Scala Functions

Function : A function is computational unit in a program.

Function :
  • To define a function specify - name, parameter, body and return type.  
  • Functions are implicitly declared as abstract if leave off the equal sign and method body.
  • Remove = sign if not to return any thing.
  • A function can have named and optional parameters.
  • Use Unit if the function does not return anything. (Unit is equivalent to Void in java)
Function definition : def functionName ([list of parameters]) : [return type]
     
      Abstract Function : Ex - def calculation (a:Int, b:String)
      Non Abstract Function :  def functionName ([list of parameters]) : [return type] = { }
      
      Example -
  
   def calculation(a: Int, b: Int): Int = {
    var sum: Int = 0
    sum = a + b
    return sum
   }

Function Recursion:
  • Head Recursion
  • Tail Recursion
Head Recursion:
  • It stores result values in stack which may cause stack overflow exception.
         Example - Getting factorial of a number using head recursion function.
      def factorial(n: Int): Int = {
       if (n == 0) 1 else n * factorial(n - 1)
      }

      Println(factorial(4))

Tail Recursion: 
  • A function in which the last action/statement is the call to the recursive function is called tail function. 
  • The function may be calling the same function of some other recursive function defined in it.
  • Tail Recursion is the specialized type of recursion that doesn't stores values in stack memory.
  • The benefit of tail recursion is it avoids the possibility of stack memory overflow exception.
          Example - Getting factorial of a number using tail recursion function.

     def factorial(n: Int): Int = {
     // @tailrec
      def iter(x: Int, result: Int): Int =
       if (x == 0) result
       else iter(x-1, result * x)
       iter(n, 1)
      }

     Println(factorial(4))
        }

N.B - This tag @tailrec in Scala ensure the function is tail recursive. If the annotation is given and if the implementation is not rail recursive then it will throw an error.

Different between function and method in functional programming :
Location: India

Comments

Post a Comment

Popular posts from this blog

Null check of Object and Object Chain in Java

Image
JDK 7 and earlier: Avoid using null check in if statement. Use ternary operator for null/exist check and assign a default value before using. This will make the code clear and more understandable as comparable to using multiple if, else   statements. JDK 8 and above : Java-8 provides improved API to deal with object null check. Use isPresent() function available in Java.util.Optional interface for null check of single object. Ex – Employee employee = new Employee(); employee .setName( "Pramoda" ); // Getting optional value Optional<Employee> optionalEmployee = Optional. ofNullable ( employee ) .map(Root::getEmployee); System. out .println( "Is Employee present : + optionalemployee .isPresent()); Use Java.util.Optional functional interface for object null check and assign default value to avoid null pointer exception. Ex – Employee employee = new Employee(); employee .setNa...
Read more

Functional Programming

Image
Functional programming is a software development paradigm out of various available software development methodology. It is based on function which is nothing but a computation unit and it's result depends on the argument and variable defined in the scope. In computer program, a functional programming treats every computation as an evaluation of mathematical functions and never use mutable data to change it's state. The output value of a pure function depends on the arguments which are input to the function and will produce the same result every time for the same set of inputs.  It means f(x) will always produce the same result y for same value of x. A function is full of functions or declarations instead of statements. Languages: Scala, Python, Erlang, Haskell etc. Various concepts of functional programming : Higher Order Functions First Class Function  Pure Function Immutability     
Read more