Assignment 0. Computer Science 52. Due Friday, September 7, 2018, at 5:00 pm

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Computer Science 52 Assignment 0 Due Friday, September 7, 2018, at 5:00 pm This assignment is simply to check out that you have access to and can use the SML system.

1 Computer Science 52 Assignment 0 Due Friday, September 7, 2018, at 5:00 pm This assignment is simply to check out that you have access to and can use the SML system. It is not factored into your course grade, but it is important that you complete it on time so that we can solve any problems that arise. Reading Material for the course is linked from the course web pages. Go to and click on the Resources tab in the blue bar at the top of the page. Find A Brief Introduction to SML, and read Part I. Now is a good time to become familiar with the available texts, which are also linked from the course Resources page. Take a look at the first few chapters of Ullman s book, Section 1.6 of Pucella s notes, the chapter Simple Applicative Programming by Gilmore, and Chapter 2 of Harper. Preparation Be sure you have an account. Most of you will have an account on the Computer Science Department systems from last semester or will have received with a password. See Corey LeBlanc in Edmunds 218 if you still need an account. If you plan on working on your own computer, configure your system SML setup right away. If you plan on working in the lab, go to the lab and login. One of the goals of this class is to make you more comfortable using the command-line in a terminal window. Follow the instructions in A Brief Introduction to SML to create a directory named cs052 for your work in this course. Slightly modified from com/224/

2 computer science 52, assignment 0 2 Template files Nearly every assignment will have a template file to get you started. One purpose of the file is to provide a standard format to ease our task of grading a large number of submissions. Another is to give you some starter code that you will use in the assignment. You will find the template file linked from the course Calendar page, right next to the assignment itself. For this assignment the file is named asgt00-template.sml Copy it to your working directory and name it asgt00.sml Then solve the problems on the assignment and place them in the designated places in the the file. Here is a sample from the template file for this assignment. ( Put your name and the date in the header comment here CS 52, Fall 2018 Assignment 0 ) ( $- ) ( Problem 1 $+00_01 ) ( numlist : int -> int list ) Place your solution to Problem 1 in this area ( Problem 2 $-00_01 $+00_02 ) ( sumlist : int -> int ) ( Problem 3 $-00_02 $+00_03 ) ( sumformula : int -> int ) Comments of the form (... ) are delimiters used by the grading scripts. Do not change or delete them. Place your entire solution to a given problem in the space between the delimiters, as shown above. You may include multiple functions as long as they appear between the problem delimeters. Check files Most assignments will have a check file that you can use to avoid some common errors. Using the check file makes it more likely that your work will successfully pass the grading scripts. For this assignment, copy the file

3 computer science 52, assignment 0 3 asgt00-check.sml from the course Calendar page to your working directory. When you are finished with the assignment, give the command sml asgt00-check.sml in the terminal window (not inside SML!). The check is successful if you see the words Sanity check successfully passed! If you do not see that message, go back and correct your code. Small errors often creep in during the last frenzied minutes when you are finishing an assignment. Remember to run the check file just before submitting your file. Keep in mind that the check file evaluates your code only for simple oversights, not for overall correctness. Submission Once you have completed the solution, made an attempt to understand the problems, and run the check file, submit your asgt00.sml file using the submission link on the course web page. The first time you use submission system you will need to Enroll in the course to be able to submit assignments. The assignment As you work on the assignment below, some of you will want to follow the instructions the instructions in A Brief Introduction to SML with extreme care, and others with a little more experience with Emacs and the command line will skim for the important details. However you do it, at the end of the exercise we want you to be able to create an SML file, correct errors in it, run it, and submit it. Take the time to read each line of your submission carefully and understand the significance of the system s responses. Feel free to ask questions if you find anything confusing or you encounter problems. Also, pay attention to the formatting and comments. Read the course s Style Guide in the document A Brief Introduction to SML, and make sure that your future submissions follow it. Because this is a warm-up assignment, the solutions are provided to you (in blue). All you have to do is to copy them into your file asgt00.sml. A complete solution appears at the end of this assignment. Although you are not expected to understand the solutions completely at this point in the course, take the time to look carefully at them and try to understand the general ideas. We will discuss the details in our first few classes. 1. Write a function numlist with the property that numlist n is a list of integers from n down to 1. numlist : int -> int list

