The sqrt, exponent (^), and reciprocal (1/x) functions are not coded yet.
No keyboard handling yet, mouse clicks only.
The calculator should be able to handle (at least) the following cases:
- Any number of unclosed parentheses will automatically be closed and nested parens should calculate correctly.
- After entering an operator, entering another operator will replace the first one.
- Several invalid inputs will not update the display at all (digits after close parens with no operators, multiple decimal points, extra close parens, etc.)
- After evaluating a calculation, you can either use the result by entering an operator, or overwrite the result by entering a number.