[Compose] 17. List comprehensions with Applicative Functors

Posted 2021-02-11 Answer1215

We annihilate the need for the ol‘ nested for loop using Applicatives.

 

For example we have this kind of nested loop code:

for(x in xs){
  for(x in ys){
     for(z in zs){

      }
  }
}

 

We can refactor it by using List comprehension:

const {List} = Immutable;
const res1 = List.of(x => x).ap(List([1,2,3]));
console.log(res1) // List [ 1,2,3 ]

 

const res1 = List.of(x => y=> `${x} - ${y}`)
      .ap(List([‘teeshirt‘, ‘sweater‘]))
      .ap(List([‘large‘, ‘medium‘, ‘small‘]));
console.log(res1) //List [ "teeshirt - large", "teeshirt - medium", "teeshirt - small", "sweater - large", "sweater - medium", "sweater - small" ]