meowlang

Meowlang is an esoteric programming language designed for cats.

Online Interpreter

Visit the online interpreter.

Run from Source Code

Setup

yarn

Command-line Interpreter

Run a Meow program:

node . -i examples/hello.meow

node . -i examples/fibonacci.meow

Turn on debug info when running a Meow program:

node . -i examples/fibonacci.meow -d

Web-based Interpreter

Start a local server with

yarn start

Examples

Print the Fibonacci numbers with cat emojis:

The Fibonacci source code in English Meow:

MeowMeowMeowMeowMeowMeowMeowMeow;
MeowMeowMeowMeow;
Meow;
Meow;
MeowMeow;
MeowMeowMeowMeowMeowMeowMeowMeowMeowMeow;
MeowMeowMeowMeow;
MeowMeow;
Meow;
;
MeowMeowMeow;
MeowMeowMeowMeow;
MeowMeow;
MeowMeowMeowMeow;
MeowMeowMeow;
MeowMeowMeowMeowMeowMeow;
MeowMeowMeowMeow;
MeowMeowMeow;
MeowMeowMeowMeowMeow;
MeowMeow;
MeowMeowMeow;
MeowMeowMeowMeowMeow;
MeowMeowMeow;
MeowMeowMeow;
MeowMeow;
Meow;
MeowMeowMeowMeowMeowMeowMeow;
MeowMeowMeowMeowMeowMeowMeowMeowMeow;
MeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeowMeow;
MeowMeowMeowMeowMeowMeowMeowMeow;
MeowMeowMeowMeowMeowMeow;
MeowMeowMeow;
MeowMeowMeowMeowMeowMeowMeowMeowMeowMeow;

The Fibonacci source code in Chinese Meow:

喵喵喵喵喵喵喵喵;
喵喵喵喵;
喵;
喵;
喵喵;
喵喵喵喵喵喵喵喵喵喵;
喵喵喵喵;
喵喵;
喵;
;
喵喵喵;
喵喵喵喵;
喵喵;
喵喵喵喵;
喵喵喵;
喵喵喵喵喵喵;
喵喵喵喵;
喵喵喵;
喵喵喵喵喵;
喵喵;
喵喵喵;
喵喵喵喵喵;
喵喵喵;
喵喵喵;
喵喵;
喵;
喵喵喵喵喵喵喵;
喵喵喵喵喵喵喵喵喵;
喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵喵;
喵喵喵喵喵喵喵喵;
喵喵喵喵喵喵;
喵喵喵;
喵喵喵喵喵喵喵喵喵喵;

Language Specification

Meow List

A valid Meowlang program is simply a text representation of a Meow List.

A Meow List is a sequence of Meow elements.

Every Meow element contains zero or more Meow tokens. The number of Meow tokens in a Meow element corresponds to a non-negative integer value, which is the value of the Meow element.

A Meow element can be treated either as a Meow instruction or a Meow operand, depending on the execution context:

• When a Meow element is treated as a Meow instruction, the value of the element is the opcode of the instruction.
• When a Meow element is treated as a Meow operand, the operand value is the value of the element.

In the Meowlang runtime, the loaded Meow List is a read/write list, which is both a list of Meow instructions, and the only in-memory data structure that Meow instructions can access.

In other words, code is data and data is code.

Meow Tokens

A Meow token is a cat cry in plain text. The following Meow tokens are valid and interchangeable in Meowlang programs.

• Meow in English
• Miaou in French
• 喵 in Chinese
• Miao in Chinese Pinyin
• Miau in German
• ニャー in Japanese Katakana (Katakana because its onomatopoeia)

Meow tokens are case-insensitive. For example, Meow, meow, and MEOW are the same things.

Meow File Format

The text representation of a Meowlang program uses semicolon ";" to end every Meow element.

For example, the following code contains 5 Meow elements, whose values are 0, 1, 2, 3 and 4.

;
Meow;
Meow Meow;
Meow Meow Meow;
Meow Meow Meow Meow;

White spaces including " ", "\t" and "\n" are used for formatting purposes only, and will be ignored when the program is executed. You may layout your code in many different and interesting ways. For example, the following code is an equivalent representation of the above code:

; M e o w ; MeowMeow ; MeowMeowMeow ; MeowMeowMeowMeow ;

The Meow tokens in the supported languages can be mixed up in a same program. For example:

;
喵;
Meow Miao;
Miaou Miaou Miaou;
Miaou 喵 Meow Miao;

The preferred file extension of the Meow file format is ".meow".

Simplified Meow File Format

A Meow program can also be stored and loaded as a sequence of non-negative integer numbers, each number corresponding to the value of a Meow element. For example:

0
1
2
3
4

The preferred file extension of the simplified Meow file format is ".smeow".

Meow Instruction Set

Opcode	Name	Description	IP Operation
0	RET	Print an empty line "\n" to the output console.	IP++
1	MEOW	Print T cat emoji characters to the output console.	IP++
2	PUSH	Push N to the tail of the Meow List.	IP += 2
3	POP	Pop the tail element from the Meow List.	IP++
4	LOAD	Push the value of E(N) to the tail of the Meow List.	IP += 2
5	SAVE	Copy the value of the tail element to E(N).	IP += 2
6	ADD	Add the values of the last two tail elements, pop them from the tail, then push the result to the tail.	IP++
7	SUB	Subtract the value of the last element from the value of the second to the last element, pop the last two elements from the tail, then push the result to the tail. If the result is negative, a zero is pushed.	IP++
8	JMP	Set IP to N.	IP = N
9	JE	If the value of the tail element is zero, set IP to N. Otherwise, continue to execute the next after the next instruction.	IP = (T == 0) ? N : IP + 2
>=10	NOP	No operation.	IP++

• IP: The Instruction Pointer.
• T: The value of the tail element.
• N: The value of the next element.
• E(N): The element indexed by the value of the next element.