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This assignment is worth 10% of your Tnal grade.
Indicative marks and feedback for Part A will be returned in week 6.
Deadlines:
Part A: Sunday March 22, 2020, at 11:00pm Canberra time sharp Part B: Sunday April 12, 2020, at 11:00pm Canberra time sharp
COMP1100
COMP1130
Task 1: Helper Functions
20 marks
10 Marks
Task 2: Rendering Shapes
35 marks
30 Marks
Task 3: Handling Events
30 marks
25 Marks
1130 Extensions
30 Marks
Technical Report
15 marks
25 Marks
The purpose of Part A is to give you an opportunity to collect feedback on your code and your progress in the course, and for us to give you an indicative mark for your work so far. This will be returned to you before the census date. Part A will be re-marked alongside your Part B submission, giving you a Tnal mark for the assignment.
You should execute these cabal commands in the top-level directory of your project: ~/comp1100/assignments/assignment1 (i.e., the directory you are in when you launch the VSCodium Terminal for your project).
Action
Effect
Esc (key)
Clear the canvas
M (key)
Display a mystery image
C (key)
Cycle colour (of shape to draw)
T (key)
Cycle tool (type of shape to draw)
Backspace/Delete (key)
Remove the last added shape
D (key)
Print the current Model to the terminal (useful for testing)
Click-drag-release (mouse)
When not drawing polygons, draw a shape between the click- point and release-point
Click (mouse)
When drawing polygons, add a point to the polygon
Spacebar (key)
Finish drawing a polygon, adding it to the canvas.
Tool
Label
LineTool
“Line… click-drag-release”
PolygonTool
“Polygon… click 3 or more times then spacebar”
RectangleTool
“Rectangle… click-drag-release”
CircleTool
“Circle… click-drag-release”
EllipseTool
“Ellipse… click-drag-release”
SectorTool
“Sector… click-drag-release”
Argument
Result
Black
Red
Red
Orange
Orange
Yellow
Yellow
Green
Green
Blue
Blue
Violet
Violet
Black
Note that the Tool and the ColourName do not reset to the default values after a shape has been drawn. However, the Maybe Point inside the tool revert to Nothing.
Key
Effect
C
Cycle colour (of shape to draw)
T
Cycle tool (type of shape to draw)
Backspace/Delete
Remove the last added shape
Spacebar
Finish drawing a polygon, adding it to the canvas.
Do not try to claim that “everything is similar to everything else”. That would collapse this problem to “erase the entire canvas”, which is too easy.
Once again: These are not required word counts. They are the maximum number of words that your marker will read. If you can do it in fewer words without compromising the presentation, please do so.
This is a list of suggestions, not requirements. You should only discuss items from this list if you have something interesting to write.
Before the assignment is due, course staff will not give individual tips on writing functions for the assignment or how your code can be improved. We will help you get unstuck by asking questions and pointing you to relevant lecture and lab material. You will receive feedback on you work when marks are released.
COMP1100/1130 [2020 S1]:
PROGRAMMING AS PROBLEM SOLVING Research School of Computer Science
» Assignments » Assignment 1: Shapes
In this assignment, you will build a Haskell program that uses the CodeWorld API to draw colourful shapes on the screen, including lines, polygons, rectangles, circles, ellipses, and sectors.
Required Knowledge
If you have Tnished the week 3 lab, you should be able to complete Part A.
If you have Tnished the week 4 lab, you should be able to complete the majority of the assignment. Some parts require recursion over lists, which is covered in the week 5 lab.
Overview of Tasks
You will be required to complete different tasks depending on your enrolled course:
Part A of the assignment requires you to complete Task 1. PartB of the assignment requires you to complete all assigned tasks. As you complete each task (or even each function within a task), you should commit and push your work with a sensible commit message.
Getting Started
1. Fork the assignment repository and create a project for it in VSCodium, following the same steps as in Lab 2. The assignment repository is at https://gitlab.cecs.anu.edu.au/comp1100/2020s1studentTles/assignment1.
2. Add our version of the repository as a remote called upstream. This allows us (the tutors) to provide additional Txes if they are required. You do this by doing the following:
Go to the command palette in VSCodium by pressing Ctrl + Shift + p Type git remote
Click Git: Add Remote
Enter upstream into the box for the remote name
Put the following URL as the remote url: https://gitlab.cecs.anu.edu.au/comp1100/2020s1studentfiles/assignment1.git.
