LstackG

The title of this article is not correct because of technical limitations. The correct title is actually <stack>.

<stack>

Paradigm(s)	imperative
Designed by	None1
Appeared in	2023
Memory system	Stack-based
Dimensions	one-dimensional
Computational class	Push-down automata
Reference implementation	C++, JavaScript
Influenced by	Brainfuck
File extension(s)	.lsg

<stack> is an esolang created by User:None1. It's very brainfuck-like. However, it's not Turing complete.

Opcodes

There are only 7 valid opcodes in <stack>, which are <,s,t,a,c,k,and >, other characters are ignored. <stack> is case sensitive.

Execution

Just like its name, <stack> is stack-based, and the stack contains only 8-bit integers (bytes).

In the beginning, there is an initial 0 in the stack, and each opcode does something to the stack:

< If the the top of the stack is zero, move to the matching >, otherwise just move to the next character.

s Pushes a 0 into the stack.

t Reads a character from the standard input, and pushes its ASCII value into the stack.

a Adds 1 to the top of the stack, when the result is 256, it becomes 0 to fit in a byte.

c Print the top of the stack to standard output as a character, then pop it, does nothing if the stack contains less then 2 elements.

k Pops from the stack once, does nothing if the stack contains less then 2 elements.

> If the top of the stack is not zero, move to the matching <, otherwise just move to the next character.

It's obvious that the stack NEVER becomes empty.

Translate to Brainfuck

Any <stack> code can be translated to Brainfuck using the table below, but the opposite is not true.

<stack>   Brainfuck
(begin)   >+>
<         <<[>>
s         >>
t         ,>>
a         <<+>>
c         >+<-<-[>+<<.[-]->>]-[+>-]+<<+>>[->+]
k         <[>>]<
>         <<]>>

Example Programs

Hello World program (very long!):

saaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaacsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaacsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaac

Cat program (never terminates):

a<tc>

Reverse one line of input:

taaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaa<taaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaa>k<aaaaaaaaaac>

Reads text, prints <stack> code that prints it:

a<saaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaact<aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaasaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaac>aaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaac>

The name of this language is also considered an example program, which does nothing.

Existence of a quine

Does <stack> have a non-empty quine? The answer is probably no, but I (User:None1) can't prove it.

The content here should be changed if someone proves that a <stack> quine exists or not.

External Resources

Webpages

• GitHub repository of <stack>
• The webpage of <stack>

Offline Interpreters

• An interpreter in C++, written by the creator of this language (User:None1). as Windows executable (64 bit)
• An interpreter in JavaScript which uses non-interactive I/O, also written by User:None1.

Online Interpreters

• <stack> playground, where you can run <stack> code directly online.