Functional programming

Functional programming

• 1.
  Functional Programming
• 2.
  Idea • Restrictedsense, a functional programming language is one which does not have mutable variables, assignments, or imperative control structures. • Wider sense, a functional programming language enables the construction of elegant programs that focus on functions. So it will be easier to be distributed
• 3.
  High-order funtion •Function – as paramters – as result => Currying : f(x,y) => z = g(x)(y) => z
• 4.
  Quiz //greatest commondivisor of two numbers def gcd(a:Int, b:Int): Int = if (b==0) a else gcd(b, a%b) //factorial number def factorial(n:Int): Int = if (n==0) 1 else n*factorial(n-1) What is different between recursion call of gcd and factorial
• 5.
  Tail recursion •“If a function calls itself as its last action, the function’s stack frame can be reused” => Never be stackoverflow again with recursion • All recursion can be rewrite to tail recursion
• 6.
  Exercise 1 •Rewrite factorial as tail-recursion
• 7.
  Think about loopin different way • Basically for loop = f(c) with c is a collection
• 8.
  Think about loopin different way (2) Does a string have an uppercase character Java Scala
• 9.
  Think about loopin different way (3) Return all even member of a collection and time 2 Java : Cannot fit this slide (shame on you, java) Scala val rs = input.filter(_%2==0).map(_*2)
• 10.
  Think about loopin different way (4) • exists • filter • find • forall • foreach • map • reduce