Method evaluate

src/common/StateDatabase.cpp:900–982

float StateDatabase::evaluate(Expression e) {
  std::stack<ExpressionToken> evaluationStack;
  ExpressionToken tok, lvalue, rvalue;
  bool unary;

  for (Expression::reverse_iterator i = e.rbegin(); i != e.rend(); i++) {
    unary = false;
    switch (i->getTokenType()) {
      case ExpressionToken::number: {
        evaluationStack.push(*i);
        break;
      }
      case ExpressionToken::variable: {
        // strip off '$'?
        tok.setNumber(eval(i->getVariable()));
        evaluationStack.push(tok);
        break;
      }
      case ExpressionToken::oper: {
        if ((i->getOperator() == ExpressionToken::lparen) ||
            (i->getOperator() == ExpressionToken::rparen)) {
          break;  // should not have any parens here, skip them
        }
        if (evaluationStack.size() == 0) {
          // syntax error
          return getNaN();
        }
        // rvalue and lvalue are switched, since we're reversed
        rvalue = evaluationStack.top(); evaluationStack.pop();
        if (evaluationStack.size() == 0) {
          unary = true; // syntax error or unary operator
        }
        if (!unary) {
          lvalue = evaluationStack.top(); evaluationStack.pop();
        }
        switch (i->getOperator()) {
          case ExpressionToken::add: {
            tok.setNumber(lvalue.getNumber() + rvalue.getNumber());
            evaluationStack.push(tok);
            break;
          }
          case ExpressionToken::subtract: {
            if (unary) {
              tok.setNumber(-rvalue.getNumber());
            }
            else {
              tok.setNumber(lvalue.getNumber() - rvalue.getNumber());
            }
            evaluationStack.push(tok);
            break;
          }
          case ExpressionToken::multiply: {
            tok.setNumber(lvalue.getNumber() * rvalue.getNumber());
            evaluationStack.push(tok);
            break;
          }
          case ExpressionToken::divide: {
            tok.setNumber(lvalue.getNumber() / rvalue.getNumber());