tinybf

A minuscule interpreter for the Brainfuck programming language, written in Ruby.

Features

• Matches and caches brackets before executing code, speeding up the interpretation.
• Has an array of unsigned single-byte cells that can grow "infinitely" to the right.
• Wraps cell values if they exceed the minimum (0) or maximum (255).
• Ignores a < command if the array pointer is on the left-most cell.
• Passes Daniel Cristofani's tests and follows his Epistle to the Implementors.
• Weighs only 328 bytes!

Usage

Apart from the eight standard Brainfuck commands, the first exclamation mark (!) is a delimiter used to separate the interpreted code from its standard input (stdin).

Here's a usage example with Daniel Cristofani's numwarp.b:

$ ruby tinybf.b
>>>>+>+++>+++>>>>>+++[>,+>++++[>++++<-]>[<<[-[->]]>[<]>-]<<[>+>+>>+>+[<<<<]<+>>[
+<]<[>]>+[[>>>]>>+[<<<<]>-]+<+>>>-[<<+[>]>>+<<<+<+<--------[<<-<<+[>]>+<<-<<-[<<
<+<-[>>]<-<-<<<-<----[<<<->>>>+<-[<<<+[>]>+<<+<-<-[<<+<-<+[>>]<+<<<<+<-[<<-[>]>>
-<<<-<-<-[<<<+<-[>>]<+<<<+<+<-[<<<<+[>]<-<<-[<<+[>]>>-<<<<-<-[>>>>>+<-<<<+<-[>>+
<<-[<<-<-[>]>+<<-<-<-[<<+<+[>]<+<+<-[>>-<-<-[<<-[>]<+<++++[<-------->-]++<[<<+[>
]>>-<-<<<<-[<<-<<->>>>-[<<<<+[>]>+<<<<-[<<+<<-[>>]<+<<<<<-[>>>>-<<<-<-]]]]]]]]]]
]]]]]]]]]]]]>[>[[[<<<<]>+>>[>>>>>]<-]<]>>>+>>>>>>>+>]<]<[-]<<<<<<<++<+++<+++[[>]
>>>>>>++++++++[<<++++>++++++>-]<-<<[-[<+>>.<-]]<<<<[-[-[>+<-]>]>>>>>[.[>]]<<[<+>
-]>>>[<<++[<+>--]>>-]<<[->+<[<++>-]]<<<[<+>-]<<<<]>>+>>>--[<+>---]<.>>[[-]<<]<]
!1337
^D
      /\
        \
    /\
     /\
  /\  /
   /\
 \  /
  \

In the example above, 1337 is the input to the interpreted program and ^D stands for pressing Ctrl-D.

Limitations

• Very slow compared to a C implementation
• No error checking (e.g. unmatched brackets)
• Both the interpreted source code and its input are passed through the same stream (standard input). This makes I/O non-interactive.
• Unsurprisingly, the code is obfuscated and a bit hard to read. That said, here's a list of what each variable is:
  • c is a String holding the code and b its pointer
  • i is a String holding the input and h its pointer
  • a is an Array holding the memory and z its pointer
  • j is a Hash used to cache the position of brackets and s an Array used (as a stack) to build it

License

The MIT License

Author

Angelos Orfanakos, https://agorf.gr/