
Project 2a  OCaml basics
Due 11:59pm Mon, September 28, 2015
Errata
 9/20, 8am  the specification for get_vals
was wrong for the case when some indexes were out of bounds
Introduction
The goal of this project is to get you familiar with programming in
OCaml. You will have to write a number of small functions, each of
whose specification is given below. In our reference solution, each
function's implementation is typically 36 lines of code; in a couple
of cases you will want to write a helper function which will add
another 36 lines.
This project is due in one week! We recommend you get started
right away, going from top to bottom, and the problems get
increasingly more challenging.
Getting Started
Download the following archive file p2a.zip
and extract its contents.
Along with files used to make direct submissions to the
submit server (submit.jar, .submit, submit.rb), you will
find the following project files:
 Your OCaml program  basics.ml
 Test utilities  testUtils.ml
 Public tests
 Expected outputs for public tests
 Ruby script to run public tests goTest.rb. Note that you will need to comment out
line 20 and uncomment out either line 21 or 22 in this file, depending
on which platform you are developing your code.
You may want to use functions from testUtils.ml for printing
debugging messages, but your actual submission in basics.ml
should not print any output nor should it depend on the testUtils.ml
file in any way.
To run an individual test, you can type commands like ocaml
testRecursion1.ml. The output from the test will be printed to
the console. You should compare it to the corresponding .out
to see if it is correct (this is what goTest.rb does).
Note that you must implement your functions with the exact
parameter and return type specified, or else the submit server
tests will fail.
For this project the only OCaml libraries you are allowed to
use are those defined in the
Pervasives
module loaded by default.
You are not allowed to use library functions found in any
other modules, particularly List and Array.
Part A: Simple functions
Write the following functions:
Name
 Type
 Return value
 Example

mult_of_five x
 int > bool
 true if x is a multiple of 5
false otherwise
 mult_of_five 5 = true
mult_of_five 1 = false

sum_upto_three ls
 int list > int
 the sum of the list's elements up to the first three
 sum_upto_three [1] = 1
sum_upto_three [1;2;3] = 6
sum_upto_three [1;2;3;4;5] = 6

caddr_int
 int list > int
 the second element of the list
1 if the list has 0 or 1 elements
 caddr_int [1;2;3] = 2
caddr_int [1] = 1

Part B: Simple Curried Functions
A curried function is one that takes multiple arguments "one at a
time". For example, the following function sub takes two arguments
and computes their difference:
let sub x y = x  y
The type of this function is int > int > int. Technically, this
says that sub is a function that takes an int and returns a
function that takes another int and finally returns the answer,
also an int. In other words, we could write
sub 2 1
and this will produce the answer 1. But we could also do something
like this:
let f = sub 2 in
f 1
and this will also produce 1. Notice how we call sub with only one
argument, so it returns a function f that takes the second
argument. In general, you can think of a function f of the type
t1 > t2 > t3 > ... > tn
as a function that takes n1 arguments of types t1, t2, t3, ...,
tn1 and produces a result of type tn. Such functions are written
with OCaml syntax
let f a1 a2 a3 ... = body
where a1 has type t1, a2 has type t2, etc.
Implement the following simple, curried functions:
Name
 Type
 Return value
 Example

mult_of_n x y
 int > int > bool
 whether x is a multiple of y
 mult_of_n 5 5 = true
mult_of_n 2 3 = false

triple_it x y z
 'a > 'b > 'c > 'a*'b*'c
 a tuple containing the three arguments, in order
 triple_it 5 5 5 = (5,5,5)
triple_it "hello" "b" "a" = ("hello","b","a")

maxpair (x,y) (m,n)
 'a*'b > 'a*'b > 'a*'b
 (x,y) if it is larger than (m,n), according to lexicographic
ordering
(m,n) otherwise (see note about comparison functions below)
 maxpair (1,2) (3,4) = (3,4)
maxpair (1,2) (1,3) = (1,3)

