===== L15. Introduction to Scala =====

<code scala>
/*
Sintaxa basic:
 */

val s = "Hello World"

def fibo(n: Int): Int =
  if (n == 0) 0
  else if (n == 1) 1
  else fibo(n-1) + fibo(n-2)

// varianta tail-recursiva
// cum putem defini functii auxiliare (where)
def fibo1(n: Int): Int = {

  def fib_aux(n: Int,
              last: Int,
              before_last: Int): Int =
    if (n == 0) last
    else fib_aux(n-1,before_last+last,last)

  fib_aux(n,1,0)
}

fibo(3)

/* Functii de ordin superior */

def sumOf(start: Int, stop: Int): Int = {
  def auxSum(crt: Int, acc: Int): Int =
    if (crt > stop) acc
    else auxSum(crt+1,acc+crt)

  auxSum(start,0)
}
/*
   Daca vrem sa calculam, in loc de
   x1 + x2 + ... + xn

   x1^2 + x2^ + ... xn^2

   f(x1) + f(x2) + ... + f(xn)

   Ce ar trebui sa facem ?
 */

def sumWithf (f: Int => Int,
              start: Int,
              stop: Int): Int = {
  def aux(crt: Int, acc: Int): Int =
    if (crt > stop) acc
    else aux(crt+1,acc+f(crt))
  aux(start,0)
}

def id (x: Int): Int = x
def square(x: Int): Int = x * x

sumWithf(x => x,0,10)
sumWithf(square,0,10)

/*
Cum definim functii anonime?
 */
(x: Int) => x // lambda x.x (peste intregi)
//x => x       // peste orice tip

(x: Int, y: Int) => x + y

/* un short-hard pt functii anonime */
val f: (Int,Int) => Int = _ + _

// nu putem scrie (x,y) => y + x folosind shorthand-ul anterior

val g: Int => Int = _ + 1

/* curry vs uncurry */

def uncurry(x: Int, y: Int, z: Int): Int = x + y + z

def curry(x: Int): Int => (Int => Int) = {
  def g(y: Int): Int => Int = {
    def h(z: Int): Int = x + y + z
    h
  }
  g
}

def curryNice(x: Int)(y: Int)(z: Int): Int = x + y + z

curry(1)(2)
val f: Int => Int = curryNice(1)(2)

def withf (f: Int => Int)(
              start: Int,
              stop: Int): Int = {
  def aux(crt: Int, acc: Int): Int =
    if (crt > stop) acc
    else aux(crt+1,acc+f(crt))
  aux(start,0)
}

//aduna valori dintr-un range
val fun : (Int,Int) => Int = withf(x => x)
val fun2 : (Int,Int) => Int = withf(x => x*x)
val fun3 : (Int,Int) => Int = withf(3*_)


</code>