Generators let you cut away at boiler-plate. Here I'm using it to do similar things to Haskell's Maybe, which effectively defines an error state (e.g NaN) once, and then write a lot of code that doesn't now have to bother checking for it explicitly. The numericalProcess can now be defined without any checking for NaN, in a point-free (not refere…

maybe-es6.js

var Nothing = {Nothing: true}

function MaybeGenerator() {
  var g = arguments[arguments.length - 1]
  // list of functions that test for any "Nothing" values
  var maybes = [].slice.call(arguments,0,arguments.length - 1)

  return function(value) {
    var generator = g.apply(null,[].slice.call(arguments,1))
    var result
    var nothing = false
    while(result = generator.next(), !result.done) {
      value = result.value.call(null,value)
      if(maybes.some(function(mf) { return mf(value) })) {
        return Nothing
      }
    }
    return value
  }
}


var numericalProcess = function*() {
  yield Math.log
  yield function(x) { return x - 1 }
  yield Math.log
  yield Math.sqrt
  yield Math.log
}


var safeNumericalExample = MaybeGenerator(isNaN,numericalProcess)

var shouldBeNothing = safeNumericalExample(-1)
var becomesNothingLater = safeNumericalExample(1)
var someNormalNumber = safeNumericalExample(1205)

console.log(shouldBeNothing)   // Nothing
console.log(becomesNothingLater)   // Nothing
console.log(someNormalNumber) // 0.29592896553598536...