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 theunsvgcrate.
• Handle various Logo commands for turtle control, variables, queries, conditionals, and math operations.
• Implement design excellence features for full marks.

• 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.

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

• The assignment uses theunsvgcrate to generate SVG or PNG images.
• unsvg::Imagerepresents an image and has methods likedraw_simple_line.
• unsvg::get_end_coordinatesreturns where a line drawn from a given point would end.

• Produce a program calledrslogothat 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 theunsvgcrate if there are no issues.

• 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 theunsvglibrary, or building a transpiler.
• Markers will consider a reasonable attempt at one of these tasks as sufficient.

• 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 includePENUP,PENDOWN,FORWARD,BACK,LEFT,RIGHT,SETPENCOLOR,TURN,SETHEADING,SETX,SETY.
• Turtle can go off the image without causing an error.

• Implement theMAKEcommand to create and assign variables.
• Implement theADDASSIGNcommand for variable increment.
• Support “queries” likeXCOR,YCOR,HEADING,COLOR.

• ImplementIF EQandWHILE EQcommands for conditional execution and looping.

• Implement operations in Polish Notation likeEQ,NE,GT,LT,AND,OR,+,-,*,/.
• Implement stack operations forIFandWHILE.

• Implement procedures analogous to functions in other languages.
• Procedures are defined with a line starting withTO, followed by the procedure name and arguments, and ending withEND.

• 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.

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

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

• See instructions at the bottom of the page.

• Can use crates from crates.io under certain conditions.

• Marked on Mechanical Style (10%), Functional Correctness (40%), and Idiomatic Design (50%).

• Assignment is individual.
• No joint work or sharing of code allowed.
• Use of code-synthesis tools is permitted but with caution.
• Submit work by running6991 give-crateby Week 7 Wednesday 17:00:00.