Example of Cats Foldable usage

CatFold.scala

import cats._
import cats.data._
import cats.syntax._
import cats.implicits._

object CatFold extends App{

    // list of Tuple[Int, Double]
  println(List((20,1.1),(29,2.2)).combineAllOption)

  case class Thing[A, B](a: A, b: B)

  //implicit val thingSemigroup=Semigroup.instance[Thing[Int, BigDecimal]]( (t1, t2)=> Thing(t1.a+t2.a, t1.b+t2.b))
  //implicit val thingSemigroup2=Semigroup.instance[Thing[Int, Double]]( (t1, t2)=> Thing(t1.a+t2.a, t1.b+t2.b))

  // this replaces the above 2 lines in a more generic manner
  implicit def thingSemigroup3[A: Semigroup, B: Semigroup]=Semigroup.instance[Thing[A, B]]( (t1, t2)=> Thing(t1.a.combine(t2.a), t1.b.combine(t2.b)))

  println(List(Thing(10,BigDecimal(1.1)), Thing(29,BigDecimal(2.2))).combineAllOption)

  println(List(Thing(20,1.1), Thing(29,2.2)).combineAllOption)

  println(List(Thing("20",1.1), Thing("29",2.2)).combineAllOption)

  println("int list")

  implicit val foldableList=Foldable[List]
  val li=List(10,20,30,50,40)

  println(li.get(2))
  println(foldableList.get(li)(2))
  println(foldableList.size(li))
  println(foldableList.isEmpty(li))

  println(foldableList.combineAll(li))
  println(li.combineAll)

  println(foldableList.count(li)(_>15))
  println(li.count(_>15))

  println(foldableList.find(li)(_>15))
  println(li.find(_>15))

  println(foldableList.maximumOption(li))
  println(li.maximumOption)

}

output.txt

Some((49,3.3000000000000003))
Some(Thing(39,3.3))
Some(Thing(49,3.3000000000000003))
Some(Thing(2029,3.3000000000000003))
int list
Some(30)
Some(30)
5
false
150
150
4
4
Some(20)
Some(20)
Some(50)
Some(50)