An interpreter for brainfuck, written in whitespace.
More specifically, the interpreter is written in an ASM-like language that compiles 1-to-1 into a Whitespace program. You can find the original source code in bf.wsasm. Compilation is handled by whitespace-rs, so if you have it installed, you can compile it as follows:
$ wsc -t -m -f asm bf.wsasm >bf.ws
The resulting program can be executed using the same tool:
$ wsc --unchecked-heap bf.ws
The program is read from STDIN until a ! character is encountered, after which all bytes will be considered input to the program.
$ echo '+++[->,+.<],.!foo' | wsc --unchecked-heap bf.ws
gpp
The version of BF simulated by this interpreter has an unbounded number of 8-bit cells to the right. Moving left of the starting cell doesn't work.