// function* bears () {

// var kind = yield 'grizzly'

// yield kind + ' polar'

// console.log('kind: ' + kind)

// return 'done'

// }

// var bear = bears()

// console.log(bear.next().value)

// console.log(bear.next('ferocious').value)

// console.log(bear.next().value)

var fs = require('fs')

run(function* (resume) {

var contents = yield fs.readFile('big.file', 'utf8', resume)

var uppercase = contents.toUpperCase()

yield fs.writeFile('uppercase.file', uppercase, resume)

console.log('All done!')

})

function run (generator) {

var data = null, yielded = false

var iterator = generator(function () {

data = arguments

check()

})

yielded = !!(iterator.next())

check()

function check () {

while (data && yielded) {

var err = data[0], item = data[1]

data = null

yielded = false

if (err) return iterator.throw(err)

yielded = !!(iterator.next(item))

}

}

}