bf-hs

A Brainfuck interpreter written in Haskell.

Overview

bf-hs is a simple and efficient Brainfuck interpreter that can execute Brainfuck programs from files or standard input. Brainfuck is an esoteric programming language with only eight commands, making it a fun challenge to implement and an interesting way to explore language interpreters.

Features

• Complete Brainfuck language support with all 8 commands
• 30,000-cell memory tape (standard Brainfuck specification)
• Wraparound pointer arithmetic for safe memory access
• Interactive input/output support
• Read programs from files or standard input
• Clean, readable Haskell implementation

Brainfuck Commands

Command	Description
>	Move the data pointer to the right
<	Move the data pointer to the left
+	Increment the byte at the data pointer
-	Decrement the byte at the data pointer
.	Output the byte at the data pointer as an ASCII character
,	Input a byte and store it at the data pointer
[	Jump forward to the command after the matching ] if the byte at the data pointer is zero
]	Jump back to the command after the matching [ if the byte at the data pointer is nonzero

Installation

Prerequisites

• GHC (Glasgow Haskell Compiler)
• Cabal build system

Building from Source

1. Clone the repository:

   git clone https://github.com/grapefizz/bf-hs.git
   cd bf-hs

2. Build the project:

   cabal build

3. Install the executable:

   cabal install

Usage

Running a Brainfuck Program from a File

bf-hs program.bf

Running a Brainfuck Program from Standard Input

echo ">++++++++[<+++++++++>-]<." | bf-hs

or

bf-hs < program.bf

Example

The repository includes a sample "Hello World" program in hello.bf:

bf-hs hello.bf

This should output: Hello World!

Example Programs

Hello World (hello.bf)

>++++++++[<+++++++++>-]<.
>++++[<+++++++>-]<+.
+++++++..
+++.
>>++++++[<+++++++>-]<++.
------------.
>++++++[<+++++++++>-]<+.
<.
+++.
------.
--------.
>>>++++[<++++++++>-]<+.

Simple Addition

,>,<[->+<]>.

This program reads two single-digit numbers and outputs their sum.

Implementation Details

• Memory Model: Uses a 30,000-cell tape implemented with Haskell's IOUArray
• Pointer Wrapping: Implements wraparound arithmetic to prevent segmentation faults
• Loop Matching: Efficient bracket matching algorithm for [ and ] commands
• I/O Handling: Immediate character output with buffer flushing for responsive interaction

Development

Project Structure

bf-hs/
├── app/
│   └── Main.hs          # Main interpreter implementation
├── bf-hs.cabal          # Cabal package configuration
├── hello.bf             # Example Brainfuck program
├── LICENSE              # MIT License
├── CHANGELOG.md         # Version history
└── README.md            # This file

Dependencies

• base: Core Haskell library
• array: For efficient mutable arrays

License

This project is licensed under the MIT License - see the LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Acknowledgments

• Inspired by the original Brainfuck language created by Urban Müller
• Built with the excellent Haskell ecosystem