Future that can have a value applied to its map function

app-submit-example.js

// submit :: event -> IO[ HttpGet[ Either [ HttpPost []]]]
const submit = (event) => {
  return getFormFields()
  .map(incrementVersionNumber)
  .map(saveRecord)
}

// getFormFields :: () -> IO
const getFormFields = () => IO(()=>{
  return lift()
})

const split = SingleChar( 
                c => AnyString(
                        s => s.split(c) 
                      ) 
                )

future-example.js

const f = Future((reject,resolve)=> setTimeout(m=>resolve("hello"),1000))
.map(x=>x+' world')
.map(s=>s.toUpperCase())
f.fork(console.error, console.log)

future.js

const Future = function(){}
Future.of = (forkr, mapr=x=>x) => { 
  return Object.assign(new Future(), {
    map:  (f)=> Future(forkr, x=>f(mapr(x))),
    fork: (err,success)=> { 
      forkr(err,x=>success(mapr(x))) 
    },
    apply: x => mapr(x)
  })
}
Future.subType = function(makeForkr,argNames){
  function ctor(...args){
    const objProps = argNames.reduce((obj,k,i)=>{obj[k]= args[i]; return obj},{})
    return Object.assign(Object.create(ctor.prototype), objProps, Future.of(makeForkr(...args)))
  }
  ctor.prototype = Future.prototype
  return ctor
}

httpget.js

const HttpGet = function(){}
HttpGet.of = (url,headers={accept:'application/json'}) => {
  return Object.assign(
      new HttpGet()
    , {url,headers}
    , Future((rej,res)=>{ request({url,headers},(err,succ)=>err? rej(err) : res(succ) )})
  )
}