Fully functional calculator built in React. Enforces logical rules around user input, such as:
- Expression must start with a number, ., or negative sign
- Expression cannot contain two operators in a row (with the exception of a minus sign)
- A number can only contain a single decimal point
- Pressing a number immediately following = should start a new calculation
- Pressing an operator immediately following = should start a new calculation that operates on the result of the previous evaluation
- Handles > 5 decimal places of precision with rounding, indicated by ~ symbol
