/// <summary>
/// Main method for the process that removes the rules that have left recursion
/// </summary>
public void RemoveLeftRecursion()
{
int n = productionRules.Count;
bool foundRecursion = false;
for (var index = 0; index < n; index++)
{
try
{
if (productionRules[index].NonTerminal.Equals(productionRules[index].Rule[0]))
{
var sindex = index;
var nonterminal = productionRules[index].NonTerminal;
var newterminal = this.GenerateNonTerminal(nonterminal);
var newProdRule = new ProductionRule
{
NonTerminal = newterminal,
Rule = new List <string>()
};
productionRules.Add(newProdRule);
foundRecursion = true;
while (foundRecursion)
{
if (productionRules[sindex].NonTerminal.Equals(productionRules[sindex].Rule[0]))
{
var alpha = productionRules[sindex].Rule.GetRange(1, productionRules[sindex].Rule.Count - 1);
alpha.Add(newterminal);
productionRules[sindex].Rule = alpha;
productionRules[sindex].NonTerminal = newterminal;
}
else
{
productionRules[sindex].Rule.Add(newterminal);
}
sindex++;
if (!productionRules[sindex].NonTerminal.Equals(nonterminal))
{
foundRecursion = false;
index = sindex;
}
}
}
}
catch (System.ArgumentOutOfRangeException)
{
//exceptie daca intalneste cazul EPS (rule.count = 0)
}
}
productionRules = productionRules.OrderBy(o => o).ToList();
nonTerminals = nonTerminals.Distinct().ToList();
}
/// <summary>
/// Generates else if the nonterminal is already visited
/// </summary>
/// <param name="rule"></param>
/// <param name="code"></param>
/// <param name="nrBrace"></param>
/// <param name="nrIf"></param>
private void GenerateElse2(ProductionRule rule, ref string code, ref int nrBrace, ref int nrIf)
{
code += "}\n"; //closing the brace for last if
nrBrace--;
while (nrIf > 1)
{
code += "else { throw new Exception(\"ERROR\"); }\n";
code += "}\n";
nrBrace--;
nrIf--;
}
if (nrIf > 0)
{
try
{
if (_gramar.productionRules[_gramar.productionRules.IndexOf(rule) + 1].NonTerminal.Equals(rule.NonTerminal))
{
code += "else\n {\n";
nrIf--;
nrBrace++;
}
else
{
code += "else { throw new Exception(\"ERROR\"); }\n";
code += "}\n";
nrBrace--;
nrIf--;
code += "}";
nrBrace--; //
}
}
catch (System.ArgumentOutOfRangeException exc)
{
code += "else { throw new Exception(\"ERROR\"); }\n";
code += "}\n";
nrBrace--;
nrIf--;
code += "}";
nrBrace--; //
}
}
}
/// <summary>
/// The rules with the same begining are being corrected
/// </summary>
/// <param name="column"></param>
/// <param name="start"></param>
/// <param name="final"></param>
private void ModifyRulesSB_RSM(int column, int start, int final)
{
List <string> alpha = null;
column++;
if (column == 0)
{
alpha = productionRules[start].Rule.GetRange(0, column); //retin partea comuna;
}
else
{
alpha = productionRules[start].Rule.GetRange(0, column);
}
var newterminal = this.GenerateNonTerminal(productionRules[start].NonTerminal);
var oldterminal = productionRules[start].NonTerminal;
nonTerminals.Add(newterminal); //adaug noul neterminal in gramatica
//modific regulie astfel: daca A->alpha beta atunci o sa defina An->beta;
for (var ind = start; ind <= final; ind++)
{
var newprodRule = new ProductionRule
{
NonTerminal = newterminal,
Rule = productionRules[ind].Rule.GetRange(column, productionRules[ind].Rule.Count() - column),
};
//daca rule.count() == 0 atunci este EPS
productionRules[ind] = newprodRule;
}
//adaug regula de productie A->alphaA0;
var prodRule = new ProductionRule
{
NonTerminal = oldterminal,
Rule = alpha,
};
prodRule.Rule.Add(newterminal);
productionRules.Add(prodRule);
}
