Lumen

Lumen is a small, embeddable scripting language. Source files (.lmn) are compiled to compact bytecode (.bin) that a tiny stack-based virtual machine executes. The same VM runs on the desktop, in the browser (WebAssembly), on microcontrollers and inside host applications.

println('Hello, world!')

print('What`s your name? ')
name = inputStr()

greeting = 'Hello, ' .. name .. '!'
println(greeting)

What the language looks like

• Line-oriented. One statement per line, no semicolons, block statements closed with endif, endwhile, endrepeat, endroutine, endfunction.
• Dynamically typed. Values are integers, floats or strings, and a variable can change type on every assignment. No declarations.
• Function-call syntax. Built-ins, routines and functions are called with parentheses: println('x'), n = str2int('42').
• Global state. All variables are global; routines and functions share them.
• Arrays. Named, growable, untyped arrays: scores[0] = 10.
• Modular. import 'file.lmn' pulls another script into the program.
• Garbage-collected memory. Variable and array storage lives in a managed heap with a mark-and-sweep collector.

How this book is organised

• Getting Started covers building the interpreter, writing a first program and the command line.
• Language Guide documents every statement and operator.
• Examples are complete programs you can generate with lumen --examples <name>.
• Architecture, Debugging & Tooling and Reference describe the compiler, the bytecode, the VM, the debugger and every opcode and built-in function.
• Lumen in apps and Platforms & Ports describe projects that embed or port the VM. They follow their own release schedule and may lag behind the language described in the Language Guide.

This book describes Lumen v4 (lumen --version).