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# Programming Language Concepts Programming Exam 3 solution

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CENG 242
Programming Language Concepts

Programming Exam 3

1 Problem Definition
As the 3rd programming exam, you will be guiding a rock sampling mission on the Planet Mars. There
will be Haskell functions to be implemented in 2 parts. Each function will be independently evaluated.
However, some functions are designed in an incremental manner. Therefore, using some of the requested
functions to implement some others (in/between parts) may really ease your job.
Figure 1: An Example Environment for The Mission

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## Description

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CENG 242
Programming Language Concepts

Programming Exam 3

1 Problem Definition
As the 3rd programming exam, you will be guiding a rock sampling mission on the Planet Mars. There
will be Haskell functions to be implemented in 2 parts. Each function will be independently evaluated.
However, some functions are designed in an incremental manner. Therefore, using some of the requested
functions to implement some others (in/between parts) may really ease your job.
Figure 1: An Example Environment for The Mission
Details for the mission and the environment are given in the following items (Re-reading them after seeing
the data types in Section 1.2 them is recommended).
• The task includes robots which are responsible to collect some samples from the cells containing
Rocks into the SpaceCraft in a grid-like 2D (M x N) environment as shown in Figure 1.
• No assumption should be done about the dimensions of the environment. M and N can be any
integer greater than 0.
• The environment can become severely challenging because it may have possible Pits where the
robots may get stuck and lose energy without being able to move.
• If a cell does not include any of these objects, it will be a Sand cell by default.
• The coordinate of (0,0) is the top-left corner cell of the environment. Therefore, in the sample
environment from Figure 1, (0,0), (4,0) and (1,2) are the cells including different amounts of Rocks.
SpaceCraft is located at (2,1) and there is a Pit at (3,2) in this sample environment.
1
• x-coordinate will be decreasing while going West and increasing while going East. y-coordinate will
be similarly affected by North/South actions. Be careful about handling these coordinates during
the operation on Grid as a nested list of Cell.
• As you may have already noticed the robots are not actual parts of the environment according to
the logic we use in our design. They can be at any location (even in the same location, without
any collision) in this environment, however, they do not change the representation of the cells.
• The robots have six possible moves: going toward one of the four main directions as North, East,
South, or West; PickUp one rock from a cell, and PutDown one rock from its storage to the spacecraft.
• The energy of a robot can be any integer in the range of [0,100] during the simulations.
• Each move of a robot will reduce its energy depending on the followings:
– Going toward one of the main directions will decrease the energy by 1.
– PutDown action will decrease the energy by 3.
– PickUp action will decrease the energy by 5.
• A robot must have the sufficient energy to complete an action.
• If a robot does not have the sufficient energy to take an action, its energy for the next step will be
0 without realization of the action effects over the environment and/or itself. For example, if the
robot gets a PickUp action with the energy level of 3, it will fail to pick a rock from the cell into its
storage. Namely, no change will occur in the environment and/or its storage, but its energy will be
set to 0.
• To be able to PickUp a rock, the robot must have less samples in its storage than its capacity.
Otherwise, the robot will lose energy without being able to fetch the rock.
• PickUp and PutDown actions will not be used in an invalid location. In other words, a PickUp
action will be given only for a Rock cell, and a PutDown action will be given in the cell containing