Overview of the Repository
Most of your code will be written to Haskell Tles in the src/ directory. We are using the model-view-controller pattern to structure this assignment. Each Tle is called a module, and we use modules to group related code together and separate unrelated code.
Model.hs
The model is a data type that describes the state of the running program. The program will move to new states (new values of type Model) in response to user actions, as deTned by the controller.
View.hs
The view turns the model into something that can be shown on the screen; in this project, that is the CodeWorld Picture type.
Controller.hs
The controller considers user input (and other events), along with the current model, and uses that to decide what the new model should be.
Other Files
tests/ShapesTest.hs contains some unit tests – simple checks that verify small parts of your program are working correctly. You are not required to write tests for this assignment, but you might Tnd it useful to do so.
tests/Testing.hs is a small testing library used by tests/ShapesTest.hs. You are not required to understand it for this assignment.
app/Main.hs ties your functions together into the Tnal program that runs. You are not required to understand it.
comp1100-assignment1.cabal tells the cabal build tool how to build your assignment. You are not required to understand this Tle, and we will discuss how to use cabal below.
Setup.hs tells cabal that this is a normal package with no unusual build steps. Some complex packages (that we won’t see in this course) need to put more complex code here. You are not required to understand it.
Overview of Cabal
cabal is the build tool for Haskell programs and libraries. It provides several useful commands:
cabal v2-build: Compile your assignment.
cabal v2-run shapes: Build your assignment (if necessary), and run the shapes
program.
cabal v2-repl comp1100-assignment1: Run the GHCi interpreter over your project. This gives you the same ghci environment you use in labs, but with the assignment code loaded. (Aside: REPL is the name for interactive sessions like GHCi – it stands for read-eval-print loop. Many modern languages have REPLs.)
cabal v2-test: Build and run the tests. Tests will abort on the Trst failure, or the Trst call to a function that is still undefined.
Overview of the Program
You use a web browser to interact with the shapes program that you launched with cabal v2-run shapes. Once you have completed the assignment, it will respond to the following actions:
Task 1: Helper Functions (COMP1100: 20 marks; COMP1130: 10 marks)
The easiest way to solve a large problem is often to break it apart into smaller, easier problems. Programming is the same. In this task you will write some helper functions that will make future tasks easier. You can test your implementations by running cabal v2-test.
The functions you need to write for this task are:
toolToLabel in src/View.hs. This function should return instructions for the user
on how to use each Tool, according to the following table:
Note: At the time this assignment is released, the course will have only briefy covered lists. You do not need to manipulate lists to write toolToLabel; you can use a blank pattern (_) to ignore them.
nextColour in src/Controller.hs. This function should return the next colour in our set of ColourNames:
nextTool in src/Controller.hs. This function implements tool-switching, but should not change Tool if the user is halfway through an operation:
If the tool is not holding a point (that is, a non-PolygonTool tool holding Nothing or a PolygonTool holding the empty list []), select the next tool in the following sequence: Line -> Polygon -> Rectangle -> Circle -> Ellipse – > Sector -> Line -> ….
If there is a Point stored in the given tool (because it’s holding a Just value or the list in PolygonTool is non-empty), return the argument unchanged.
If this is unclear, study the nextToolTests in test/ShapesTest.hs.
Note: At the time this assignment is released, the course will have only briefy covered lists. You can write the PolygonTool case for nextTool without using list recursion. Use [] to match an empty list. In a subsequent case, give the entire list a name like points to match any nonempty list. Alternatively, you might use the Prelude function
Part A ends here. *****
Submitting Part A
Your submission for Part A should include implementations of toolToLabel, nextColour and nextTool that compile without warnings and pass the tests run by cabal v2-test. You are welcome to continue working on Part B of your assignment and committing and pushing changes, so long as the code continues to compile and the tests continue to pass.
Part B begins… *****
Task 2: Rendering Shapes (COMP1100: 35 marks; COMP1130: 30 marks)
In src/View.hs, modelToPicture converts your Model type into a CodeWorld Picture, so that it can be displayed on the screen. It currently does not work, because colourShapesToPicture is undefined. In this task you will Tll in that missing piece, building up a function to convert the [ColourShape] from your Model into a Picture. You can test these functions individually by using cabal v2-repl comp1100-assignment1, using drawingOf to show small pictures on the screen. You can also test everything as a whole by launching the program with cabal v2-run shapes and pressing the M key to show the mystery image. The functions you need to write for this task are all in src/View.hs:
colourNameToColour: This function turns your ColourName type from the model into a CodeWorld Colour. You should check the CodeWorld documentation for information on colours.
shapeToPicture: This function turns your Shape type into a CodeWorld Picture. You will need to consider the constructors for Shape individually, and work out the best way to turn each one into a Picture. Here are some hints to help you along:
CodeWorld has no function to draw a single line segment. It does have a function to draw a line made of multiple segments – polyline.
