CafeScripto

CoffeeScript-syntax AffineScript. Significant whitespace, arrow functions, postfix conditionals, @ shorthand — and behind the surface, affine resource guarantees and typed-wasm output.

Table of Contents

• What it is
• Hello
• Install
• Use
• Different faces, same cube
• Why CafeScripto
• Limitations (deferred)
• Status
• License

What it is

CafeScripto is AffineScript with its cafe face pre-selected. CoffeeScript developers will recognise: (args) → body arrows, @x for self, unless and until, postfix if / unless, Yes/No/On/Off literal aliases, line comments, ## block comments, and significant indentation.

This repo is a brand surface only. The compiler lives in affinescript. This repo carries:

• Examples idiomatic to CoffeeScript developers

• A cafe shim CLI that aliases affinescript --face cafe

• Migration guides for CoffeeScript codebases (most have already migrated to JS / TS, but the syntax is still beloved by some)

Hello

examples/hello.affine:

# face: cafescripto

###
  Distinctive features exercised below:
    - `#` line comments and `###` block comments
    - paren-arrow `(args) -> body`
    - bare-arrow `-> body`
    - Yes/No/On/Off literal aliases
###

effect IO {
  fn println(s: String) -> ();
}

fn main() -{IO}-> () {
  let greeting = "Hello, CafeScripto!";
  let ready = Yes;
  println(greeting);
}

Install

opam install affinescript
git clone https://github.com/hyperpolymath/cafescripto
cd cafescripto

Use

# Direct, via affinescript:
affinescript eval --face cafe examples/hello.affine
affinescript compile --face cafe examples/hello.affine -o hello.wasm

# Or via the cafe shim:
./bin/cafe eval examples/hello.affine

# Or via the justfile:
just run examples/hello.affine
just preview examples/hello.affine    # show the canonical lowering

Source files use the canonical .affine extension. The face is selected by the # face: cafescripto pragma on the first comment line, or by the --face cafe flag.

Different faces, same cube

CafeScripto is one of six established faces over the AffineScript core:

• AffineScript — the canonical face

• RattleScript — Python-style

• JaffaScript — JavaScript / TypeScript-style

• LucidScript — PureScript / Haskell-style

• CafeScripto — CoffeeScript-style (this repo)

• PseudoScript — pseudocode-style

Why CafeScripto

CoffeeScript peaked in 2014 and most of its population migrated to TypeScript or vanilla JavaScript years ago. CafeScripto isn’t a mass-market acquisition play; it’s a category-builder, and a comfortable destination for developers who liked CoffeeScript’s syntax aesthetics and want it back, but with stronger guarantees and a real runtime story (typed-wasm everywhere).

Limitations (deferred)

Some CoffeeScript surface features need AST-level rewrites that the text-to-text face transformer doesn’t yet handle:

• List comprehensions ((x*2 for x in xs when x>0))

• No-paren calls (f x, y)

• Splat / destructuring (…​args)

• String interpolation ("Hello, #{name}")

These are tracked in the affinescript faces README. Until they land, write the explicit forms (.map / .filter, paren-everything calls, explicit string concat).

Status

Alpha. The face transformer is implemented in affinescript/lib/cafe_face.ml (added in commit 74024c6).

License

AGPL-3.0-or-later. See LICENSE.