Reactive Programming 2.1 Functions and State

1. Stateful Objects A Stateful object

One normally describes the world as a set of objects, some of which has

State This changes over the course of time.

An object with a state if it behavior is influenced by it history.

An object is stateful if its behavior is influenced by history

EXAMPLE:A bank account had a state, because the answer to the question

"Can I withdraw CHF?"

May vary over the course of the lifetime of the

An account is stateful because of the question: Can I take 100 dollars? May not be the same answer at different times.

2. Objects with Var are not necessarily stateful

def Cons[t] (hd:t, tl: = = stream[t]) = new Stream[t] {def head = HD private var tlopt:option[stream[t]] = None def Tail:t = tlopt Match {case Some (x) + x Case None = + tlopt = Some (TL); tail}}

Each call to tail and head returns the same result.

3. Objects without var are not necessarily stateless

Class Bankaccountproxy (ba:bankaccount) {def deposit (amount:int): Unit = Ba.deposit (amount) def withdraw (Amount:int): Int = Ba.withdraw (amount)}

Reactive Programming 2.1 Functions and State