 0; from_loc < len; from_loc++)
			{
				/* do we go in the current position or one further */
				if (to_loc < 0 || !rhs_parts[to_loc].is_action() || !rhs_parts[from_loc].is_action())
				{
					/* next one */
					to_loc++;
					
					/* clear the way for it */
					if (to_loc != from_loc)
						rhs_parts[to_loc] = null;
				}
				
				/* if this is not trivial? */
				if (to_loc != from_loc)
				{
					/* do we merge or copy? */
					if (rhs_parts[to_loc] != null && rhs_parts[to_loc].is_action() && rhs_parts[from_loc].is_action())
					{
						/* merge */
						rhs_parts[to_loc] = new action_part(((action_part) rhs_parts[to_loc]).code_string() + ((action_part) rhs_parts[from_loc]).code_string());
						merge_cnt++;
					}
					else
					{
						/* copy */
						rhs_parts[to_loc] = rhs_parts[from_loc];
					}
				}
			}
			
			/* return the used length */
			return len - merge_cnt;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Helper routine to strip a trailing action off rhs and return it
		/// </summary>
		/// <param name="rhs_parts">array of RHS parts.
		/// </param>
		/// <param name="len">      how many of those are valid.
		/// </param>
		/// <returns>         the removed action part.
		/// 
		/// </returns>
		protected internal virtual action_part strip_trailing_action(production_part[] rhs_parts, int len)
		{
			action_part result;
			
			/* bail out early if we have nothing to do */
			if (rhs_parts == null || len == 0)
				return null;
			
			/* see if we have a trailing action */
			if (rhs_parts[len - 1].is_action())
			{
				/* snip it out and return it */
				result = (action_part) rhs_parts[len - 1];
				rhs_parts[len - 1] = null;
				return result;
			}
			else
				return null;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Remove all embedded actions from a production by factoring them 
		/// out into individual action production using new non terminals.
		/// if the original production was:  <pre>
		/// A ::= B {action1} C {action2} D 
		/// </pre>
		/// then it will be factored into: <pre>
		/// A ::= B NT$1 C NT$2 D
		/// NT$1 ::= {action1}
		/// NT$2 ::= {action2}
		/// </pre>
		/// where NT$1 and NT$2 are new system created non terminals.
		/// </summary>
		
		/* the declarations added to the parent production are also passed along,
		as they should be perfectly valid in this code string, since it
		was originally a code string in the parent, not on its own.
		frank 6/20/96 */
		protected internal virtual void  remove_embedded_actions()
		{
			non_terminal new_nt;
			production new_prod;
			System.String declare_str;
			
			/* walk over the production and process each action */
			 for (int act_loc = 0; act_loc < rhs_length(); act_loc++)
				if (rhs(act_loc).is_action())
				{
					
					
					declare_str = declare_labels(_rhs, act_loc, "");
					/* create a new non terminal for the action production */
					new_nt = non_terminal.create_new();
					new_nt.is_embedded_action = true; /* 24-Mar-1998, CSA */
					
					/* create a new production with just the action */
					new_prod = new action_production(this, new_nt, null, 0, declare_str + ((action_part) rhs(act_loc)).code_string());
					
					/* replace the action with the generated non terminal */
					_rhs[act_loc] = new symbol_part(new_nt);
				}
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Check to see if the production (now) appears to be nullable.
		/// A production is nullable if its RHS could derive the empty string.
		/// This results when the RHS is empty or contains only non terminals
		/// which themselves are nullable.
		/// </summary>
		public virtual bool check_nullable()
		{
			production_part part;
			symbol sym;
			int pos;
			
			/* if we already know bail out early */
			if (nullable_known())
				return nullable();
			
			/* if we have a zero size RHS we are directly nullable */
			if (rhs_length() == 0)
			{
				/* stash and return the result */
				return set_nullable(true);
			}
			
			/* otherwise we need to test all of our parts */
			 for (pos = 0; pos < rhs_length(); pos++)
			{
				part = rhs(pos);
				
				/* only look at non-actions */
				if (!part.is_action())
				{
					sym = ((symbol_part) part).the_symbol();
					
					/* if its a terminal we are definitely not nullable */
					if (!sym.is_non_term())
						return set_nullable(false);
					else if (!((non_terminal) sym).nullable())
						return false;
				}
			}
			
			/* if we make it here all parts are nullable */
			return set_nullable(true);
		}
		
		/// <summary>set (and return) nullability 
		/// </summary>
		public virtual bool set_nullable(bool v)
		{
			_nullable_known = true;
			_nullable = v;
			return v;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Update (and return) the first set based on current NT firsts. 
		/// This assumes that nullability has already been computed for all non 
		/// terminals and productions. 
		/// </summary>
		public virtual terminal_set check_first_set()
		{
			int part;
			symbol sym;
			
			/* walk down the right hand side till we get past all nullables */
			 for (part = 0; part < rhs_length(); part++)
			{
				/* only look at non-actions */
				if (!rhs(part).is_action())
				{
					sym = ((symbol_part) rhs(part)).the_symbol();
					
					/* is it a non-terminal?*/
					if (sym.is_non_term())
					{
						/* add in current firsts from that NT */
						_first_set.add(((non_terminal) sym).first_set());
						
						/* if its not nullable, we are done */
						if (!((non_terminal) sym).nullable())
							break;
					}
					else
					{
						/* its a terminal -- add that to the set */
						_first_set.add((terminal) sym);
						
						/* we are done */
						break;
					}
				}
			}
			
			/* return our updated first set */
			return first_set();
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Equality comparison. 
		/// </summary>
		public virtual bool equals(production other)
		{
			if (other == null)
				return false;
			return other._index == _index;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Generic equality comparison. 
		/// </summary>
		public  override bool Equals(object other)
		{
			if (!(other is production))
				return false;
			else
				return equals((production) other);
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Produce a hash code. 
		/// </summary>
		public override int GetHashCode()
		{
			/* just use a simple function of the index */
			return _index * 13;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Convert to a string. 
		/// </summary>
		public override string ToString()
		{
			System.String result;
			
			/* catch any internal errors */
			try
			{
				result = "production [" + index() + "]: ";
				//UPGRADE_TODO: The equivalent in .NET for method 'java.Object.toString' may return a different value. 'ms-help://MS.VSCC/commoner/redir/redirect.htm?keyword="jlca1043"'
				result += ((lhs() != null)?lhs().ToString():"$$NULL-LHS$$");
				result += " :: = ";
				 for (int i = 0; i < rhs_length(); i++)
					result += rhs(i) + " ";
				result += ";";
				if (action() != null && action().code_string() != null)
					result += " {" + action().code_string() + "}";
				
				if (nullable_known())
					if (nullable())
						result += "[NULLABLE]";
					else
						result += "[NOT NULLABLE]";
			}
			catch (internal_error e)
			{
				/* crash on internal error since we can't throw it from here (because
				superclass does not throw anything. */
				e.crash();
				result = null;
			}
			
			return result;
		}
		
		/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
		
		/// <summary>Convert to a simpler string. 
		/// </summary>
		public virtual string to_simple_string()
		{
			System.String result;
			
			result = ((lhs() != null)?lhs().the_symbol().name_Renamed_Method():"NULL_LHS");
			result += " ::= ";
			 for (int i = 0; i < rhs_length(); i++)
				if (!rhs(i).is_action())
					result += ((symbol_part) rhs(i)).the_symbol().name_Renamed_Method() + " ";
			
			return result;
		}
		
		/*-----------------------------------------------------------*/
	}
}