Lahlang 🇸🇬

A programming language for Singaporeans, by not a Singaporean yet. Can one lah!

Table of Contents

• Overview
• Documentation
• Features
• Installation
• Usage
• Language Examples
• Wall of Lah
• CLI Options
• Project Structure
• Architecture
• Testing
• Contributing
• Support
• Star History
• License

Overview

Lahlang is a fun, expressive programming language inspired by Singlish and Singaporean culture. It’s designed for learning, experimentation, and joy, with syntax and keywords that reflect local slang and humor.

Documentation

For a complete guide on how to use Lahlang, check out our extensive documentation:

1. Installation Guide: Node.js/pnpm prerequisites and global CLI installation.
2. VS Code Extension: How to get syntax highlighting.
3. Getting Started: Your first .lah file and "Hello World".
4. Variables and Types: Data handling with Singlish types.
5. Control Flow: Logic with confirm or not and which one lah.
6. Loops: Iteration with keep going lah and every one also.
7. Functions: Defining and calling reusable blocks.
8. Error Handling: Wholesome and Spicy 🌶️ tiers.
9. CLI Reference: Commands, debugging, and meta keywords.
10. Examples Walkthrough: Deep dive into the examples/ folder.

Features

• Singlish Syntax: Keywords like eh listen lah, ok lah bye, oi, confirm or not, keep going lah, etc.
• Interactive REPL: Run lahlang with no arguments to enter the REPL — type Singlish code line by line with multi-line support.
• VS Code Support: Get syntax highlighting with the Lahlang VS Code Extension.
• Variables & Constants: eh got, confirm got
• Control Flow: confirm or not (if), or maybe (else if), abuden (else), keep going lah (while), one by one lah (for), every one also (foreach), hantam lah...until (do-while)
• Functions: steady lah do this, here take, eh do this, one time only, jio (casual call)
• Error Handling: see how lah, aiyoh kena, confirm do, jialat throw, paiseh warn, hong gan lah, chao cb assert, act blur (silent try)
• Types: words (string), nombor (number), can cannot (boolean), whole list (array), all the things (object)
• Singlish Expressions: kaypoh (typeof), gostan (reverse), swee (pretty print), agak agak (round), makan (pop), tabao (clone), chope (freeze), sabo (delete), die die must (assert), sian/lepak (sleep)
• Built-in Methods: String methods (.upper(), .lower(), .trim(), .split(), etc.), array methods (.push(), .pop(), .map(), .filter(), etc.), object methods (.keys(), .values(), .entries()), and global helpers (panjang, to_nombor, to_words, math functions)
• String Escapes: \n, \t, \r, \\, \" inside double-quoted strings
• Operators: same same (==), not same (!=), and also (&&), or can (||), add some more (+=), minus a bit (-=)
• Comments: // shiok: (single-line), wahlau start ... wahlau end (multi-line)
• Meta: chiong bring in (import), share out (export), eh check this (debug/inspect)
• Spicy Error Types: JialatError, BoJioError, SiaoError, TokKokError, TanKuKuError, SuayError, WahLauError, GoneCase, CbError, LanJiaoError, CcbError

Installation

Install globally using pnpm:

pnpm i -g lahlang

Usage

Run a .lah file:

lahlang myfile.lah

Or start the interactive REPL:

lahlang

lah> oi "Hello from REPL!"
Hello from REPL!
lah> eh got x = 42
lah> oi x + 8
50

Type Singlish code directly — no need for eh listen lah / ok lah bye wrappers. Multi-line blocks (with {}) are supported. Press Ctrl+C to exit.

To close REPL with a keyword, type bye lah on its own line.

Language Examples

Hello World

eh listen lah
	oi "Hello World";
ok lah bye

FizzBuzz

eh listen lah
	one by one lah (i from 1 to 15) {
		confirm or not (i % 15 same same 0) {
			oi "FizzBuzz";
		} or maybe (i % 3 same same 0) {
			oi "Fizz";
		} or maybe (i % 5 same same 0) {
			oi "Buzz";
		} abuden {
			oi i;
		}
	}
ok lah bye

Data Structures

eh listen lah
	eh got my_list = [1, 2, "shiok", can];
	oi my_list;
	every one also (item in my_list) {
		oi item;
	}
	eh got my_bag = {
		food: "Chicken Rice",
		price: 4.5,
		tasty: can
	};
	oi my_bag;
ok lah bye

Advanced Logic

eh listen lah
	steady lah do this makeCounter(start) {
		eh got count = start;
		steady lah do this increment() {
			eh change count = count + 1;
			here take count;
		}
		here take increment;
	}
	eh got my_counter = makeCounter(10);
	oi my_counter();
ok lah bye

Singlish Expressions

eh listen lah
	// typeof
	oi kaypoh "hello";          // "words"
	oi kaypoh 42;               // "nombor"

	// reverse
	oi gostan "lahlang";        // "gnalhal"
	oi gostan [1, 2, 3];        // [3, 2, 1]

	// round
	oi agak agak 3.7;           // 4

	// pretty print
	eh got obj = { name: "Ah Beng", age: 25 };
	swee obj;

	// clone and freeze
	eh got copy = tabao obj;
	chope obj;

	// silent error handling
	act blur {
		jialat throw "this error is swallowed";
	}

	// assert
	die die must (1 + 1 same same 2);
ok lah bye

Do-While Loop

eh listen lah
	eh got i = 0;
	hantam lah {
		oi i;
		eh change i = i + 1;
	} until (i less than 5)
ok lah bye

Built-in Methods

eh listen lah
	// String methods
	eh got s = "hello world";
	oi s.upper();               // "HELLO WORLD"
	oi s.split(" ");            // ["hello", "world"]
	oi panjang(s);              // 11

	// Array methods
	eh got arr = [3, 1, 2];
	oi arr.sort();              // [1, 2, 3]
	oi arr.map(steady lah do this(x) { here take x * 2; });

	// Type conversion
	oi to_nombor("42");         // 42
	oi to_words(100);           // "100"
ok lah bye

Wall of Lah

We do it for the community one lah.

Contribute any .lah example and get featured automatically as a repository contributor on the Wall of Lah.

See contribution details in wall-of-lah/README.md.

CLI Options

• lahlang <file.lah>: Run a Lahlang program.
• lahlang: Start the interactive REPL.
• Only .lah files are accepted.
• Errors are reported in Singlish style, e.g. [TOK KOK], [RUNTIME ERROR], [FATAL], [ALAMAK].

Project Structure

lahlang/
├── src/                # Source code (lexer, parser, interpreter, CLI)
├── examples/           # Example .lah programs
├── tests/              # Unit and integration tests
├── package.json        # Project metadata and scripts
├── tsconfig.json       # TypeScript config
├── vitest.config.ts    # Test config

Architecture

• Lexer: Tokenizes source code using Singlish keywords.
• Parser: Builds AST from tokens, supports all language features.
• Interpreter: Executes AST, manages environment, handles errors.
• CLI: Entry point for running .lah files, handles file I/O and error reporting.

Testing

Run all tests with:

pnpm test

• Uses Vitest for unit and integration tests.
• Test coverage includes lexer, parser, interpreter, error handling, and full language features.

Contributing

Contributions are welcome! Please open issues or pull requests for:

• Bug fixes
• Feature requests
• Documentation improvements
• New examples

Star History

Support

If Lahlang helps you or made you smile, you can support the project here:

• GitHub Sponsors: https://github.com/sponsors/suryanshkushwaha
• Buy Me a Coffee: https://buymeacoffee.com/suryanshkushwaha

License

MIT License