ember

A small dynamically typed language with its own bytecode VM. C++20, no runtime deps.

WIP. Build window: Jul–Aug 2026. See docs/build-plan.md.

Pipeline

lexer → pratt parser → bytecode compiler → stack VM → mark-sweep GC

Example

fn fib(n) {
    if n < 2 { return n }
    return fib(n - 1) + fib(n - 2)
}

fn make_counter() {
    let count = 0
    return fn() {
        count = count + 1
        return count
    }
}

let c = make_counter()
print(c())      // 1
print(c())      // 2
print(fib(30))  // 832040

Features (v1)

• Types: Number (f64), Bool, String, Nil, Function, Closure
• First-class functions, closures with upvalue capture
• if/else, while, return
• Arithmetic, comparison, logical ops
• String interning
• Built-ins: print, clock, type, len
• Tri-color mark-sweep GC with write barriers

Targets

what	target
fib(30)	< 50 ms
vs tree-walker	≥ 3×
GC p99 pause (1M objects)	< 2 ms
diff-fuzz cases	100K+ passing
CI	clean under ASan + UBSan

Build

cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build
./build/ember run examples/fib.em
./build/ember dis examples/fib.em
./build/ember repl
./build/ember_bench

Docs

• docs/language.md
• docs/isa.md
• docs/gc.md
• docs/build-plan.md

References

• Nystrom, Crafting Interpreters (clox, ch. 14–30)
• Pratt, "Top Down Operator Precedence" (1973)
• Wilson, "Uniprocessor Garbage Collection Techniques" (1992)

License

MIT