Scalaz Logger monad example

gistfile1.scala

type StringLogger[A] = Logger[String, A]

def startWith(i: Int): StringLogger[Int] = i.logger :+-> "Started with " + i

def thenAdd(j: Int)(i: Int): StringLogger[Int] = (i + j).logger :+-> "Added " + j

def thenMultBy(j: Int)(i: Int): StringLogger[Int] = (i * j).logger :+-> "Multiplied by " + j

val loggedResult = startWith(1) >>= thenAdd(4) >>= thenMultBy(5)

loggedResult.over
// res0: Int = 25

loggedResult.log.toList
// res1: List[String] = List(Started with 1, Added 4, Multiplied by 5)