FinnLang 🐕

Dedicated to Finn (2018-2026) 🕊️

FinnLang is a simple, scripting language designed for learning interpreters and compiler basics. It supports basic variable declarations, expressions, control flow, and woofing. Also check out the gallery of dog pics.

Running the web sandbox locally 🐶

I made a web sandbox where you can play with FinnLang.

Here are the installation steps, enjoy!

Note: Make sure you have the latest versions of Cargo, and npm

1. Clone the Repository

git clone https://github.com/yourusername/finnlang.git
cd finnlang

1. Start the Backend Server Navigate to the backend directory and run the Rust server:

cd backend
cargo run --bin server

This'll start the FinnLang backend on localhost. Default is port 3000, but you can change it in server.rs.

1. Set Up and Run the Frontend In a new terminal window, go to the frontend sandbox directory:

cd ../finnlang-sandbox

Install the dependencies:

npm install

Then, start the development server:

npm run dev

This should open the web sandbox in your browser at http://localhost:5173 (or whatever Vite uses by default).

How to use in a CLI 🐶

1. Write your finnlang code in a .finn file, for example:

let x = 0;
while (x < 5) {
    woof(x);
    x = x + 1;
}

woof("Hello world");

Save this as file_name.finn in the ./backend folder.

1. Build and run the interpreter using Cargo:

cargo run -- file_name.finn

Replace file_name.finn with the path to your own .finn file if needed. (Or you can use your own file path)

1. Output will be printed to the terminal as your program executes.

Language Features 🐾

Types

• int — 64-bit signed integers
• bool — Boolean values: true or false
• string — Double-quoted strings "hello"
• double — Floating point numbers

Expressions

Supports:

• Arithmetic: + for numbers and string concatenation
• Boolean logic: && (and), || (or), ! (not)
• Comparison: ==, !=, < (less than)

let a = 5 + 3;
let b = "Hello, " + "world!";
let c = (a == 8);

Printing

Use woof to output values:

woof("Hello, world!");
let a = "HI";
woof(a);

If, Elif, Else Statements

Use if, elif, and else to declate conditionals. elif and else are entirely optional.

if (x < 0){
    woof("x is less than 0");
}elif (x == 5){
    woof("x is equal to 5");
}else{
    woof("x is something else");
}

For Loops

Repeat code with initialization, condition, and update:

for (let i = 0; i < 5; i = i + 1) {
    woof(i);
}

Functions

Define and call custom functions with the funct keyword:

// Function without parameters
funct sayHello() {
    woof("Hello, world!");
}

// Function with parameters
funct greet(name: string, age: int) {
    woof("Hello " + name + ", you are " + age + " years old!");
}

// Call functions
sayHello();
greet("Alice", 25);

Comments

Support for single-line and multi-line comments:

// This is a single-line comment

/* 
   This is a multi-line comment
   that can span multiple lines
*/

let x = 5; // End-of-line comment

While Loops

Repeat code while a condition is true:

let x = 0;
while (x < 5) {
    woof(x);
    x = x + 1;
}

Arrays

You can declare arrays of data

let nums = [0, 1, 2, 3, 4, 5];
let names = ["Alice", "Bob", "Charlie"];

Assignment

Assign new values to existing variables:

let count = 10;
woof(count);
count = count + 1;
woof(count);

Variable Declaration

Declare variables with let. (Type annotation is optional)

let x = 10;
let name: string = "Charlie";
let name2 = "Charlie";
let flag: bool = true;