The OCaml comparison functions (=,<=,>=,<, and
>) are polymorphic, so you can give them any two
arguments of the same type.
Part C: Recursive Functions
The rest of the project asks that you implement a number of recursive
functions, many of which compute on lists.
Name
 Type
 Return value
 Example

prod l
 int list > int
 the product of all elements in l
1 if l is empty
 prod [5;6] = 30
prod [0;5;3] = 0

unzip l
 ('a*'b) list > ('a list)*('b list)
 a pair of lists consisting of the all first and second elements,
respectively, of the pairs in l
 unzip [(1,2);(3,4)] = ([1;3],[2;4])
unzip [(3,7);(4,5);(6,9)] = ([3;4;6],[7;5;9])

maxpairall l
 (int*int) list > int*int
 the largest pair in input list l, according to lexicographic ordering
(0,0) if l is empty
 maxpairall [(1,2);(3,4)] = (3,4)
maxpairall [(1,2);(1,3);(0,0)] = (1,3)

addTail l x
 'a list > 'a > 'a list
 a new list where x is appended to the end of l
 addTail [1;2] 3 = [1;2;3]

get_val x n
 int list > int > int
 element of list x at index n (indexes start at 0)
1 if n is outside the bounds of the list
 get_val [5;6;7;3] 1 = 6
get_val [5;6;7;3] 4 = 1

get_vals x y
 int list > int list > int list
 list of elements of list x at indexes in list y,
1 for any indexes in y are outside the bounds of x (as with get_vals)
elements must be returned in order listed in y
 get_vals [5;6;7;3] [2;0] = [7;5]
get_vals [5;6;7;3] [2;4] = [7;1]

list_swap_val b u v
 'a list > 'a > 'a > 'a list
 list b with values u,v swapped
change value of multiple occurrences of u and/or v, if found
change value for u even if v not found in list, and vice versa
 list_swap_val [5;6;7;3] 7 5 = [7;6;5;3]
list_swap_val [5;6;3] 7 5 = [7;6;3]

index x v
 'a list > 'a > int
 index of rightmost occurrence of value v in list x
(indexes start at 0)
1 if not found
 index [1;2;2] 1 = 0
index [1;2;2;3] 2 = 2
index [1;2;3] 5 = 1

distinct l
 'a list > 'a list
 a new list that contains the distinct elements of l, in the same
order they appear in l
 distinct [1;2;2] = [1;2]
distinct [2;1;2;2;3] = [2;1;3]

find_new x y
 'a list > 'a list > 'a list
 list of members of list x not found in list y
maintain relative order of elements in result
 find_new [4;3;7] [5;6;5;3] = [4;7]
find_new [5;6;5;3] [4;3;7] = [5;6;5]

is_sorted x
 'a list > bool
 true if elements in x are in sorted order, false otherwise
return true for []
 is_sorted [5;5;7;9] = true
is_sorted [9;7;5] = false

Submission
You can submit your project in two ways:

Submit your basics.ml file directly to the
submit server
by clicking on the submit link in the column "web submission".
Next, use the submit dialog to submit your basics.ml file directly.
Select your file using the "Browse" button,
then press the "Submit project!" button.
You do not need to put it in a Jar or Zip file.
Some students have mentioned problems
with using Internet Explorer, because
submissions being extracted in directories
(e.g., "C:\My Documents\330\basics.ml") where
the submit server could not find them. The
problems went away when switching to the
Mozilla Firefox browser.


Submit directly by executing a Java program on a computer
with Java and network access. Use the submit.jar file
from the archive p2a.zip.
To submit, go to the directory containing your project, then either
execute submit.rb or type the following command directly:
java jar submit.jar
You will be asked to enter your class account and password, then
all files in the directory (and its subdirectories) will be
put in a jar file and submitted to the submit server.
If your submission is successful you will see the message:
Successful submission # received for project 2a
Hints and Tips
Be sure you have read and understand the project grading policies in
the course syllabus. Do this well in advance of the project due date.
Academic Integrity
The Campus Senate has adopted a policy asking students to include the
following statement on each assignment in every course: "I pledge on
my honor that I have not given or received any unauthorized assistance
on this assignment." Consequently your program is requested to
contain this pledge in a comment near the top.
Please carefully read the academic honesty section of the
course syllabus. Any evidence of impermissible cooperation on
projects, use of disallowed materials or resources, or unauthorized
use of computer accounts, will be submitted to the Student
Honor Council, which could result in an XF for the course, or
suspension or expulsion from the University. Be sure you understand
what you are and what you are not permitted to do in regards to
academic integrity when it comes to project assignments. These
policies apply to all students, and the Student Honor Council does not
consider lack of knowledge of the policies to be a defense for
violating them. Full information is found in the course
syllabusplease review it at this time.
