Note: This project has been abandoned because i don't have the time to work on it, it was a cool project for learning though.
Meow is a simple language im making in C# as a side project written completely from scratch, i use a regex lexer and then generate an AST which i then walk through for execution, you can download the meow playground here.
example script.
add = function(a: number, b: number): number {
return a + b;
}
result: number = add(5, 3);
print(result); // 8without type hinting (type hints are not enforced)
add = function(a, b) {
return a + b;
}
result = add(5, 3);
print(result); // 8Generated AST
{
"Statements": [
{
"Identifier": "add",
"Value": {
"FunctionNodes": [
{
"ReturnValue": {
"Expression": "+",
"InBracket": false,
"Left": {
"Identifier": "a"
},
"Right": {
"Identifier": "b"
}
}
}
],
"parameters": [
"a",
"b"
]
}
},
{
"Identifier": "result",
"Value": {
"Identifier": "add",
"Arguments": [
{
"Literal": 5.0
},
{
"Literal": 3.0
}
]
}
},
{
"Identifier": "print",
"Arguments": [
{
"Identifier": "result"
}
]
}
]
}this code executes the same as previous one
the language is a semicolon based language, i have some error checking for semicolons so if you don't include them you may start getting logic errors.
variables are declared like x = 2 or with type hinting x:number = 2 these are all currently global, there is no local variables yet, the types are not enforced but are just there for clarity and documentation.
function calls via C# side print("hello world!") using delegate called MeowFunction for interacting with C# side, supports arguments in the form of object[], it also has the script as context and a return type in the form object
functions are declared as variable = function() {}, the functions are treated as first class citizens.
The if-else statements and while statements work, you cannot chain elifs yet, there is no for statements yet but you could make that with a while loop and a variable.
it comes with some basic functions, print, input, wait, int, number, string, if and type
the program calls the function update every frame if it can find one. (this was for testing)
setting a function as a variable and calling it
betterPrint: function = print;
betterPrint("Hello world!");calling an anonymous function
call = function(func: function): void {
func();
}
// calls the anonymous function, prints hello world!
call(function() {
print("hello world!");
});returning a function
returnFunc = function(): function {
return function() {
print("hello world!");
}
}
func: function = returnFunc();
func(); // prints hello world!current if functions (bound to change)
if(true) {
print("condition was true!");
} else {
print("condition was false!");
}this is an example script using some of the basic functions.
name: string = input("What is your name? ");
print("hello", name);the AST for this simple program.
{
"Statements": [
{
"Identifier": "name",
"Value": {
"Identifier": "input",
"Arguments": [
{
"String": "What is your name? "
}
]
}
},
{
"Identifier": "print",
"Arguments": [
{
"String": "hello"
},
{
"Identifier": "name"
}
]
}
]
}more complex programs that rely on type hinting everywhere.
add = function(a: number, b: number): number {
return a + b;
}
print("the add game, can you get over the limit?");
limit: number = number(input("set the limit. "));
number1: number = number(input("give me the first number. "));
number2: number = number(input("give me the second number. "));
result: number = add(number(number1), number(number2));
if(result > limit) {
print("you won");
} else {
print("you lost.");
}
print("total sum you got was", result, "you got", result - limit, "greater than", limit);simple program for showing if-elses and a while loop.
while (true) {
x = input("what do you want to try? true, false or exit? ");
if (x == "exit") {
// exits the program returns a value for c# runner, intended behaviour
return;
}
if (x == "true") {
print("got it true");
} else {
print("its false");
}
}a custom application that loops how many times the user inputted
forLoop = function(to: number, loop: function): void {
i = 0;
while (i < int(to)) {
loop(i);
i = i + 1;
}
}
howManyCount: string = input("how do you want it to count? ");
forLoop(int(howManyCount), function(i: number) {
print(i + 1);
});an actual game where you have to reach the end in the minimum amount of attempts, you play as a O
// variables
playerX: number = 0;
playerY: number = 0;
gridSizeX: number = 10;
gridSizeY: number = 20;
goalPosX: number = gridSizeX - int(gridSizeX / 2);
goalPosY: number = gridSizeY - int(gridSizeY / 2);
attempts: number = (gridSizeX + gridSizeY) / 2;
print("get to the middle! with only", attempts,"movements.");
getInputs = function(): void {
move = input("where do you want to move? w = up, s = down, a = left and d = right. ");
if (move == "w") {
playerY = playerY - 1;
playerY = int(playerY);
if (playerY < 0) {
playerY = 0;
}
attempts = attempts - 1;
}
if (move == "s") {
playerY = playerY + 1;
playerY = int(playerY);
if (playerY > (gridSizeX - 1)) {
playerY = gridSizeX - 1;
}
attempts = attempts - 1;
}
if (move == "a") {
playerX = playerX - 1;
playerX = int(playerX);
if (playerX < 0) {
playerX = 0;
}
attempts = attempts - 1;
}
if (move == "d") {
playerX = playerX + 1;
playerX = int(playerX);
if (playerX > (gridSizeY - 1)) {
playerX = gridSizeY - 1;
}
attempts = attempts - 1;
}
}
drawBoard = function(): void {
x = 0;
while (x < int(gridSizeX)) {
concatenatedLine = "";
y = 0;
while (y < int(gridSizeY)) {
if (playerX == y and playerY == x) {
concatenatedLine = concatenatedLine + "O";
} else {
if (x == goalPosX and y == goalPosY) {
concatenatedLine = concatenatedLine + "&";
}else {
concatenatedLine = concatenatedLine + "'";
}
}
y = y + 1;
y = int(y);
}
print(concatenatedLine);
x = x + 1;
x = int(x);
}
}
drawBoard();
while (true) {
print("you have", attempts, "attempts left");
getInputs();
drawBoard();
// i flipped it so it may look wrong but its correct
if (playerY == goalPosX and playerX == goalPosY) {
print("you have won the game!");
return;
}
if (attempts == 0) {
print("you have ran out of attempts!, you have lost the game.");
return;
}
}I plan on making it a language similar to python, lua and javascript with hints of miniscript to create a scripting language. Maybe i plan on generating bytecode in the distant future, but rn im walking through ASTs.
I am making this as a side project for fun and i love doing it
to embed meow in your C# scripts, you need to create a new Script, then you can register all the globals you want, so for example you can register a function call for printing and then you just run the script via DoString, it takes in 1 argument which is the script content, heres an example script, currently its not unity friendly because im using some of the new c# features but this will be fixed in my next commit.
public static object PrintMeow(object[] arguments)
{
foreach (var arg in arguments)
{
Console.Write((arg is null ? "null" : arg.ToString()) + " ");
}
return null;
}
...
var script = new Script();
script.SetGlobal("print", (MeowFunction)PrintMeow);
script.DoString("print(\"Hello world!\");"); // prints `Hello world!` to the console, do string returns what is returned from the script.To call a function for example lets say on unity update, you can do the following after you've initalized the script.
var update = script.GetGlobal("update");
if (update is Function func) // check if its a function
{
func.Call(script); // you need to reference the script in the call.
}