Homework 1 / Prerequisite Quiz

1. Prepare a plain text file aboutme.txt with the following information:

   Your name:
   Your student ID:
   Your major:
   Your preferred email address: 
   Check one: [ ] Undergraduate, [ ] Graduate, [ ] Open university 
   Repeating the class? [ ] Yes, [ ] No
   Semester, instructor, and grade of your CS151 prerequisite: 
   Time it took you to answer the question below:
   Did you ask anyone for help? [ ] Yes, [ ] No
   If adding: [ ] Section 3, [ ] Section 4, [ ] Either
   

2. Solve the problem below.
3. Make a private Git repo for all your work in this class. Put your work for this homework into a folder hw1, i.e. the files aboutme.txt, Op.java, Product.java, Read.java, and ExprTest2.java. Make sure these files do not have package declarations.
4. Add me as a contributor to your repo. My BitBucket and GitHub ids are cayhorstmann.
5. Send an email to Cay.Horstmann@sjsu.edu with subject line

   CS152 Repo

   and the URL to your repo in the body of your message. Also be sure that I can tell who you are from your email. Ever so often, I get an email where the sender is identified as something like GandalfTheUltimate or WildWeasel1989. That's not the professional presentation that we want to see from our graduates. If in doubt, use your SJSU email.
6. Run these commands:

   cd /tmp
   git clone your repo studentrepo
   cd studentrepo/hw1
   for f in Expr Const Function Sum Rand ExprTest ; do curl -O http://horstmann.com/sjsu/spring2018/cs152/hw1/$f.java ; done
   javac -cp .:path to JUnit4/\* -Xlint:unchecked *.java
   java -cp .:path to JUnit4/\* org.junit.runner.JUnitCore ExprTest
   

   Make sure that you pass all five tests.
7. There is no trust in this world. Add a screenshot to your repo that shows how you executed these commands, and the resulting output, in a file hw1/screenshot.png. (If you use the Lubuntu VM, you can run the scrot command to get a screen shot.)

Important: If you are currently enrolled in the class, you must turn in a complete or partial solution to this assignment by the deadline, or you may be dropped from the class. If you are trying to add the class, you will receive an add code after you have turned in the assignment and space becomes available.

You are given an interface Expr to evaluate expressions, a class Const that produces constant expressions, a class Rand that produces random integers, and an interface Function that defines a function with parameters and return value of type T.

• Complete the class Op that evaluates expressions of the form f(e₁, ..., e_n):

  public class Op<T> . . .
  {
     . . .
     @SafeVarargs public Op(Function<T> fun, Expr<T>... args)
     {
        . . .
     }
     . . .
  }
  

  An Op<T> is an Expr<T> (because it can be evaluated) and has Expr<T> (the arguments). Use the Composite design pattern. To evaluate the expression, invoke the function with a list of the arguments.
• The Op class is intended to be a superclass for operators such as Sum and

  public class Product . . .
  {
     @SafeVarargs public Product(Expr<Integer>... args)
     {
        . . .
     }
  }
  

  Implement Product without using streams. (Don't follow the implementation of Sum.)
• Complete the class Read that reads a single integer from standard input. You don't have to implement error handling.

  import java.util.Scanner;
  
  public class Read implements Expr<Integer>
  {
     private static Scanner in = new  Scanner(System.in);
     . . .
  }
  

• A JUnit 4 test ExprTest has been provided for your convenience.
• Provide a JUnit 4 test class ExprTest2 with at least three new test cases.