sample code for Cats MTL FunctorRaise

functorRaise.sc

import cats.mtl.FunctorRaise
import cats.syntax.applicative._
import cats.instances.string._
import cats.{Applicative, Semigroupal}
import cats.data.Validated

def parseNumber[F[_]: Applicative](in: String)(implicit F: FunctorRaise[F, String]): F[Double] =
  if (in.matches("-?[0-9]+")) in.toDouble.pure[F]
  else                        F.raise(in) // raise 構文

import cats.mtl.instances.handle._

val result: Validated[String, (Double, Double, Double)] = Semigroupal.tuple3(
  parseNumber[Validated[String, ?]]("abc"),
  parseNumber[Validated[String, ?]]("123"),
  parseNumber[Validated[String, ?]]("xyz")
)
// result = Invalid(abcxyz)