SpaceCraft. However, if a PickUp action has been taken in a Rock cell with no sample left (Rock
0), the robot will redundantly lose energy.
• Another redundant energy loss occurs, if the robots try to move out of the environment. For
example, if a robot takes a North action at the location (1,0), it will stay at the same location and
its energy will be decreased by 1.
• Details regarding the functions by themselves will be separately covered in their subsections.
1.2 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.
• We will use the following data types in the functions. They are already given in the template file.
You MUST them as is, no change on them is neither needed nor allowed.
2
data Cell = SpaceCraft Int | Sand | Rock Int | Pit deriving (Eq ,
type Grid = [[ Cell ]]
type Coordinate = (Int , Int )
data Move = North | East | South | West | PickUp | PutDown deriving
(Eq , Read , Show )
data Robot = Robot { name :: String ,
location :: Coordinate ,
capacity :: Int ,
energy :: Int ,
storage :: Int } deriving (Read , Show )
2 Functions
2.1 Part I – Stuff to Warm-up
2.1.1 isInGrid (7.5 points)
This is the simplest function in this exam. You will write a function called isInGrid to determine whether
a coordinate is within the borders of the given environment or not.
Here is the signature for this function:
isInGrid :: Grid – Coordinate – Bool
SAMPLE I/O:
* PE3 isInGrid [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] (0 ,2)
True
* PE3 isInGrid [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] (5 ,2)
False
* PE3 isInGrid [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] (0 , -2)
False
Note that the grid given in above samples is the same grid in Figure 1.
3
2.1.2 totalCount (10 points)
You will implement a function named totalCount having the signature below. This function will take a
grid and compute the total number of rocks in the environment (excluding the ones already gathered in
SpaceCraft). Obviously, if the environment does not have any rocks, it should return 0.
totalCount :: Grid – Int
SAMPLE I/O:
* PE3 totalCount [[ Sand , Sand , Sand , Sand , Pit ] , [ Sand , Sand , SpaceCraft
3 , Sand , Sand ] , [ Sand , Pit , Sand , Pit , Sand ]]
0
* PE3 totalCount [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]]
9
* PE3 totalCount [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 3 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]]
9
2.1.3 coordinatesOfPits (15 points)
The next function is coordinatesOfPits with the following signature:
coordinatesOfPits :: Grid – [ Coordinate ]
As the name implies, this function will take a grid and return the list of Coordinates for the cells containing a Pit. In the resulting list, the coordinates have to be ordered (in the increasing order primarily
with respect to x, then y), as shown in the samples below.
SAMPLE I/O:
* PE3 coordinatesOfPits [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand
, SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Sand , Sand ]]
[]
* PE3 coordinatesOfPits [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand
, SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]]
[(3 ,2) ]
* PE3 coordinatesOfPits [[ Rock 3 , Sand , Sand , Sand , Pit ] , [ Sand , Pit ,
SpaceCraft 3 , Sand , Sand ] , [ Sand , Pit , Sand , Pit , Sand ]]
[(1 ,1) ,(1 ,2) ,(3 ,2) ,(4 ,0) ]
4
2.1.4 tracePath (17.5 points)
You will implement a function called tracePath which will take a grid and a robot then produce the path
of a robot in simulation (according to the rules given in Section 1.1) as a list of Coordinates.
Here is the signature of this function:
tracePath :: Grid – Robot – [ Move ] – [ Coordinate ]
Obviously, PickUp and PutDown action has no effect on the location of the robot. Also note that the
coordinate will stay same if the energy of a robot is not sufficient and/or if it is in a cell containing a
Pit.
SAMPLE I/O:
* PE3 tracePath [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] Robot {
name =” Fetchy “, location =(2 ,1) , capacity =10 , energy =100 , storage =0} [
West , West , North , PickUp , South , East , East , PutDown ]
[(1 ,1) ,(0 ,1) ,(0 ,0) ,(0 ,0) ,(0 ,1) ,(1 ,1) ,(2 ,1) ,(2 ,1) ]
* PE3 tracePath [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] Robot {
