4RL

4RL (pronounced "for real") is an esoteric programming language created by User:Frogstair in April 2020, and is a breed of brainfuck.

The language can be compiled to brainfuck in a 1:1 relationship if the A command is not used.

Language overview

4RL, like brainfuck, operates on a tape, each cell in the tape is initialized to zero. The tape is 2^16 bytes long, each cell being one byte.

The commands are equivalent to brainfuck:

Command	BF equivalent	Result
4	+	Increment tape cell at pointer
r	-	Decrement cell pointer
e	>	Advance pointer to next cell
a	<	Retreat pointer to previous cell
l	[	If value under pointer is zero, jump to matching L
R	,	Take user input, store it in the cell under pointer
E	.	Output value under pointer as ASCII character
A	None	Terminate program
L	]	If value at pointer is not zero, jump to matching l

Examples

Hello, World!

Here is a hello world program

44444444le4444le44e444e444e4aaaarLe4e4eree4laLarLeeEerrrE4444444EE444EeeEarEaE444ErrrrrrErrrrrrrrEee4Ee44E

Cat Program

This cat program is repeated until the user inputs the null character:

RlERL

Truth-Machine

The following serves in the definition of a truth-machine:

RElrre4leeLalELaaL

Program Termination

This example demonstrates the program termination instruction A by printing the letter “B” once, but obviating its iterum output via an intermediate halt command:

444444444444444444444444444444444444444444444444444444444444444444
EAE

Interpreter

• Common Lisp implementation of the 4RL programming language.