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# Programming Language Concepts Programming Exam 1 solution

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CENG 242
Programming Language Concepts

Programming Exam 1

1 Problem Definition
In this programming exam, you will help your friends who work in the IT department of a bank by
implementing some Haskell functions. Each function will correspond to an independent, small feature
which is useful for their customers or themselves in some certain calculations.
1.1 General Specifications
• The signatures of the functions, their explanations and specifications are given in the following
• Make sure that your implementations comply with the function signatures.
• You may define helper function(s) as you needed.

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## Description

CENG 242
Programming Language Concepts

Programming Exam 1

1 Problem Definition
In this programming exam, you will help your friends who work in the IT department of a bank by
implementing some Haskell functions. Each function will correspond to an independent, small feature
which is useful for their customers or themselves in some certain calculations.
1.1 General Specifications
• The signatures of the functions, their explanations and specifications are given in the following
• Make sure that your implementations comply with the function signatures.
• You may define helper function(s) as you needed.
• Importing any modules is not allowed for this exam. All you need is already available in the
standard Prelude module.
• Whenever you need to output a Double value (included in a list or by itself). You MUST use the
following function to round it to 2 decimal places:
getRounded :: Double – Double
getRounded x = read s :: Double
where s = printf “%.2f” x
This tricky implementation uses printf function from Text.Printf module. This import and
the implementation itself is already included in the template file. You can use it directly, while
outputting Double values. The whole purpose of using this function is the simplification of the
output, which will be useful in both debugging and evaluation processes.
1
2 Functions
2.1 convertTL (15 points)
You will implement a function named convertTL which takes a Double value and a String representing
the name of currency which the given money in Turkish Liras will be converted to. Here is the signature
of this function:
convertTL :: Double – String – Double
The abbreviations as representing Strings and the exchange rates 1
for the currencies are given in Table
1. No other currency will be tested.
Currency Abbreviation Exchange Rate
US Dollar “USD” 8.18
Euro “EUR” 9.62
Bitcoin “BTC” 473497.31
Table 1: Exchange Rates with TL for Currencies
The function must convert the money in TL to the given currency using the proper exchange rate and
return it as a Double.
SAMPLE I/O:
* PE1 convertTL 8180 “USD”
1000.0
* PE1 convertTL 12500 “EUR”
1299.38
* PE1 convertTL 1500000 “BTC”
3.17
2.2 countOnWatch (15 points)
As someone must monitor the servers of the bank at each night, some schedule is arranged for your
friends. Your task is to implement a function named countOnWatch which takes a list of Strings as
the schedule of the turns, a String representing the name of a certain employee and an Int representing
the some number of days. This function shall calculate the number of watches assigned to this employee
up to given days according to the arranged schedule. The function must return the calculated number as
an Int.
Here is the signature of this function:
countOnWatch :: [ String ] – String – Int – Int
1
I know that they look a little over-detailed, but let’s keep them in their realistic values for the time being. After
all we have the ability of copy/paste for such a burden.
2
SAMPLE I/O:
* PE1 countOnWatch [“Ali”, ” Huseyin “, ” Ahmet “, ” Derya “, “Ali”, ” Fatma “,
“Ali”, ” Ahmet “] ” Ahmet ” 5
1
* PE1 countOnWatch [“Ali”, ” Huseyin “, ” Ahmet “, ” Derya “, “Ali”, ” Fatma “,
“Ali”, ” Ahmet “] “Ali” 5
2
* PE1 countOnWatch [“Ali”, ” Huseyin “, ” Ahmet “, ” Derya “, “Ali”, ” Fatma “,
“Ali”, ” Ahmet “] “Ali” 8
3
2.3 encrypt (35 points)
You will implement a function named encrypt which takes an Int with 4 digits as the password of the
customer and returns an Int as the encrypted password by processing the digits in the original one.
Here is the signature of this function:
encrypt :: Int – Int
We will assume that the customers are not allowed to use a zero in any place for their password. Here
are the rules to encrypt the rest of the digits:
• If the digit is divisible by 3, you will subtract 1 from the digit.
• If the digit is divisible by 4, you will multiply the digit by 2.
• If the digit is divisible by 5, you will add 3 to the digit.
• For the rest of the cases, you will add 4 to the digit.
• If any of the above operation results in a double digit number, you will take the number in the
ones place (e.g. 6 for 16.).
SAMPLE I/O:
* PE1 encrypt 6475
5818
* PE1 encrypt 9812
8656
* PE1 encrypt 3597
2881
3
2.4 compoundInterests (35 points)
You will implement a function named compoundInterests which calculates the money the customers
would have after the compound interests are applied according to their initial money and how many years
they want to invest their money to the bank.
Rules for the calculation of the total money that each customer would get will be given below. Let’s look
at the signature of this function first:
compoundInterests :: [( Double , Int ) ] – [ Double ]
This function takes a list of (Double, Int) pairs as the money and number of years for the investment of each customer. The function returns a list of Double as the total money that each customer
would have for their investment. We will assume that there will be always at least one customer, when
this function is called.
As the bank has the policy to compound the money monthly, here is the formula for the calculation of
total money with compound interest:
T = P × (1 + R
12
)
12×N (1)
where T is the total money, P is the initial money, R is the annual interest rate and N is the number of
years. We will use Table 2 to calculate annual interest rate (R) for the given initial money (P).
Money ≥ 10000 Money < 10000
Years ≥ 2 11.5% 9.5%
Years < 2 10.5% 9.0%
Table 2: Annual Interest Rates
Let’s say that a customer initially has 15000 TL, and wants to keep their money for 1 year to get the
interest. Then we must use the annual interest rate as 10.5%. Hence, the calculation is done as below:
15000 × (1 + 0.105
12
)
12×1
(2)
By rounding the result to 2 decimal places, we get 16653.05 as the total money that customer would have
after 1 year.
SAMPLE I/O:
* PE1 compoundInterests [(15000 , 1) ]
[16653.05]
* PE1 compoundInterests [(17557.5 , 2) , (9800 , 1) ]
[22073.68 ,10719.31]
* PE1 compoundInterests [(1575.25 , 3) , (12500 , 1) , (100000 , 2) ]
[2092.36 ,13877.54 ,125722.25]
4
3 Regulations
1. Implementation and Submission: The template file named “pe1.hs” is available in the Virtual
Programming Lab (VPL) activity called “PE1” on OdtuClass. At this point, you have two options:
• You can download the template file, complete the implementation and test it with the given
sample I/O on your local machine. Then submit the same file through this activity.
• You can directly use the editor of VPL environment by using the auto-evaluation feature of
this activity interactively. Saving the code is equivalent to submit a file.
The second one is recommended. However, if you’re more comfortable with working on your local
machine, feel free to do it. Just make sure that your implementation can be compiled and tested
in the VPL environment after you submit it.
There is no limitation on online trials or submitted files through OdtuClass. The last one you