weebasic

Toy BASIC-like language and interpreter implemented in Rust for study or interview purposes. The interpreter is intentionally left incomplete so that new features can be implemented as coding exercises. This software is distributed under the Unlicense, meaning it is effectively public domain, though crediting the author is appreciated.

Design:

• Top-down recursive descent parser
• The tokenizer is built directly into the parser
• Stack-based bytecode interpreter
• No operator precedence for simplicity
• No garbage collector

Interview Format

The first thing you should do is to clone this repository and create your own branch, eg git checkout -b yourusername. I would then suggest browsing the code and the example source files to get familiar with them a little bit. I'm going to ask you to implement new features in weebasic. For example, I might ask you to implement new syntactic constructs or to add support for new data types in the language. You should try to install rustc and compile weebasic before the interview if possible

The primary purpose is to evaluate your knowledge of Rust and systems programming, and to see if you understand how a simple parser and bytecode interpreter works. I'm also assessing your communication and problem-solving skills. You should try to roughly explain what you are doing as you do it.

You'll be doing the coding, but I'm here to help you. I'm a friendly interviewer and my goal is to help you succeed. The interview isn't designed to cause you stress. Your solution doesn't need to be perfect and you don't need to worry about performance. Typically, the simplest viable solution is the expected answer. You're allowed to ask as many clarifying questions as you want during the interview, and you're also allowed to use Google if you need to. It's very much expected that you might need to look up Rust documentation, for example.

Installation

Requirements:

• The rust compiler (rustc)
• No other dependencies

Clone this repository:

git clone https://github.com/maximecb/weebasic.git

To build weebasic:

cd weebasic
rustc weebasic.rs

To test that weebasic is working correctly:

./weebasic tests.bas

Usage

For syntax examples, see example.bas and tests.bas.

To execute programs, run:

./weebasic example.bas

Debugging Tips

To get a backtrace, you can set the RUST_BACKTRACE environment variable:

RUST_BACKTRACE=1 ./weebasic example.bas

You can also set the RUST_LOG environment variable to see debug! outputs:

RUST_LOG=debug ./weebasic example.bas