Polygons, rectangles, circles and ellipses should be drawn as solid (Tlled) Pictures.
Sectors should be drawn starting from 0 radian and ending with the angle between the line connecting the two Points and the horizontal line from the center towards positive inTnity. The Trst Point should be the center of the circle that the sector is in. For example, Sector (3,1) (-1,-2) should draw a sector which starts at 0 radian, ends at (1.57+1.57+0.64) radians, and centered at (3,1) as in the picture below.
90 degrees = 1.57 radians
Inverse tangent of 0.75 is approximately 0.64.
You can use atan function to compute inverse tangent.
Most of CodeWorld’s functions draw individual shapes centred on the origin – (0, 0). You will need to Tgure out how to slide (translate) the generated Picture so it winds up where it’s supposed to go. Drawing diagrams will help. The abs function will also help – it computes the absolute value of its argument (i.e., abs x == x if x > 0, and abs x == negate x otherwise).
Ellipses are speciTed as two opposite coordinates for a bounding box that wraps the ellipse. CodeWorld has no primitive that draws an ellipse, but an ellipse is a stretched circle. Does CodeWorld have a function to stretch (scale) a Picture?
You do not have to completely implement this function before moving onto others. If you have written code to render Rectangles but nothing else, you can create a drawing out of Rectangles only, and check that your other functions work, before returning to Tnish shapeToPicture.
colourShapeToPicture: This function should render the Shape and colour it using the Colour that corresponds to the given ColourName.
colourShapesToPicture: This function should turn every ColourShape in a list into a single Picture. You will need to recurse over the input list. If you have not yet completed Lab 5, you may want to work on other parts of the assignment and come back to this.
Task 3: Handling Events (COMP1100: 30 marks; COMP1130: 25 marks)
It is now time to tackle handleEvent in src/Controller.hs. CodeWorld calls this function whenever something interesting happens (like a key press, a pointer press, or a pointer release). This function is called with two arguments:
The Event that just happened, and
The current Model at the time the Event happened.
handleEvent then returns a new Model for the program to use moving forward. (Aside: Elm is a functional programming language that uses a similar pattern to build
front-end web applications that are compiled to JavaScript.)
Let’s trace a simple interaction. If the user wants to draw a red line by clicking on the screen at coordinates (1, 1) and releasing the mouse at coordinates (2, 2). starting at a blank canvas, the state would transition as follows, starting with the initial model:
1. Model [] (LineTool Nothing) Black
2. The user presses “C” to change the colour from red to black:
Model [] (LineTool Nothing) Red
3. The user presses the mouse button at (1, 1) changing the state to Model [] (LineTool (Just (1.0,1.0))) Red
4. The user releases the mouse button at (2, 2) changing the state to Model [(Red,Line (1.0,1.0) (2.0,2.0))] (LineTool Nothing) Red
Task 3.1: Handling Mouse Input
CodeWorld provides a few different event constructors for mouse input, but the ones we’re interested in are PointerPress for when the user clicks, and PointerRelease for when the user releases the mouse button.
When a PointerPress event arrives, you will need to store it in the current Tool. For everything except PolygonTool, you will store it in the Maybe Point argument. For PolygonTool, you will add it to the list of vertices.
When a PointerRelease event arrives, we can ignore it for PolygonTool because we’ll Tnish polygons using the spacebar in Task 3.2. For everything else, a PointerRelease means the end of a click-drag-release action, so you should construct the appropriate shape and add it to the [Shape] in the Model. You should also remove the starting point from the current Tool, so that future shapes draw properly too.
Task 3.2: Handling Key Presses
To handle keyboard input, CodeWorld provides a KeyPress event. This case is already present in the assignment skeleton, because we have implemented some keyboard functionality already. In the “Overview of the Program” section, we listed the full set of keyboard commands that your program will respond to. You need to implement the missing functionality for these keys:
If you have made it this far, you should not need to write a lot of code to implement these. A few hints:
Think back to Task 1.
