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douglas-vaz/compose.scala

Created February 9, 2018 14:00
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Scala compose monadic type
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compose.scala
implicit class OptionK[A, B](f: (A) => Option[B]) {
def composed[C](g: B => Option[C]): (A) => Option[C] = (x: A) => f(x).flatMap(g)
}
val strToInt:(String) => Option[Int] = s => if(s.matches("-?[\\d]+")) Some(s.toInt) else None
val realSqrt:(Int) => Option[Double] = x => if(x > 0) Some(Math.sqrt(x)) else None
val strToSqrt = strToInt composed realSqrt
strToSqrt("9") //Some(3.0)
strToSqrt("-9") //None
strToSqrt("meh") //None
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