4 computer science 52, assignment 0 4 fun numlist n = if 0 < n then n::(numlist (n-1)) else nil; 2. Write a function sumlist with the property that sumlist n is the sum of the integers from n down to 1. sumlist : int -> int fun sumlist n = if 0 < n then n + sumlist (n-1) else 0; 3. Write a function sumformula with the property that sumformula n gives the same result as sumformula n but uses the mathematical formula n + (n 1) = n(n+1) 2. sumformula : int -> int fun sumformula n = n (n+1) div 2; 4. Write a function samevalues that returns true when given two lists with the same lengths and the same values. Use list recursion even though it would be easier to write simply lista=listb. We ask you to write it in the more complicated way here to illustrate list recursion. samevalues : a list -> a list -> bool fun samevalues nil nil = true samevalues (x::xs) (y::ys) = x=y andalso samevalues xs ys samevalues = false; 5. Verify that the two ways of computing the sum of the first n integers give the same results, at least for the values from 47 down to 1. First create a list of integers from 47 down to 1, and then create two lists by applying the two functions to each element of the list. Then see if the two lists are equal, using samevalues. val baselist = numlist 47; val sivalues = map sumlist baselist; val sfvalues = map sumformula baselist; samevalues sivalues sfvalues;

5 computer science 52, assignment 0 5 Sample execution When you are finished and run your program, you Color coding: You type the material in green. The system responds with the should see something like the following in the terminal window. messages in purple. asgt00 28$ sml Standard ML of New Jersey v [built: Sun Dec 21 16:30: ] - use "asgt00.sml"; [opening asgt00.sml] val numlist = fn : int -> int list val sumlist = fn : int -> int val sumformula = fn : int -> int asgt00.sml:37.40 Warning: calling polyequal val samevalues = fn : a list -> a list -> bool val baselist = [47,46,45,44,43,42,41,40,39,38,37,36,...] val slvalues = [1128,1081,1035,990,946,903,861,820,780,741,703,666,...] val sfvalues = [1128,1081,1035,990,946,903,861,820,780,741,703,666,...] val it = true : bool val it = () : unit - Or, if you run the check file, you will see this. asgt00 29$ sml asgt00-check.sml Standard ML of New Jersey v [built: Sun Dec 21 16:30: ] [opening asgt00-check.sml] [autoloading] [library $SMLNJ-BASIS/basis.cm is stable] [autoloading done] [opening asgt00.sml] val numlist = fn : int -> int list val sumlist = fn : int -> int val sumformula = fn : int -> int asgt00.sml:37.40 Warning: calling polyequal val samevalues = fn : a list -> a list -> bool val baselist = [47,46,45,44,43,42,41,40,39,38,37,36,...] val slvalues = [1128,1081,1035,990,946,903,861,820,780,741,703,666,...] val sfvalues = [1128,1081,1035,990,946,903,861,820,780,741,703,666,...] val it = true : bool val it = () : unit Sanity check successfully passed! asgt00 30$

6 computer science 52, assignment 0 6 The sample program ( YourName TheDate CS 52, Fall 2018 Assignment 0 ) ( $- ) ( Problem 1 $+00_01 ) ( numlist : int -> int list ) fun numlist n = if 0 < n then n::(numlist (n-1)) else nil; ( Problem 2 $-00_01 $+00_02 ) ( sumlist : int -> int ) fun sumlist n = if 0 < n then n + sumlist (n-1) else 0; ( Problem 3 $-00_02 $+00_03 ) ( sumformula : int -> int ) fun sumformula n = n (n+1) div 2; ( Problem 4 $-00_03 $+00_04 ) ( samevalues : a list -> a list -> bool ) fun samevalues nil nil = true samevalues (x::xs) (y::ys) = x=y andalso samevalues xs ys samevalues = false; ( Problem 5 $-00_04 $+00_05 ) ( Verification that the two computations give equal values ) ( Create a list of integers from 47 down to 1, and create two lists by applying the two functions to each element of the list. Then see if the two lists are equal. ) val baselist = numlist 47; val slvalues = map sumlist baselist; val sfvalues = map sumformula baselist; samevalues slvalues sfvalues; ( $-00_05 )

A Second Look At ML. Chapter Seven Modern Programming Languages, 2nd ed. 1

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