Description
This assignment consists of three F# exercises. The code for all exercises are to be included in a
single file named hw4.fsx.
1. replace list origVal newVal: The function takes a list of integers (list), an integer to
be replaced (origVal), and a replacement integer (newVal). The function returns a list such that
each occurrence of origVal in list is replaced with newVal. All other elements remain
unchanged.
Examples:
> replace [1; 2; 3; 2; 2; 4; 2; 5] 2 6;;
val it : int list = [1; 6; 3; 6; 6; 4; 6; 5]
2. mergeList listA listB: Both parameters are lists of integers. The function returns a list
that merges the lists in alternating fashion. The first item in the first item from listA, the second
item is the first item from listB, the third item is the second item form listA, and so on.
Continue in this fashion until one list runs out; then append the remaining items from the longer
list.
Examples:
> let m1 = [1; 2; 3; 4; 5; 6];;
> let m2 = [7; 8; 9; 10];;
> mergeList m1 m2;;
val it : int list = [1; 7; 2; 8; 3; 9; 4; 10; 5; 6]
3. Write the following functions for a dictionary. The dictionary is implemented using a list of
tuples. Each tuple represent a key-value pair has two items: the first is a string and represents the
key, the second is an integer and represents the value. The dictionary is unordered and each key
must be unique.
a. search dict key: Returns an option type with the corresponding value is if the key is in the
dictionary and None if the key is not in the dictionary.
b. insert dict key value: If the key is not already in the dictionary, a new dictionary is
returned with the key-value pair inserted into the dictionary. If the key is already in the dictionary,
return the dictionary with no modifications.
2
c. remove dict key: If the key is in the dictionary, a new dictionary is returned with the
corresponding key-value pair removed. If the key is not in the dictionary, return the dictionary
with no modifications.
d. count dict func: The parameter func is a Boolean function that takes a single integer
parameter and returns true or false. The function calls func with each value (of the key-value
pair) and returns the number of nodes that evaluate to true.
e. twoDigitCount dict: Returns the number of entries that have a two-digit positive integer
(10 to 99) value. REQUIREMENT: This function must be a single call to count using a lambda
function.
Examples:
> let fruits = [(“apple”, 5); (“pear”, 73); (“lime”, 42); (“orange”, 8);
(“kiwi”, 17)];;
> search fruits “pear”;;
val it : int option = Some 73
> search fruits “banana”;;
val it : int option = None
> insert fruits “pear” 16;;
val it : (string * int) list =
[(“apple”, 5); (“pear”, 73); (“lime”, 42); (“orange”, 8); (“kiwi”, 17)]
> insert fruits “banana” 44;;
val it : (string * int) list =
[(“banana”, 44); (“apple”, 5); (“pear”, 73); (“lime”, 42); (“orange”, 8);
(“kiwi”, 17)]
> remove fruits “pear”;;
val it : (string * int) list =
[(“apple”, 5); (“lime”, 42); (“orange”, 8); (“kiwi”, 17)]
> remove fruits “banana”;;
val it : (string * int) list =
[(“apple”, 5); (“pear”, 73); (“lime”, 42); (“orange”, 8); (“kiwi”, 17)]
> let countAll x = true;;
val countAll : x:’a -> bool
> let countEven x = x % 2 = 0;;
val countEven : x:int -> bool
> count fruits countAll;;
val it : int = 5
> count fruits countEven;;
val it : int = 2
> twoDigitCount fruits;;
val it : int = 3
3
Implementation Notes:
• You may define and use additional functions if your feel it is appropriate.
• Functions must match the order of parameters given.
• As long as the functions accept the specified types, it is permissible for the functions to be
generic and accept other types. In other words, you should not have to specify the types of any
parameters unless it is necessary for correct functionality.
• Without prior approval from me, you may only use the subset of F# described in class.
o In particular, you may NOT use F# system functions or methods (especially those in
the map module).
• You are only required to write the provided functions. There is no additional global
functionality. Your program should produce no output and accept no input.
• To test your functions, either:
o Test the functions using an interactive interpreter OR
o Add your own tests to the script (but be sure to remove them before submission!)
Submitting your Assignment
To submit your assignment, you will need to transfer your file to cs1. On cs1, run the following
script in the directory with your program:
/home/fac/bdiazacosta/submit/cpsc3400/hw4_submit
This will copy the files hw4.fsx to a directory that can be accessed by the instructor. Please be
sure to keep the same file name or the submission program will not work. Only the last assignment
submitted before the due date and time will be graded. Late submissions are not accepted and
result in a zero.
4
Grading
Grading is based on the following rubric and is primarily based on functionality based on how
many tests pass or fail.
Feature Max
Points
replace
• Provided example: 2 points
• 6 additional tests: 1 point each
8
mergeList
• Provided example: 2 points
• 6 additional tests: 1 point each
8
search
• 2 provided examples: 2 points each
• 3 additional tests: 1 point each
7
insert
• 2 provided examples: 2 points each
• 3 additional tests: 1 point each
7
remove
• 2 provided examples: 2 points each
• 3 additional tests: 1 point each
7
count
• 2 provided examples: 2 points each
• 3 additional tests: 1 point each
7
twoDigitCount
• Provided examples: 2 points
• One additional test: 1 point
• Properly implemented using a single call to count with a lambda function: 3 points
6
TOTAL 50
The following additional deductions are possible:
• Programs may lose up to 10 points if they exhibit poor readability or style.
• Using F# constructs or system functions outside the subset in class will result in a deduction.
Severe deductions are possible if the use significantly simplifies one of the functions and/or
results in a style that is not pure functional programming. I also reserve the right to require a
resubmission.
• Programs that contain syntax errors will receive a zero.
