LyangLang

A toy programming language with Romanized Nepali keywords, written in Rust. Source files use .nbh. Run with lyangpiler.

Two execution backends: tree-walking interpreter (default) and a bytecode VM (--vm). Both produce identical results.

Install

Quickest (no Rust needed):

# macOS / Linux
curl -fsSL https://raw.githubusercontent.com/Konseptt/LyangLang/main/install.sh | bash

# Windows (PowerShell)
irm https://raw.githubusercontent.com/Konseptt/LyangLang/main/install.ps1 | iex

From crates.io (needs Rust):

cargo install lyanglyang --locked

Build from source:

git clone https://github.com/Konseptt/LyangLang.git
cd LyangLang
cargo build --release
./target/release/lyangpiler run example.nbh

Direct download: grab the binary for your OS from Releases.

System	Download
Windows 64-bit	lyangpiler-windows-x86_64.zip
Linux 64-bit Intel/AMD	lyangpiler-linux-x86_64.tar.gz
Linux 64-bit ARM	lyangpiler-linux-aarch64.tar.gz
macOS Apple Silicon	lyangpiler-macos-aarch64.tar.gz
macOS Intel	lyangpiler-macos-x86_64.tar.gz

Run a program

lyangpiler run file.nbh           # tree-walking interpreter (default)
lyangpiler run file.nbh --vm      # bytecode VM backend

Legacy shorthand: lyangpiler file.nbh --vm works the same.

lyangpiler check file.nbh         # validate syntax, don't execute
lyangpiler new myproject          # scaffold a new project

After install, Mac/Linux users may need source ~/.lyangpiler/enable.sh or a fresh terminal for lyangpiler to appear on PATH.

Language reference

Keywords are Romanized Nepali. Every word in a two-word keyword (like bol mug, oi mug) must be typed as-is.

Print

bol mug "Namaste, world!"              // print literal string
bol mug "Namaste " + naam + "!"         // string concatenation with +
bol mug "Number: " + age                // variable in string (autoconverted)

Variables

oi mug age = 25                         // declare number variable
oi mug naam = "Ram"                     // declare string variable

Input

oi mug bhan naam                        // prompt "> ", read input into naam

bhan reads a string from the user. To use input in arithmetic you'd need to convert it, but LyangLang doesn't have a parse/convert function yet. So bhan is for strings, and oi mug x = 5 is for numbers.

Arithmetic

All use checked arithmetic, so overflow crashes instead of wrapping silently.

mug jod a, b lai sum                    // sum = a + b
mug ghata a, b lai diff                 // diff = a - b
mug guna a, b lai prod                  // prod = a * b
mug bhag a, b lai quot                  // quot = a / b (division by zero crashes)

Conditionals

// if-then-end
yedi age babaal "18" bhane
    bol mug "Adult"
sakiyo

// if-else if-end
yedi rang babaal "rato" bhane
    bol mug "Red"
aile feri rang babaal "nilo" bhane
    bol mug "Blue"
sakiyo

• yedi / yadi: if (both work, same token)
• babaal: equals comparison
• laamo: not-equals comparison
• bhane: then
• aile feri: else-if
• sakiyo: end of block

String comparisons are case-insensitive in both backends ("RATO" babaal "rato" is true).

Comments

// This is a comment, everything after // is ignored

Keyword quick reference

Syntax	Meaning	Nepali word
bol mug	print	bol = speak, mug = emphasis
oi mug	declare variable	oi = exclamation, mug = emphasis
oi mug bhan	read input	bhan = speak/say
mug jod	add	jod = join/add
mug ghata	subtract	ghata = decrease
mug guna	multiply	guna = multiply
mug bhag	divide	bhag = share/divide
lai	into (target of operation)	lai = to (dative)
yedi / yadi	if	yedi/yadi = if
babaal	equals condition	(slang, repurposed)
laamo	not-equals condition	laamo = long (repurposed)
bhane	then	bhane = then
aile feri	else-if	aile = now, feri = again
sakiyo	end block	sakiyo = finished/done

Examples

Hello World

bol mug "Namaste, world!"

Greet the user

bol mug "Timro naam k ho?"
oi mug bhan naam
bol mug "Namaste, " + naam + "!"

Calculator

oi mug a = 12
oi mug b = 4

mug jod a, b lai sum
bol mug "Jod (add): " + sum
mug ghata a, b lai diff
bol mug "Ghata (subtract): " + diff
mug guna a, b lai prod
bol mug "Guna (multiply): " + prod
mug bhag a, b lai quot
bol mug "Bhag (divide): " + quot

Color picker (conditionals)

bol mug "Timro man pasand rang?"
oi mug bhan rang

yedi rang babaal "rato" bhane
    bol mug "Rato rang, energy high!"
aile feri rang babaal "nilo" bhane
    bol mug "Nilo rang, chill vibes."
aile feri rang babaal "hariyo" bhane
    bol mug "Hariyo rang, nature mode."
sakiyo

Full demos in repo

lyangpiler run example.nbh              # variables, arithmetic, I/O, conditions
lyangpiler run myapp/main.nbh           # shop calculator, slang, multi-branch

Error handling

Four error types, reported to stderr with line info:

• LexError: malformed tokens or unterminated strings
• ParseError: grammar violations (missing bhane, sakiyo, etc.)
• RuntimeError: overflow, division by zero
• NameError: undefined variable
• TypeError: wrong type in arithmetic or comparison

Project structure

src/
  lexer.rs          source → tokens
  parser.rs         tokens → AST
  ast.rs            Statement / expression types
  token.rs          Token enum
  interpreter.rs    tree-walking backend (default)
  compiler.rs       AST → bytecode
  bytecode.rs       Opcode / Value definitions
  vm.rs             bytecode VM backend
  error.rs          error types + formatting
  main.rs           CLI (clap)
example.nbh         feature tour
myapp/main.nbh      longer interactive demo

Development

cargo build                               # build
cargo test                                # run tests (lexer, parser, vm, interpreter)
cargo test -- --nocapture                 # verbose output
cargo clippy                              # lints
cargo run -- run example.nbh --vm         # quick try

Contributing

1. Fork the repo
2. Create a branch: git checkout -b feature-name
3. Make changes, add tests alongside
4. cargo build && cargo test must stay green
5. Push and open a pull request

Troubleshooting

Command not found after install?

• Mac/Linux: source ~/.lyangpiler/enable.sh or open a new terminal
• Windows: confirm %USERPROFILE%\.lyangpiler\bin is on your PATH

Build failures?

• rustup update stable then cargo clean && cargo build

Runtime errors?

• Check for missing sakiyo to close blocks
• String comparisons: use yedi var babaal "value" not yadi var == "value"
• Arithmetic operands must be declared numbers

License

MIT