Option/Maybe Monad in CoffeeScript

gistfile1.coffee

# Implementation defines behaviour instead of state.

None = 
  map: (func) -> None
  flatMap: (func) -> None
  forEach: (func) -> # Nothing!
  getOrElse: (def) -> def
  isDefined: () -> false
  fold: (empty, notEmpty) -> empty()
  
Some = (val) ->
  map: (func) -> Some(func(val))
  flatMap: (func) -> func(val)
  forEach: (func) -> func(val)
  getOrElse: (def) -> val
  isDefined: () -> true
  fold:(empty, notEmpty) -> notEmpty(val)
  
Option = (val) ->
  if val == undefined || val == null
    None
  else
    Some(val)

# then you can...
maybe = Option(null)

maybe.forEach (val) ->
  console.log(val)
	
maybe2 = Option(2)

maybe3 = maybe2.flatMap (val) ->
  if val == 2
    None
  else 
    Some(val)
		
maybe3.fold(
  () -> 
    console.log("nothing!")  
  (val) -> 
    console.log("Something " + val)
)

# > nothing!