//controi todos os first(A) first(a) da gramatica g
FirstSets BuildFirstSets3(const Grammar& g)
{
FirstSets first;
//if X is a terminal: FIRST (X) = X
//X is epsilon: FIRST (X) = epsilon
for (int k = 0 ; k < g.GetNumOfGrammarSymbols(); k++)
{
if (g.GetSymbol(k)->IsTerminal())
{
std::set<const GrammarSymbol*> fs;
fs.insert(g.GetSymbol(k));
first.AddSet(g.GetSymbol(k), std::move(fs));
}
}
bool added = true;
while (added)
{
added = false;
for (int i = 0 ; i < g.GetNumOfProductions(); i++)
{
const Production& production = g.GetProduction(i);
const GrammarSymbol* X = production.GetLeftSymbol();
int epsilonCount = 0;
for (int k = 0 ; k < production.GetNumOfRightSymbols(); k++)
{
// Put FIRST (Y1) - {epsilon} into FIRST (X)
if (k == 0)
{
//Copia todos (-epsilon) de Y1first para Y1first(X)
auto Y1first = first.CreateGet(production.GetRightSymbol(k));
if (Y1first.find(g.epsilon()) != Y1first.end())
{
epsilonCount = 1;
}
for (auto it = Y1first.begin(); it != Y1first.end(); it++)
{
if (*it != g.epsilon())
{
const GrammarSymbol* ptemp = *it;
added = added || first.AddToSet(X, ptemp);
}
}
continue;
}
// O anterior tinha epsilon?
auto YKfirst = first.CreateGet(production.GetRightSymbol(k - 1));
if (YKfirst.find(g.epsilon()) != YKfirst.end())
{
epsilonCount++;
//Copia todos (-epsilon) para first(X)
auto Y1first = first.CreateGet(production.GetRightSymbol(k));
for (auto it = Y1first.begin(); it != Y1first.end(); it++)
{
if (*it != g.epsilon())
{
const GrammarSymbol* ptemp = *it;
added = added || first.AddToSet(X, ptemp);
}
}
}
else
{
//se o anterior nao tinha epsilon ja pode parar
break;
}
}
// se todos eram epsilon entao adicionar epsilon TODO -1
if (epsilonCount != 0 &&
epsilonCount == production.GetNumOfRightSymbols())
{
added = added || first.AddToSet(X, g.epsilon());
}
}
}
return first;
}
//controi todos os follow(A) da gramatica g
FollowSets BuildFolowSets3(Grammar& g, const FirstSets& first)
{
FollowSets follow;
//Follow(start-symbol):= {$};
follow.AddToSet(g.GetStartSymbol(), g.endmarker());
//for all nonterminals A != start-symbol do Follow(A):={};
for (int i = 0 ; i < g.GetNumOfGrammarSymbols(); i++)
{
const GrammarSymbol* pgs = g.GetSymbol(i);
if (!pgs->IsTerminal() && pgs != g.GetStartSymbol())
{
follow.CreateGet(pgs);
}
}
bool changed = true;
while (changed)
{
changed = false;
// Para cada producao A -> X1...Xn
for (int k = 0 ; k < g.GetNumOfProductions(); k++)
{
const Production& A = g.GetProduction(k);
Print(std::wcout, A);
std::wcout << std::endl;
for (int i = 0 ; i < A.GetNumOfRightSymbols(); i++)
{
//If there is a production A -> alfa B beta , then everything in FIRST(beta) except epsilon
//is in FOLLOW(B).
const GrammarSymbol* Xi = A.GetRightSymbol(i);
//Para cada nao terminal Xi da producao
if (!Xi->IsTerminal())
{
//add First(Xi+1..Xn) - {epsilon} to Follow(Xi)
std::set<const GrammarSymbol*> firstXi1_Xn;
bool epsilon_is_in_firstXi1_Xn = false;
//se Xi não é o ultimo
if (i < (A.GetNumOfRightSymbols() - 1))
{
firstXi1_Xn = GetFirstSet(first, g, A, i + 1);
for (auto it = firstXi1_Xn.begin(); it != firstXi1_Xn.end(); ++it)
{
if (*it != g.epsilon())
{
if (follow.AddToSet(Xi, *it))
{
changed = true;
}
}
else
{
epsilon_is_in_firstXi1_Xn = true;
}
}
}
// If there is a production A -> alfaB, or a production A -> alfa B beta , where
// FIRST(beta) contains epsilon, then everything in FOLLOW (A) is in FOLLOW (B) .
if (i == (A.GetNumOfRightSymbols() - 1) ||
epsilon_is_in_firstXi1_Xn)
{
//add Follow(A) to Follow(Xi)
auto FollowA = follow.Get(A.GetLeftSymbol());
for (auto it = FollowA.begin(); it != FollowA.end(); ++it)
{
if (follow.AddToSet(Xi, *it))
{
changed = true;
}
}
}
}//para este Xi
} //para cada Xi
} //para cada producao
} //enquando mudar...
return follow;
}
