XRF
XRF is a stack-based esoteric programming language designed by User:Scoppini in 2015.
Overview
XRF operates on a stack of nonnegative integers of arbitrary size, which is initialized with a single 0 value. XRF programs are divided into 5-command "chunks", which are separated by whitespace. Execution begins with the first chunk. When the end of a chunk is reached, the program moves on to the chunk corresponding to the top value of the stack, where the first chunk corresponds with 0. The commands are:
| Command | Description |
|---|---|
| 0 | Push a byte of user input onto the stack |
| 1 | Output the top value of the stack as an ASCII character, popping it |
| 2 | Pop the stack |
| 3 | Duplicate the top of the stack |
| 4 | Swap the two top values of the stack |
| 5 | Add one to the top value of the stack |
| 6 | Subtract one from the top value of the stack |
| 7 | Replaces the top two values of the stack with their sum |
| 8 | Ignore the next command if this chunk has not been visited previously |
| 9 | Send the top element of the stack to the bottom |
| A | Jump to the next chunk early ('next' determined by the top value of the stack, as usual) |
| B | Terminates the program |
| C | Ignore the next command if this chunk has already been visited previously |
| D | Randomizes the order of the stack |
| E | Replaces the top two values of the stack with the absolute value of their difference (abs(topmost - 2nd_topmost)) |
| F | Nop |
All characters other than 0123456789ABCDEF are not allowed and will cause an error.
Examples
Hello, World! program
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Cat program
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Truth-machine
Random generator
A program that generates random output consisting of characters '0' and '1'. Never terminates.
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Quine
Here: http://yiap.nfshost.com/esoteric/xrf/quine.xrf This quine is large (~280kb) and extremely slow if run on the original Python interpreter. In fact, a faster interpreter was written in C to allow the program to be run (the quine's author let it run for four hours before understanding that a faster solution was needed).
An alternative interpreter
For running larger, time and memory consuming programs, one might use XRFaster, an interpreter written in C and designed to be fast. However, this particular interpreter does not implement XRF fully; commands 0, 8, C, and D are not implemented because they do not appear in the quine for the sake of which this interpreter was written in the first place. Neither does it perform any error-checking, so your programs need to be perfectly valid.