public Rule(Rule otherRule)
{
Name = new NonTerminalObject(otherRule.Name);
Production = otherRule.Production.Select(nonterminal => new NonTerminalObject(nonterminal)).ToArray();
HeadPosition = otherRule.HeadPosition;
ComplementPosition = otherRule.ComplementPosition;
Number = otherRule.Number;
Occurrences = otherRule.Occurrences;
}
public Rule(int occurrences, string name, string[] prod, int headPos = 0, int compPos = 1, int num = -1)
{
Name = new NonTerminalObject(name);
if (prod != null)
Production = prod.Select(nonterminal => new NonTerminalObject(nonterminal)).ToArray();
HeadPosition = headPos;
ComplementPosition = compPos;
Number = num;
Occurrences = occurrences;
}
public InverseKeyType(NonTerminalObject[] p, int h, bool isStart)
{
Production = p.Select(nonterminal => new NonTerminalObject(nonterminal)).ToArray();
HeadPosition = h;
IsStartSymbol = isStart;
}
private void Predict(Column col, List<Rule> ruleList, State state, NonTerminalObject currObject)
{
if (generator)
{
var rule = Grammar.GetRandomRuleForAGivenLHS(currObject.NonTerminal, true);
ruleList = new List<Rule> {rule};
}
foreach (var rule in ruleList)
{
//TODO: change later to skip -all- rules whose derivation leads to the empty string.
//I.e, A-> B.C , C -> D E. D -> epsilon, E -> epsilon. C itself is not an epsilon rule.
if (rule.IsEpsilonRule() && Grammar.nullableProductions.ContainsKey(currObject))
{
//states that are the result of a spontenous dot shift (due to nullable production)
//have already been added to the agendas in Column.Add()
continue;
}
//if current stack is empty but predicted stack is not, mismatch - do not predict this rule.
if (currObject.IsStackEmpty() && !rule.IsInitialOrDotStack()) continue;
//prepare new rule based on the stack information contained in the current state
//and based on the predicted rule.
var createdRule = new Rule(rule);
//if the rule is not a stack manipulating rule,
if (rule.IsInitialRule())
{
var complementPositionObject = createdRule.Production[createdRule.ComplementPosition];
//if current stack is not empty, but the complement position does not allow for stacks (POS),
//mismatch - do not predict this rule.
if (!currObject.IsStackEmpty() && Grammar.IsPOS(complementPositionObject.NonTerminal)) continue;
//the stack of the LHS of the created rule is the stack of the current object:
createdRule.Name = currObject;
//copy the stack to the complement position.
complementPositionObject.Stack = currObject.Stack;
}
else
{
if (createdRule.Name.Stack.Peek() != "." && currObject.Stack.Top != Grammar.Epsilon &&
currObject.Stack.Top != createdRule.Name.Stack.Peek())
continue;
//if tops of the stacks do not match, continue. e.g created rule PP[PP] -> epsilon, current object: PP[NP].
//create left hand side of new rule.
createdRule.Name.Stack = currObject.Stack;
createdRule.Name.NonTerminal = currObject.NonTerminal;
//create right hand side of new rule.
NonTerminalStack contentOfDot;
if (rule.Name.Stack.Peek() == ".")
contentOfDot = currObject.Stack; //e.g. A[..]
else
contentOfDot = currObject.Stack.GetPrefixListStackObjectOfGivenTop(rule.Name.Stack.Peek());
//e.g A[..X]
for (var i = 0; i < rule.Production.Length; i++)
{
var s = rule.Production[i].Stack;
if (s != null)
{
if (s.Peek() == ".")
createdRule.Production[i].Stack = contentOfDot; // e.g, A[..] pop rule.
else if (s.PrefixList == null)
createdRule.Production[i].Stack = s; //e.g. A[X] //secondary constituent.
else
createdRule.Production[i].Stack = new NonTerminalStack(s.Peek(), contentOfDot);
//e.g. A[..X] - push rule.
//calculate the new weight of the top of the stack from the weights of its sons.
//if (createdRule.Production[i].Stack != null)
// createdRule.Production[i].Stack.Weight = createdRule.Production[i].Stack.PrefixList != null ? createdRule.Production[i].Stack.PrefixList.Sum(x => x.Weight) : 1;
}
}
}
var newState = new State(createdRule, 0, col, null) {LogProbability = ruleLogProbabilities[rule.Number]};
if (newState.LogProbability < 0)
throw new Exception("wrong probability");
var added = col.AddState(newState, ParsingOperation.Predict);
if (Debug)
Console.WriteLine("{0} & {1} & {2} & Predicted from State {3}, added: {4}\\\\", newState.StateNumber,
newState,
col.Index, state.StateNumber, added);
}
}
private bool IsCompletedTermConsistentWithNextTerm(NonTerminalObject completedTerm, NonTerminalObject nextTerm,
out NonTerminalStack intersection)
{
intersection = null;
if (nextTerm == null) return false;
//the above case happens where the rule to be continued is already completed at the start column (next term = null).
//this can only happen in a single case: that rule was an epsilon rule.
if (completedTerm.NonTerminal != nextTerm.NonTerminal)
return false;
if (nextTerm.Stack == null && completedTerm.Stack == null) return true;
NonTerminalStack arg1 = null;
//deep copy the stacks in order not to alter the graphs of past stacks.
if (nextTerm.Stack != null)
arg1 = new NonTerminalStack(nextTerm.Stack, true);
NonTerminalStack arg2 = null;
if (completedTerm.Stack != null)
arg2 = new NonTerminalStack(completedTerm.Stack, true);
intersection = NonTerminalStack.Intersect(arg1, arg2, new HashSet<NonTerminalStack>(),
new HashSet<NonTerminalStack>(),
new Dictionary<NonTerminalStack, HashSet<NonTerminalStack>>());
return intersection != null;
}
