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Wren is a small, fast, class-based concurrent scripting language

Think Smalltalk in a Lua-sized package with a dash of Erlang and wrapped up in a familiar, modern syntax.

System.print("Hello, world!")

class Wren {
  flyTo(city) {
    System.print("Flying to %(city)")

var adjectives = Fiber.new {
  ["small", "clean", "fast"].each {|word| Fiber.yield(word) }

while (!adjectives.isDone) System.print(adjectives.call())
  • Wren is small. The VM implementation is under 4,000 semicolons. You can skim the whole thing in an afternoon. It's small, but not dense. It is readable and lovingly-commented.

  • Wren is fast. A fast single-pass compiler to tight bytecode, and a compact object representation help Wren compete with other dynamic languages.

  • Wren is class-based. There are lots of scripting languages out there, but many have unusual or non-existent object models. Wren places classes front and center.

  • Wren is concurrent. Lightweight fibers are core to the execution model and let you organize your program into an army of communicating coroutines.

  • Wren is a scripting language. Wren is intended for embedding in applications. It has no dependencies, a small standard library, and an easy-to-use C API. It compiles cleanly as C99, C++98 or anything later.

If you like the sound of this, let's get started. You can even try it in your browser! Excited? Well, come on and get involved!

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