PATH

PATH, invented by Francis Rogers in August 2003, is a two-dimensional language inspired by Brainfuck and Befunge. PATH's environment, like Brainfuck's, consists of an array of memory cells all initialized to zero and character-based standard input and output. PATH understands the following commands:

As in Brainfuck, any character not understood as a command is simply skipped over.

Computational class
We can show how to convert any Brainfuck program into an equivalent PATH program, and in this way, show that PATH is in the same computational class as Brainfuck (i.e. that it is Turing-complete).

Consider the following trivial Brainfuck program:

+[>-<-]

and  remain unchanged. and  become   and   respectively. Finally, each  loop can be coded idiomatically, using   commands. This is spaced out for clarity in the following example:

/ v         \ + /!\  }-{-  v!\ \         /

Variations
Some implementations have added ] and [ to unconditionally direct the flow of the program right or left, but the PATH author has requested these implementors give their variants different names.

Languages based on PATH include SNUSP, which is more orthogonal and optionally supports advanced features, and LNUSP, which uses only 5 commands and supports diagonal control flow.

External resources

 * Official PATH site with interpreter
 * A javascript implementation of the interpreter