name =” Fetchy “, location =(2 ,1) , capacity =10 , energy =3 , storage =0} [
West , West , North , PickUp , South , East , East , PutDown ]
[(1 ,1) ,(0 ,1) ,(0 ,0) ,(0 ,0) ,(0 ,0) ,(0 ,0) ,(0 ,0) ,(0 ,0) ]
* PE3 tracePath [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] Robot {
name =” Fetchy “, location =(2 ,1) , capacity =10 , energy =100 , storage =0} [
East , South , North , North , South , East , East , West ]
[(3 ,1) ,(3 ,2) ,(3 ,2) ,(3 ,2) ,(3 ,2) ,(3 ,2) ,(3 ,2) ,(3 ,2) ]
2.2 Part II – The Real Deal
2.2.1 energiseRobots (20 points)
You will implement a function named energiseRobots which simulates the wireless charging functionality of the SpaceCraft. When this functionality is triggered by calling energiseRobots with the given
list of Robots in the environment, each robot in the range of SpaceCraft will gain energy depending on
how far they are in the terms of Manhattan Distance. The function will return the list of updated Robot.
Additional energy for a robot will be calculated according to this formula:
gain = max(0, 100 − (|rx − sx| + |ry − xy|) × 20), (1)
where (rx, ry) and (sx, sy) are the coordinates of the robot and SpaceCraft respectively. While using this
formula, do not forget that the energy of a robot CANNOT exceed 100.
Here is the signature of this function:
energiseRobots :: Grid – [ Robot ] – [ Robot ]
5
SAMPLE I/O:
* PE3 energiseRobots [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] [ Robot {
name =” Fetchy “, location =(1 ,1) , capacity =10 , energy =0 , storage =0}]
[ Robot { name = ” Fetchy “, location = (1 ,1) , capacity = 10 , energy = 80 ,
storage = 0}]
* PE3 energiseRobots [[ SpaceCraft 3 , Sand , Sand , Sand , Rock 2] , [ Sand ,
Sand , Rock 3 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] [ Robot {
name =” Balboa “, location =(0 ,2) , capacity =10 , energy =3 , storage =1} ,
Robot { name =” Fetchy “, location =(4 ,2) , capacity =10 , energy =0 , storage
=0}]
[ Robot { name = ” Balboa “, location = (0 ,2) , capacity = 10 , energy = 63 ,
storage = 1} , Robot { name = ” Fetchy “, location = (4 ,2) , capacity = 10 ,
energy = 0 , storage = 0}]
2.2.2 applyMoves (30 points)
The last function is applyMoves which is very similar to tracePath function regarding its logic. However,
this time you will have to keep track of all action effects on both the environment and the robot itself. This
function returns the pair of the grid and the robot as a tuple representing their status after the simulation.
Here is the complete signature:
applyMoves :: Grid – Robot – [ Move ] – ( Grid , Robot )
SAMPLE I/O:
* PE3 applyMoves [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] Robot {
name =” Fetchy “, location =(2 ,1) , capacity =10 , energy =100 , storage =0} [
West , West , North , PickUp , South , East , East , PutDown ]
([[ Rock 2 , Sand , Sand , Sand , Rock 2] ,[ Sand , Sand , SpaceCraft 1 , Sand , Sand ] ,[
Sand , Rock 4 , Sand , Pit , Sand ]] , Robot { name = ” Fetchy “, location = (2 ,1) ,
capacity = 10 , energy = 86 , storage = 0})
* PE3 applyMoves [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] Robot {
name =” Fetchy “, location =(2 ,1) , capacity =10 , energy =3 , storage =0} [
West , West , North , PickUp , South , East , East , PutDown ]
([[ Rock 3 , Sand , Sand , Sand , Rock 2] ,[ Sand , Sand , SpaceCraft 0 , Sand , Sand ] ,[
Sand , Rock 4 , Sand , Pit , Sand ]] , Robot { name = ” Fetchy “, location = (0 ,0) ,
capacity = 10 , energy = 0 , storage = 0})
* PE3 applyMoves [[ Rock 3 , Sand , Sand , Sand , Rock 2] , [ Sand , Sand ,
SpaceCraft 0 , Sand , Sand ] , [ Sand , Rock 4 , Sand , Pit , Sand ]] Robot {
name =” Fetchy “, location =(2 ,1) , capacity =10 , energy =100 , storage =0} [
East , South , North , North , South , East , East , West ]
([[ Rock 3 , Sand , Sand , Sand , Rock 2] ,[ Sand , Sand , SpaceCraft 0 , Sand , Sand ] ,[
Sand , Rock 4 , Sand , Pit , Sand ]] , Robot { name = ” Fetchy “, location = (3 ,2) ,
capacity = 10 , energy = 92 , storage = 0})
6
3 Regulations
1. Implementation and Submission: The template file named “pe3.hs” is available in the Virtual
Programming Lab (VPL) activity called “PE3” 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