Dubbelweal

Dubbelweal is a two-dimensional turning tarpit by User:ChuckEsoteric08.

Description

The language works on a right-infinite tape which stores a single base-4 digit, from 0 to 3. It has two wheels, instruction wheel which is manipulated by the code and tape wheel which is manipulated by the instruction wheel. There are two types of commands: @ and everything else. If a character other than @ is executed it advances the instruction wheel once. If @ is executed it executes instruction on the instruction wheel. Instruction wheel has following commands:

• turn - turn instruction pointer 45 degrees clockwise times equal to the value of a current cell (0 will not turn instruction pointer at all).
• rot - rotates the Tape Wheel once.
• exec - executes instruction at the tape wheel.

Tape wheel has following commands:

• right - move tape pointer right.
• left - move tape pointer left.
• inc - increment current cell, wrapping around to 0 if it was 3.
• out - output current cell's value as an integer
• inp - input a single 4-bit digit into the current cell

As can be seen, it is fully reversible.

Computational class

Dubbelweal is Turing-complete as it can simulate 1-bit Reversible Brainfuck (translation from Quaternary Reversible Brainfuck would be much more difficult). Program consist of instructions translated as concatenated horizontal patterns.

• > becomes:

--@--@@@@@--

• < becomes:

-@-@--@@@@--

• + becomes:

-@@-@--@@@---@@-@--@@@--

• . becomes:

-@@@-@--@@--          

• , (with 1 being encoded as 2) becomes:

-@@@@-@--@--

• [ becomes:

---@@---
   ||
   ||   
  @++---
  @@@---

• ] becomes:

---@---
   |
   |
---+@
---@@

For each new nesting depth gap between first and second lines should be increased by three.

See also

• 1L
• Wunnel