Functional Programming explained to my grandma


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Currying is one of the words you will hear the most when you start to work with functional programming. It is also one of the hardest to figure out.

  • Definition: Currying is the technique of translating the evaluation of a function which takes multiple arguments into evaluating a sequence of functions, each with a single argument *

We can see currying as a series of partial application.

For a function who has N parameters, a partial application will have N-X. It improves code readability by binding some parameters and giving names to specific uses.

Implement the area computation
package example
* Created by charlotte on 15/06/17.
object Area {
def area(x : Double, y:Double):Double =(x, y) match { // it's pattern matching
// you can use it to define some differents implementations
// as a function of the parameters
case (_, math.Pi) => x*x*math.Pi // for example here you can define a specific implementation for circles
case (_, _) if x>0 && y>0 => y*x //and another one for rectangle
def circleArea(radius: Double): Double= ??? //TODO Compute the circle area using the existing method
def squareArea(side: Double): Double= ??? //TODO Compute the square area using the existing method
//let's create circleArea and squareArea from the area function

Now we have seen what is partial application, we can introduce currying as a series of partial application, where at each step we only apply one parameter.


Implement the multiply and multiplyByTwo
package example
* Created by charlotte on 13/05/17.
object CurryingObject {
def multiply(x : Int, y: Int):Int= x*y //TODO define a function who multiply x by y
def multiplyByTwo(x:Int) = ??? //TODO define a function who multiply x by y
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