Method infixToPrefix

src/common/StateDatabase.cpp:853–897

StateDatabase::Expression StateDatabase::infixToPrefix(const Expression& infix) {
  Expression postfix, prefix;
  std::stack<ExpressionToken> operators;

  for (Expression::const_iterator i = infix.begin(); i != infix.end(); i++) {
    if ((i->getTokenType() == ExpressionToken::variable) ||
        (i->getTokenType() == ExpressionToken::number)) {
      postfix.push_back(*i);
    }
    else if (i->getTokenType() == ExpressionToken::oper) {
      if (i->getOperator() == ExpressionToken::lparen) {
        operators.push(*i);
      }
      else if (i->getOperator() == ExpressionToken::rparen) {
        // unstack operators until a matching (is found
        while ((operators.size() > 0) &&
               (operators.top().getOperator() != ExpressionToken::lparen)) {
          postfix.push_back(operators.top()); operators.pop();
        }
        // discard (
        if (operators.size() > 0) { // handle extra-rparen case
          operators.pop();
        }
      }
      else {
        while ((operators.size() > 0) &&
               (operators.top().getPrecedence() < i->getPrecedence()) &&
               (operators.top().getOperator() != ExpressionToken::lparen)) {
          postfix.push_back(operators.top()); operators.pop();
        }
        operators.push(*i);
      }
    }
  }

  while (operators.size() > 0) {
    postfix.push_back(operators.top()); operators.pop();
  }

  for (Expression::reverse_iterator ri = postfix.rbegin(); ri != postfix.rend(); ri++) {
    prefix.push_back(*ri);
  }

  return prefix;
}


float StateDatabase::evaluate(Expression e) {