Functional Programming explained to my grandma

Anne-Honyme
1,590 views

Open Source Your Knowledge, Become a Contributor

Technology knowledge has to be shared and made accessible for free. Join the movement.

Create Content

Currying

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
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
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
}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

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.

Example

Implement the multiply and multiplyByTwo
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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
}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Open Source Your Knowledge: become a Contributor and help others learn. Create New Content