Hello today I am a unicorn
| Paradigm(s) | Imperative |
|---|---|
| Designed by | Hakerh400 |
| Appeared in | 2020 |
| Computational class | Turing complete |
| Major implementations | Interpreter |
| File extension(s) | .txt |
Hello today I am a unicorn is a Turing-complete programming language that has only two variables.
Overview
There are only two variables: x and y. Both are non-negative integers of unlimited size.
Source code consists of zero or more instructions. Any instruction can be prefixed by a label.
Each instruction begins with the variable name it uses (x or y), then operator that is applied and operands.
Operator Xor
Denoted by ~. No operands. Inverts the lowest bit of the variable. Example:
x~
Value of x before: 123
Value of x after: 122
Operator Shift left
Denoted by +. No operands. Performs binary shift to the left. Example:
y+
Value of y before: 5
Value of y after: 10
Operator Shift right
Denoted by -. No operands. Performs binary shift to the right. Example:
x-
Value of x before: 15
Value of x after: 7
Operator If
Denoted by ?. Two operands (and they are labels). If the lowest bit is 1 jump to the first label, otherwise jump to the second label. Example:
y? label1 label2 label1: x+ label2: x-
If y is odd, x will be shifted left and then shifted right. If y is even, x will only be shifted right.
Note: all instructions except this simply increment instruction pointer.
I/O format
Input is a non-negative number. It is written in the x variable before program starts, while y is initially 0. When program terminates, y contains the output.
Examples
Cat
Note: assuming the same I/O format as described here for converting from/to ASCII strings.
x? copy exit
copy: x- y+ y~ y+
x? flip next
flip: y~
next: x- x? copy exit
exit: x~
Computational class
The variables x and y effectively implement two stacks of bits; you can push to these via a left-shift (possibly followed by an xor), pop them via a right-shift, and test the bottom bit via the if operator. Because the language also allows arbitrary control flow, this allows two-stack machines to be implemented more or less directly (a two-counter machine can also be implemented via treating the counter as a stack of multiple 0 bits above a single 1 bit), making the language Turing complete.