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#include "nonterminal.ih"
// For an empty production, the N gets <empty>. For non-empty
// productions: add those element's first symbols, and stop if an
// element has no empty production. If, at the end, the final element
// has an empty production, add <empty> as well
void NonTerminal::setFirst(NonTerminal *nonTerminal)
{
FirstSet &firstSet = nonTerminal->d_first;
Production::Vector &prodVect = nonTerminal->d_production;
if (!prodVect.size()) // empty production
firstSet.addEpsilon(); // add epsilon to FirstSet
else
{
bool hasEpsilon = false; // include epsilon at the end?
for // visit all elements of a production
(
Production::Vector::const_iterator it = prodVect.begin();
it != prodVect.end();
++it
)
{
Production const &production = **it;
bool epsilon = true; // epsilon in this rule's elements
for
(
auto symPtrIt = production.begin();
symPtrIt != production.end();
++symPtrIt
)
{
firstSet += (*symPtrIt)->firstSet();
// add the element's firstSet
// element without <e>
if (!(*symPtrIt)->firstSet().hasEpsilon())
{
epsilon = false;
break; // and done, this productionrule
}
}
hasEpsilon |= epsilon; // once a production rule includes
// epsilon, hasEpsilon remains true
}
if (hasEpsilon)
firstSet.addEpsilon();
else
firstSet.rmEpsilon();
}
s_counter += firstSet.setSize();
}
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