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Faust

An Interpreter for a Diabolical Language

Just in case you haven't had your fill of brainf***, here's my humble interpreter. It's fast enough for practical use, but is still a WIP. A few more levels of optimization and support for other brainf*** are in the works.

So far there are a few things that I'm quite pleased with:

  • It contains a benchmarking macro that was hard-won from studying the esoteric macro language within rust.
  • It doesn't use much recursion or nesting, so it is stack-safe, even with very large brainf*** programs.
  • It executes code from both files and user input.

Erik Bosman's infamous mandelbrot.b pushes interpreters to their limit. The sheer complexity is a ripe target for optimizations, and in fact the program was written with significant help in the form of a higher-level brainf***.

benchmark! results in release mode

  • Once upon a time, mandelbrot.b interpreted character-by-character took 26956892 milliseconds (7.5 hours) to finish.
  • mandelbrot.b takes only 26767 milliseconds (27 seconds) after a commit which condenses repeated commands together.
  • Currently, mandelbrot.b takes only 17247 milliseconds (17 seconds), thanks to optimizing the decoding order a little bit; [-] appears much less often than [ and ]. The reason this change is so effective is that interpreters make cpu branch prediction difficult, so correctly ordering the short-circuiting is an effective way to compensate.

Goals

My primary goal is to execute mandelbrot.b within 10 seconds using only code transformations.

A secondary goal is to support the many variants of brainf*** using frontends defined in a YAML file. Among the smaller goals is support for brainf*** synonyms such as Ook!. An interactive debugger and some threading support would be awesome.

With the knowledge this project brings, I hope to make a toy language and other potentially useful interpreters.

Cloning

If you use git

mkdir foo
cd foo
git clone https://github.com/Aarowaim/faust.git

If not, no worries

Download the repository from github as a zip and extract it to a folder

Building

Cargo

  • Go to the folder above src. Then type cargo build --release in a terminal at that folder.
  • You may now run using cargo run --release followed by an optional file containing brainf*** code. If no arguments are given you will later be prompted for a line of input to be executed as brainf*** code.
  • Run any of the examples from the example folder by calling cargo run --release examples\<filename>. To run mandelbrot, which will be my benchmark, the command is cargo run --release examples\mandelbrot.b. Try running rot13.b or sierpinski.b if you don't want to wait so long.

I don't use cargo

  • rustc src\main.rs will produce a target directory containing the executable faust_brainfuck.
  • Executing faust_brainfuck with filepath as a terminal argument will run that file