beme-clj — begin/end and M-expressions for Clojure

M-expressions were McCarthy's original intended syntax for Lisp (1960). S-expressions were meant to be internal representation only — but they stuck. beme picks up where McCarthy left off: two rules that make nesting self-evident, while preserving Clojure's semantics exactly.

Rule 1 — head outside the parens: f(x y) => (f x y)

Rule 2 (optional) — begin/end instead of parens: f begin x y end => (f x y). You never need begin/end — everything can be written with Rule 1 alone. They exist for readability in multi-line blocks.

Escape hatch — '(...) and `(...) drop back to S-expression syntax inside: '(f (g x)) is (quote (f (g x))), not a call. When you need raw Clojure forms, just quote them.

begin and end are reserved words. If you need them as symbols, escape with slashes: /begin/ and /end/. The printer does this automatically for roundtrip fidelity.

Everything else is Clojure.

;; examples/stars.beme — bb beme run examples/stars.beme
require('[cheshire.core :as json])

defn begin stars [owner repo]
  let begin
    [
      url   str("https://api.github.com/repos/" owner "/" repo)
      resp  slurp(url)
      data  json/parse-string(resp true)
      count :stargazers_count(data)
    ]

    println(str(owner "/" repo ": " count " ⭐"))
  end
end

stars("beme-lang" "beme-clj")

Installation

Add to deps.edn:

io.github.beme-lang/beme-clj {:mvn/version "0.5.0-alpha"}

Or clone and use directly:

git clone https://github.com/beme-lang/beme-clj.git
cd beme-clj

All namespaces live under beme.alpha to signal that the API is pre-1.0 and may change. When the API stabilizes, namespaces will move to beme.

Getting Started

Run a .beme file:

$ bb beme run hello.beme                                # Babashka
$ clojure -T:beme run :file '"hello.beme"'              # Clojure JVM
Hello, world!

Interactive REPL:

$ bb beme repl                                          # Babashka
user=> +(1 2)
3
user=> map(inc [1 2 3])
(2 3 4)

Convert between beme and Clojure (direction detected from extension):

$ bb beme convert hello.beme                            # .beme → Clojure
$ bb beme convert hello.clj                             # .clj → beme
$ clojure -T:beme convert :file '"hello.beme"'          # Clojure JVM

Format .beme files (normalize syntax via pprint):

$ bb beme format hello.beme                             # in-place
$ bb beme format src/                                   # directory, recursive

Requires Babashka or Clojure.

Editor Support

Editor	Repository	Features
Zed	zed-beme	Syntax highlighting, brackets, indentation, symbol outline
VS Code	vscode-beme	Syntax highlighting, brackets, indentation, folding

Tree-sitter grammar: tree-sitter-beme

Documentation

• Language Reference — complete syntax guide
• API Reference — public functions
• Development — testing, architecture
• Design Decisions — rationale behind each choice
• Product Requirements — requirements and known limitations