COMP6991 Rust Logo Interpreter Assignment

Logo Language Overview

Logo is a programming language derived from Lisp and others.

Older programmers often had their first programming experience with Logo.

Key feature is a “turtle” for drawing by picking up and putting down a pen and moving around.

Assignment Goals

Practice designing and structuring a larger Rust program. Focus on modern programming skills and design patterns.

Have fun creating an aesthetic and interesting application while connecting with programming

history.

Assignment Requirements

Build a Logo interpreter that writes to an.svg or.png image using the unsvg crate.

Handle various Logo commands for turtle control, variables, queries, conditionals, and math operations.

Implement design excellence features for full marks.

1. Introduction to the Logo Language

   Tokens

   A token can be a procedure (like a function), a variable (prefixed by : ), or a value (prefixed by

   ” ).

   Procedures always take a fixed number of arguments.

   Values in Logo are always strings, but some like “TRUE” and “FALSE” are interpreted as booleans and some can be parsed as numbers.

   Program Structure

   A logo program consists of lines of text split into tokens by whitespace. Lines starting with // or empty lines are ignored as comments.

2. Introduction to Unsvg

   The assignment uses the unsvg crate to generate SVG or PNG images.

   unsvg::Image represents an image and has methods like draw_simple_line .

   unsvg::get_end_coordinates returns where a line drawn from a given point would end.

3. How Your Program Will Work

   Produce a program called rslogo that takes four arguments: a logo program file (.lg), the output SVG/PNG file path (.svg or.png), image height, and image width.

   Read the logo program, parse and execute it line by line.

   Exit with a non-zero return code and print an error message if there’s an issue. Write an SVG or PNG using the unsvg crate if there are no issues.

4. Design Excellence

   Options for design excellence include making beautiful errors, achieving 80% test coverage, using a parser combinator library, creating a facility for language extensions, building a zero-copy program, contributing to the unsvg library, or building a transpiler.

   Markers will consider a reasonable attempt at one of these tasks as sufficient.

5. The Tasks To Complete

   Part 1: Turtle Control (20%)

   Control the “turtle” which is like an invisible pen that can draw on the image. Turtle starts “up” (not drawing) in the center of the screen facing straight up.

   Commands include PENUP , PENDOWN , FORWARD , BACK , LEFT , RIGHT , SETPENCOLOR , TURN ,

   SETHEADING , SETX , SETY .

   Turtle can go off the image without causing an error.

   Part 2: Variables and Queries (20%)

   Implement the MAKE command to create and assign variables. Implement the ADDASSIGN command for variable increment.

   Support “queries” like XCOR , YCOR , HEADING , COLOR .

   Part 3: IFs, WHILE, [ ] (20%)

   Implement IF EQ and WHILE EQ commands for conditional execution and looping.

   Part 4: Implementing Maths and Comparisons using a Stack (20%)

   Implement operations in Polish Notation like EQ , NE , GT , LT , AND , OR , + , – , * , / . Implement stack operations for IF and WHILE .

   Part 5: Logo Defined Procedures (20%)

   Implement procedures analogous to functions in other languages.

   Procedures are defined with a line starting with TO , followed by the procedure name and arguments, and ending with END .

6. Common Questions

   Design Approaches

   Line-by-line approach: Execute each line in turn while storing more data and state.

   Parse then execute approach: Convert the text into an Abstract Syntax Tree and read from it.

   Planning

   A happy middle is suggested: think about the approach and read through the assignment without spending more than 30 minutes planning.

   Using AI

   Permitted uses of AI include seeking help with concepts, pattern matching, generating skeletons, and writing tests.

7. Other Information

Submission

See instructions at the bottom of the page.