Backspace/Delete with no shapes drawn should not crash the program.
Task 4: Extensions (COMP1130 Only: 30 marks)
COMP1100 students are welcome to attempt extensions, but will not attract marks for completing them.
COMP1130 students will need to complete two of the Tve extensions in the pool below. If you attempt more than two extensions, you must indicate in your report which ones should be marked. Otherwise, we will mark the Trst extensions that you have attempted, according to the order they appear in this document.
If you change the behaviour of tool or colour switching, you may want to adjust the tests in tests/ShapesTest.hs so they continue to pass.
Note: Extension functionality must be executed through the CodeWorld API just like the rest of the assignment. Interactions should be received through the handleEvent function, which you will need to modify. If you need to add Telds to the Model constructor, please do so after the existing ones: data Model = Model [ColourShape] Tool ColourName YourField1 YourField2 ….
Task 4.1
Allow the user to delete multiple shapes using the mouse. The user should enter some kind of “mouse delete mode”, and then delete multiple shapes at once by pressing the mouse button and dragging a rectangle around them. When the user releases the mouse, any shape that is wholly within the rectangle should be deleted.
Task 4.2
Add a free-hand drawing tool. When using this tool, moving the mouse with the button pressed should draw short lines or curves, as if a pen is being dragged across the screen. If the button is released, the program should stop drawing.
Task 4.3
Add the ability to select and delete a shape using the keyboard. How you select shapes, and how you enter and leave “keyboard delete” mode, is all up to you.
Task 4.4
Preview shapes as the user draws them. If the user has started to draw a shape, then you should show the shape currently being drawn using a hollow (not solid) rectangle, polygon, circle, ellipse, or sector. Lines will draw the same way as usual.
For polygons, you won’t be able to show a preview until two or more points have been saved.
Task 4.5
Allow the user to delete all shapes that have something in common. For example, all lines, all orange shapes, or all yellow rectangles. Whether you consider colour, shape, both, or something else as your measure of similarity is up to you. How the user selects what similarities to search for is also up to you.
Technical Report (COMP1100: 15 marks; COMP1130: 25 marks)
You should write a concise technical report explaining your design choices in implementing your program. The maximum word count is 1000 for COMP1100 students and 1500 for COMP1130 students. This is a limit, not a quota; concise presentation is a virtue.
Your report must be in PDF format, located at the root of your assignment repository on GitLab and named Report.pdf. Otherwise, it may not be marked.
The report must have a title page with the following items:
Your name
Your laboratory time and tutor Your university ID
Content and Structure
Your audience is the tutors and lecturers, who are proTcient at programming and understand most concepts. Therefore you should not, for example, waste words describing the syntax of Haskell or how recursion works. After reading your technical report, the reader should thoroughly understand what problem your program is trying to solve, the reasons behind major design choices in it, as well as how it was tested. Your report should give a broad overview of your program, but focus on the speciTcs of what you did and why.
Remember that the tutors have access to the above assignment speciTcation, and if your report only contains details from it then you will only receive minimal marks. Below is an potential outline for the structure of your report and some things you might discuss in it.
Introduction
If you wish to do so you can write an introduction. In it, give: A brief overview of your program:
how it works; and
what it is designed to do.
If you have changed the way the controls work, or added something that may make your program behave unexpectedly then it would be worth making a note of it here.
This section is particularly relevant to more complicated programs.
Content
Talk about why you structured the program the way you did. Below are some questions you could answer:
Program design
Describe what each relevant function does conceptually. (i.e. how does it get you closer to solving the problems outlined in this assignment spec?) How do these functions piece together to make the Tnished program? Why did you design and implement it this way?
What major design choices did you make regarding the functions that
you’ve written, and the overall structure of your program? Assumptions
Describe assumptions you have made about how a user might use the program, and how this has infuenced your design decisions.
Testing
How did you test individual functions?
Be speciTc about this – the tutors know that you have tested your program, but they want to know how.
Describe the tests that prove individual functions on their own behave as expected (i.e. testing a function with different inputs and doing a calculation by hand to check that the outputs are correct).
How did you test the entire program? What tests did you perform to show that the program behaves as expected in all (even unexpected) cases?
