public bool IsPOS(string nonTerminal)
{
return(POSTypes.Contains(nonTerminal));
}
public void RemoveNonTerminalCounts(Rule rule)
{
var lhs = rule.Name.NonTerminal;
if (!nonTerminalCounts.ContainsKey(lhs))
{
throw new Exception(
string.Format("nonterminal {0} in rule {1} is missing from NonTerminalCounts dictionary", lhs, rule));
}
nonTerminalCounts[lhs].lhsCounts--;
var productionNonterminals = new List <string>();
if (!rule.IsEpsilonRule())
{
int i = 0;
foreach (var item in rule.Production)
{
var rhs = item.NonTerminal;
productionNonterminals.Add(rhs);
if (!nonTerminalCounts.ContainsKey(rhs))
{
throw new Exception(
string.Format("nonterminal {0} in rule {1} is missing from NonTerminalCounts dictionary",
lhs, rule));
}
nonTerminalCounts[rhs].rhsCounts--;
if (!RHSDictionary.ContainsKey(rhs))
{
throw new Exception(string.Format("nonterminal {0} in rule {1} is missing from RHSDictionary dictionary",
rhs, rule));
}
//remove from RHSDictionary.
RHSDictionary[rhs].Remove(new Tuple <int, int>(rule.Number, i));
i++;
}
}
var lhsCountsOfLHS = nonTerminalCounts[lhs]; //the counts of the Left-hand sided of the rule.
//if the removed rule has a LHS that no longer has any other LHS appearances, we can replace all its RHS appearances with another nonterminal,
//because we cannot invoke that non-terminal anymore.
if (lhsCountsOfLHS.lhsCounts == 0 && lhsCountsOfLHS.rhsCounts > 0 && !POSTypes.Contains(lhs) &&
lhs != StartSymbol)
{
//alternatively - do nothing. The resulting grammar will not use these rules.
}
var lhStoDelete = new List <string>();
if (!rule.IsEpsilonRule())
{
foreach (var item in productionNonterminals)
{
var rhsCountsofRhs = nonTerminalCounts[item]; //the counts of the right-hand sided of the rule terms
//if the removed rule has a specific RHS, X, that no longer has any other RHS appearances, we can delete the rules that has X as their LHS
//because they will not be triggered (orphaned rules)
if (rhsCountsofRhs.rhsCounts == 0 && rhsCountsofRhs.lhsCounts > 0 && !POSTypes.Contains(item) &&
item != StartSymbol)
{
var possiblePOS = item.Substring(0, item.Length - 1);
if (!POSTypes.Contains(possiblePOS))
{
lhStoDelete.Add(item);
}
}
}
}
foreach (var item in lhStoDelete)
{
var rules = Rules[item];
var removedRulesNumbers = rules.Select(x => x.Number);
foreach (var removedRuleNumber in removedRulesNumbers.ToArray())
{
DeleteRule(ruleNumberDictionary[removedRuleNumber]);
}
}
//after updating all counts of nonterminals in the rule, check if the type is still used.
//if not, remove it.
if (lhsCountsOfLHS.lhsCounts == 0 && lhsCountsOfLHS.rhsCounts == 0 && !POSTypes.Contains(lhs) &&
lhs != StartSymbol)
{
var possiblePOS = lhs.Substring(0, lhs.Length - 1);
if (!POSTypes.Contains(possiblePOS))
{
Console.WriteLine("removed type {0}", lhs);
NonTerminalsTypeDictionary.Remove(lhs);
nonTerminalCounts.Remove(lhs);
}
}
}