a_sparkfun-inventor-guide-circuit-04-multiple-leds-with-johnny-five-and-nodejs.js

var five = require('johnny-five'),
    foldl = require('./hof').foldl

var leds =
  [ 2
  , 3
  , 4
  , 5
  , 6
  , 7
  , 8
  , 9
  ]

board = new five.Board()

board.on('ready', function() {
  console.log('(-)(+)')

  function runInteraction (interaction) {
    return function runInteractionInLED(z, led, next) {
      process.stdout.write(interaction === 'fadeIn' ? '+' : '—')
      console.log(led)
      led = new five.Led(led)
      led[interaction]()
      setTimeout(function () {
        next()
      }, 300)
    }
  }

  function runAllInteractions(z, interaction, next) {
    var l = JSON.parse(JSON.stringify(leds)) //clone
      , f = runInteraction(interaction)

    foldl(f, null, l, next)
  }

  foldl(runAllInteractions, null, ['fadeIn', 'fadeOut'], function done() {
    console.log('(+)(-)')
    process.exit()
  })
})

hof.js

var p = require('p'),
  map = p(),
  mapa = p(),
  zip_with = p(),
  filtera = p(),
  maybe = p(),
  foldl = p(),
  _, f, ac, l, l1, l2, cb, errcb, z;

// error handling for conditional execution of functions
maybe(Error, _, errcb, cb, function(err, data, errcb, cb) {
  errcb(err);
});
maybe(_, _, errcb, cb, function(err, data, errcb, cb) {
  cb(data);
});

// map
// map _ []     = []
// map f (x:xs) = f x : map f xs
map(_, [], ac, cb, function map_done(f, l, ac, cb) {
  return cb(ac);
});
map(f, l, ac, cb, function map_catch_all(f, l, ac, cb) {
  ac.push(f(l.shift())); // head
  map(f, l, ac, cb); // l is now tail
});

// map with async f, no error possible
mapa(f, [], ac, cb, function map_done(f, l, ac, cb) {
  return cb(ac);
});
mapa(f, l, ac, cb, function map_catch_all(f, l, ac, cb) {
  f(l.shift(), function(x) {
    ac.push(x);
    mapa(f, l, ac, cb); // l is now tail
  });
});

// filter with async f
// filter _ [] = []  
// filter p (x:xs)   
//     | p x       = x : filter p xs  
//     | otherwise = filter p xs
filtera(_, [], ac, cb, function filter_done(f, l, ac, cb) {
  return cb(null, ac);
});
filtera(f, l, ac, cb, function filter_catch_all(f, l, ac, cb) {
  var head = l.shift();
  f(head, function(err, ok) {
    maybe(err, ok, cb, function(ok) {
      if (ok) ac.push(head);
      filtera(f, l, ac, cb); // l is now tail
    });
  });
});

// foldl with async f, no errors possible
// foldl f z []     = z                  
// foldl f z (x:xs) = foldl f (f z x) xs
foldl(f, z, [], cb, function foldl_done(f, z, l, cb) {
  cb(z);
});
foldl(f, z, l, cb, function foldl_all(f, z, l, cb) {
  f(z, l.shift(), function foldl_f_async(new_z) {
    foldl(f, new_z, l, cb);
  });
});

// zipWith _ [] _ = []  
// zipWith _ _ [] = []  
// zipWith f (x:xs) (y:ys) = f x y : zipWith' f xs ys
zip_with(_, [], _, ac, cb, function emptyl1(f, l1, l2, ac, cb) {
  cb(ac);
});
zip_with(_, _, [], ac, cb, function emptyl2(f, l1, l2, ac, cb) {
  cb(ac);
});
zip_with(f, l1, l2, ac, cb, function all(f, l1, l2, ac, cb) {
  ac.push(f(l1.shift(), l2.shift()));
  zip_with(f, l1, l2, ac, cb);
});

module.exports = {
  map: map,
  map_async: mapa,
  zip_with: zip_with,
  filter_async: filtera,
  foldl: foldl
};