Scalaz Validation and For-comprehension

validation-and-for-comp

#!/usr/bin/env scalas

/***
scalaVersion := "2.11.0"

scalacOptions += "-language:_"

libraryDependencies += "org.scalaz" %% "scalaz-core" % "7.0.6"
*/

import scala.math.sqrt

import scalaz._, Scalaz._

def sqroot(d: Double): Validation[String, Double] = if (d >=0) sqrt(d).success else s"$d lt 0".fail

def inverse(d: Double): Validation[String, Double] = if (d == 0) "is 0".fail else (1 / d).success

def compute(d: Double): Validation[String, Double] =
    for {
        x <- sqroot(d)
        y <- inverse(x)
    } yield y

println(compute(-1.0))
println(compute(0.0))
println(compute(2.0))