Rune

A beginner-friendly programming language built in Python.

Rune uses plain-English keywords and a clean, consistent grammar that can be learned in an afternoon. It is a dynamically typed, interpreted language with closures, first-class functions, and a small but complete standard library.

spell greet(name) {
    write("Hello, " + name + "!")
}

greet("world")

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Features

• Plain-English syntax — set, write, if / otherwise, while, repeat, count from/to
• Four data types — number, word, boolean (yes/no), empty
• First-class spells — functions as values, closures over their definition scope
• Loop control — skip (continue) and stop (break) in any loop
• Built-in functions — write, input, type, length, number, word
• Zero dependencies — pure Python 3.10+, nothing to install

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Quick Start

Prerequisites: Python 3.10 or later.

git clone https://github.com/kjxcodez/rune-lang.git
cd rune-lang

Run a file:

python -m rune.cli.main my_program.rune

Start the REPL:

python -m rune.cli.main

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Language at a Glance

Variables

set name = "Rune"
set score = 0
set active = yes

Conditionals

if score > 90 {
    write("A")
} otherwise score > 80 {
    write("B")
} otherwise {
    write("Try again")
}

Loops

# while loop
while count > 0 {
    write(count)
    set count = count - 1
}

# repeat a fixed number of times
repeat 5 times {
    write("again")
}

# count over a range
count from 1 to 10 as i {
    write(i)
}

Spells (Functions)

spell add(a, b) {
    return a + b
}

write(add(3, 7))   # 10

Closures

spell make_counter() {
    set n = 0
    spell increment() {
        set n = n + 1
        return n
    }
    return increment
}

set counter = make_counter()
write(counter())   # 1
write(counter())   # 2
write(counter())   # 3

Built-in Functions

Function	Description
write(…)	Print values to stdout
input(prompt)	Read a line from stdin
type(value)	Return the type name as a word
length(word)	Return the character count of a word
number(value)	Convert to number
word(value)	Convert to word (string representation)

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Project Structure

rune/
├── lexer/        # tokenises source text into tokens
├── ast/          # AST node definitions
├── parser/       # recursive-descent parser
├── runtime/      # tree-walk interpreter, environment, builtins
├── cli/          # command-line entry point and REPL
└── tests/        # integration test suite

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Running Tests

cd rune-lang
python -m unittest rune.tests.test_interpreter -v

24 tests, all passing.

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Documentation

Document	Description
Language Specification	Complete language reference
Architecture	How the interpreter is built
Glossary	Rune-specific terminology
Development Guide	Setup, workflow, adding features
Roadmap	Completed and planned features
Changelog	Version history
Contributing	How to contribute

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Roadmap

Completed: Lexer, Parser, AST, Interpreter, Closures, REPL, Architecture refactor.

Planned: Lists, Modules, Bytecode compiler, Virtual machine, LSP, Formatter, Package manager.

See docs/roadmap.md for the full list.

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Contributing

Contributions are welcome — bug reports, documentation, new features, or tooling. See docs/contributing.md to get started.

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License

MIT License — Copyright (c) 2025 Kapil Jangid. See LICENSE.