callcc with javascript generators

abort.js

function*example() {
    const x = 10
    const y = yield callcc(function*(k) {
        // ...
        yield k(20)
        throw "Unreachable code"
    })
    console.log(x + y)
}

stepGen(example())

callcc.js

function stepGen(gen, k = ()=>{}, arg) {
    const {value, done} = gen.next(arg)
    if(done) {
        return k(value)
    }
    else if(typeof value.next === 'function') {
        return stepGen(value, v => stepGen(gen, k, v))
    }
    else {
        return value(x => stepGen(gen, k, x))
    }    
}

function callcc(gf) {
    return k => {
        const gen = gf(result => _ => k(result))
        stepGen(gen, k)
    }
}

coroutines.js

let threads = []

function* exit() {
    if(threads.length > 0) {
        const nextK = threads.shift()
        yield nextK()
    }
}

function fork(fn, ...args) {
    threads.push(() => k => stepGen(fn(...args), k))
    return k => k()
}

const next = callcc(function*(k) {
    threads.push(k)
    const nextK = threads.shift()
    yield nextK()
})

function* proc(id, n) {
    for(let i = 0; i <= n; i++) {
        console.log(`proc ${id}:`, i)
        yield next
    }
    yield exit()
}


function* main() {
    console.log('start main')
    yield fork(proc, 1, 4)
    yield fork(proc, 2, 4)
    yield fork(proc, 3, 4)
    yield next
    console.log('end main')
    yield exit()
}