bf-rs

Optimizing Brainf*** interpreter written in Rust

• Unlimited number of memory cells are available
• Memory cell increments and decrements wrap around

Usage

You need Rust and Cargo installed to build this. Clone this repository and build.

$ cargo build --release

Run any program

$ target/release/bfrs samples/mandelbrot.bf

or simply

$ cargo run --release samples/mandelbrot.bf

Interactive Mode

You can also run the interpretor in interactive mode.

• dump command will dump the current memory state in a hd like format
• reset command will reset the internal memory state

$ cargo run --release
>>> dump
-----------
Memory Dump
-----------
00000000  00                                                |.               |
00000010

>>> [-][Following will print capital 'A' followed by a new line character]
>>> ++++++++[>++++++++<-]>+.>++++++++++.
A

>>> dump
-----------
Memory Dump
-----------
00000000  00 41 0a                                          |.A.             |
00000010

>>> [-][use 'reset' command to reset memory state]
>>> reset

>>> dump
-----------
Memory Dump
-----------
00000000  00                                                |.               |
00000010
>>> 

Optimizations

The interpretor makes some optimizations inspired by the excellent bfc project.

1. Combine successive additions and subtractions i.e. +++- is done in a single step as increment 2

2. Combine successive memory cell pointer increment and decrement i.e. >>>< is done in a single step as shift right twice

3. The biggest performance gain over the naive implementation was caching the loop start and end index so that input file is scanned only once.

Tests and benchmarks

Some fairly comprehensive tests are availabel in tests/.

$ cargo test --release

To run benchmarks

$ cargo bench

License

Licensed under GPLv3. Sample programs are largely written by other authors and are under other licenses.