**Due Date:** Monday, October 1, or Tuesday, October 2, 2007,
before the beginning of your lab section.

**Objective:** The main objective of this assignment is to practice
using conditional statements.

**Programming assignment:** Use JOptionPane to design a simple
function calculator for computing the values of elementary
functions. This function calculator should read simple expressions
like exp(-1.5), sin(0.0) or ln(1.0), and generate the result of the
corresponding arithmetic operation (or an error message if the user
wants to compute the logarithm of 0 or of a negative number). Let us
restrict ourselves to functions exp, ln, sin, and cos. For
simplicity, feel free to assume that the expressions do not have
blank spaces (but please inform the user about this restriction in
the input prompt).

**Hints:** You already know all the tricks that you need to build
such a function calculator:

- you know how to set up an input message box and how to read from such box -- we had that in Programming Assignment 3;
- you know how to check whether a given sequence-of-symbols string contains a given sequence such as exp -- it is in the book, and we had that in class; specifically, if the string contains the exp, the corresponding operation returns the location of this string, otherwise it returns -1;
- you know how to separate a part of the string after the given substring and before the final parenthesis;
- you know how to translate strings into real numbers -- we learned that when we learned how to read an number from the GUI;
- you know how to apply mathematical functions to real numbers;
- you know how to return the result -- and, if necessary, how to set up an error message box.

**Homework assignment:** on a separate sheet of paper, solve Ex. 10
from p. 218 and Ex. 12 from p. 219.

**Deliverables:** as instructed by your TA.