Again, be speciTc – did you check that you can draw shapes from left to right? What about right to left? An ellipse is deTned by the two opposite corners of a bounding box – did you check that it Tts perfectly within a rectangle drawn from the same two input points? Have you checked edge cases (this is a computer science term that refers to unexpected or unlikely inputs that may cause a program to crash or behave in strange ways)? It is not likely that someone would try to change the tool halfway through drawing a shape, but it is essential that it has behaviour deTned for that scenario. Describe similar tests that you have done to ensure the program can handle all inputs.
Inspiration / external content
What resources did you use when writing your program (e.g., published algorithms)?
If you have used resources such as a webpage describing an algorithm, be sure to cite it properly at the end of your report in a ‘References’ section. References do not count to the maximum word limit.
Refection
Discuss the reasoning behind your decisions, rather than what the decisions were. You can refect on not only the decisions you made, but the process through which you developed the Tnal program:
Did you encounter any conceptual or technical issues?
If you solved them, describe the relevant details of what happened and how you overcame them.
Sometimes limitations on time or technical skills can limit how much of the assignment can be completed. If you ran into a problem that you could not solve, then your report is the perfect place to describe them. Try to include details such as:
theories as to what caused the problem;
suggestions of things that might have Txed it; and
discussion about what you did try, and the results of these attempts.
What would you have done differently if you were to do it again
What changes to the design and structure you would make if you wrote the program again from scratch?
Are parts of the program confusing for the reader? You can explain them in the report (in this situation you should also make use of comments in your code).
If you collaborated with others, what was the nature of the collaboration? (Note that you are only allowed to collaborate by sharing ideas, not code.)
Collaborating is any discussion or work done together on planning or writing your assignment.
Other info
You may like to briefy discuss details of events which were relevant to your process of design – strange or interesting things that you noticed and Txed along the way.
Things to avoid in a technical report
Line by line explanations of large portions of code. (If you want to include a speciTc line of code, be sure to format as described in the “Format” section below.)
Pictures of code or VSCodium.
Content that is not your own, unless cited.
Grammatical errors or misspellings. Proof-read it before submission.
Informal language – a technical report is a professional document, and as such should avoid things such as:
Unnecessary abbreviations (atm, btw, ps, and so on), emojis, and emoticons; and
Stories / recounts of events not relevant to the development of the program.
Irrelevant diagrams, graphs, and charts. Unnecessary elements will distract from the important content. Keep it succinct and focused.
If you need additional help with report writing, the academic skills writing centre has a peer writing service and writing coaches.
Format
You are not required to follow any speciTc style guide (such as APA or Harvard). However, here are some tips which will make your report more pleasant to read, and make more sense to someone with a computer science background.
Colours should be kept minimal. If you need to use colour, make sure it is absolutely necessary.
If you are using graphics, make sure they are vector graphics (that stay sharp even as the reader zooms in on them).
Any code, including type/function/module names or Tle names, that appears in your document should have a monospaced font (such as Consolas, Courier New, Lucida Console, or Monaco)
Other text should be set in serif fonts (popular choices are Times, Palatino, Sabon, Minion, or Caslon).
When available, automatic ligatures should be activated.
Do not use underscore to highlight your text.
Text should be at least 1.5 spaced.
Communicating
Do not post your code publicly, either on Piazza or via other forums. Posts on Piazza trigger emails to all students, so if by mistake you post your code publicly, others will have access to your code and you may be held responsible for plagiarism.
Once again, and we cannot stress this enough: do not post your code publicly . If you need help with your code, post it privately to the instructors.
When brainstorming with your friends, do not share code. There might be pressure from your friends, but this is for both your and their beneTt. Anything that smells of plagiarism will be investigated and there may be serious consequences.
Sharing ideas and sketches is perfectly Tne, but sharing should stop at ideas. Course staff will not look at assignment code unless it is posted privately in piazza.
Course staff will typically give assistance by asking questions, directing you to relevant exercises from the labs, or deTnitions and examples from the lectures.
Submission Checklist
Once you have Tnished your assignment, and preferably 24 hours prior to the deadline, you should make sure that:
You have fully read and understand the entire assignment speciTcation.
Your work has been pushed to GitLab.
Your program compiles and runs, including the cabal v2-test test suite.
Your program works on the lab machines – if the program does not work on the lab machines, it might fail tests used by the instructors.
You have proof-read and spell-checked your report.
The report is in PDF format, located at the root of your project on GitLab and named Report.pdf. That capital R is important – Linux uses a case-sensitive Tle system. Otherwise, it may not be marked.
Updated: 06 Jun 2020
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