Method eval

src/MathExp.cpp:36–93

}

float MathExp::eval()
{
	unsigned int start = 0;
	for(unsigned int i = 0; i < mExpression.length(); i++)
	{
		if(isOperator(mExpression.at(i)))
		{
			//the string from start to i is an operand, and i is an operator
			if(start != i) //if we actually do have an operand
				mOperands.push(strToVal(mExpression.substr(start, i - start)));
			else
				std::cout << "skipping operand, start == i\n";

			//now we must decide what to do with the operator
			const char op = mExpression.at(i);

			if(op != *"(")
			{
				while(mOperators.size() && getPrecedence(mOperators.top()) >= getPrecedence(op))
				{
					doNextOperation();
				}
			}

			mOperators.push(op);

			start = i + 1;
		}else{
			if(isRParen(mExpression.at(i)))
			{
				while(mOperators.top() != *"(")
				{
					doNextOperation();
				}

				mOperators.pop();
			}
		}
	}

	mOperands.push(strToVal(mExpression.substr(start, mExpression.length() - start)));


	while(mOperators.size() > 0)
		doNextOperation();


	if(mOperands.size() != 1)
	{
		std::cout << "Error - mOperands.size() = " << mOperands.size() << " at the end of evaluation!\n";
		return 0;
	}

	float final = mOperands.top();
	mOperands.pop();

	return final;
}