CENG Programming Exam 1 Solution

    • Problem De nition

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 Speci cations

    • The signatures of the functions, their explanations and speci cations are given in the following section. Read them carefully.

    • Make sure that your implementations comply with the function signatures.

    • You may de ne 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:


g e t R o u n d e d    ::    Double    ->  Double

g e t R o u n d e d  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 le. You can use it directly, while outputting Double values. The whole purpose of using this function is the simpli cation of the output, which will be useful in both debugging and evaluation processes.








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    • 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:


co nv e rt TL    ::    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 > co nv er tT L 8180 "USD" 1000.0

    • PE1 > co nv er tT L 12500 "EUR" 1299.38

* PE1 >  co nv er tT L    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:


c o u n t O n W a t c h    ::  [ String ]  ->  String    ->  Int    ->  Int




    • 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.

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SAMPLE I/O:


* PE1 > c o u n t O n W a t c h [ "Ali" , " Huseyin " , " Ahmet " , " Derya " , "Ali" , " Fatma " , "Ali" , " Ahmet " ] " Ahmet " 5

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    • PE1 > c o u n t O n W a t c h [ "Ali" , " Huseyin " , " Ahmet " , " Derya " , "Ali" , " Fatma " , "Ali" , " Ahmet " ] "Ali" 5

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* PE1 > c o u n t O n W a t c h [ "Ali" , " Huseyin " , " Ahmet " , " Derya " , "Ali" , " Fatma " , "Ali" , " Ahmet " ] "Ali" 8

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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








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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 rst:


c o m p o u n d I n t e r e s t s    ::  [( Double ,  Int ) ]  ->  [ Double ]

This function takes a list of (Double, Int) pairs as the money and number of years for the invest-ment 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  1
(2)

12




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
>
c o m p o u n d I n t e r e s t s
[(15000 ,  1)]



[166
53.05]




*PE1
>
c o m p o u n d I n t e r e s t s
[(17557.5 ,  2) ,
(9800 ,
1) ]

[22073.68 ,10719.31]




*PE1 >
c o m p o u n d I n t e r e s t s
[(1575.25 ,  3) ,
(12500 ,
1)
,  (100000 ,  2)]
[2092.36 ,13877.54 ,125722.25]















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    • Regulations

        1. Implementation and Submission: The template le 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 le, complete the implementation and test it with the given sample I/O on your local machine. Then submit the same le 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 le.

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 les through OdtuClass. The last one you submitted will be graded.

    2. Cheating: We have zero tolerance policy for cheating. People involved in cheating (any kind of code sharing and codes taken from internet included) will be punished according to the university regulations.

    3. Evaluation: Your program will be evaluated automatically using \black-box" technique so make sure to obey the speci cations. No erroneous input will be used. Therefore, you don’t have to consider the invalid expressions.


Important Note: The given sample I/O’s are only to ease your debugging process and NOT o cial. Furthermore, it is not guaranteed that they cover all the cases of required functions. As a programmer, it is your responsibility to consider such extreme cases for the functions. Your implementations will be evaluated by the o cial testcases to determine your actual grade after the deadline.































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