reader.md

Reader

The Reader monad represents a computation, which can read values from a shared environment, pass values from function to function, and execute sub-computations in a modified environment. It is also usefull when it comes to dependency injections

Implements: Monad

• Reader
  • Reader(f)
  • .of
  • .toString()
  • .map(f)
  • .getValue()
  • .ap(t)
  • .chain(f)
  • .runWith(e)

Reader(f)

Reader constructor

Param	Type	Description
f	function	A function of the form (e -> a) that is wrapped by the Reader, nothing is executed until it is run with an environment

Reader.of(v)

Reader constructor that populates the right portion with it's argument. of essentially will lift a value of type a into a Reader

Param	Type	Description
v	any	any value that needs to be lifted to the Reader

Reader.toString()

Get a stringified version of the Reader

Reader.map(f)

Apply the function f to the right portion of the Reader

Param	Type	Description
f	function	Function

Reader.getValue()

Get the function within the Reader

Reader.ap(t)

ap allows for values wrapped in a Reader to be applied to functions also wrapped in a Reader. In order to use ap, the Reader must contain a function as its value.

Param	Type	Description
t	Reader	Reader with function as the second element

Reader.chain(f)

Chain together many computations that return a Reader

Param	Type	Description
f	function	Function that returns another Reader

Reader.runWith(e)

As Reader is a lazy datatype that requires a shared environment to run, it's instance provides a runWith method that takes in an environment and returns the result of the computation.

Param	Type	Description
e	any	An environment that needs to be passed to the Reader