gistfile1.scala

import scalaz._                                                                   
import Scalaz._                                    
 
class InvoiceValidations {                                                            
  def checkName(name: String): ValidationNel[String, String] = {                      
    if (name.length > 100)                                                            
      "name too long".failNel                                                
    else                                                                  
      name.successNel                       
  }

  def withValidations(id: Int, recipient: String): ValidationNel[String, Invoice] = {
    // This one needed the [String] type parameter because it's the first one in the list
    (id.successNel[String] |@| checkName(recipient)) { Invoice(_, _) }  

    // (checkName(recipient) |@| id.successNel) { (name, id) => Invoice(id, name) }
  }
}

case class Invoice(id: Int, recipient: String)                                  
object Invoice extends InvoiceValidations

val invoice = Invoice.withValidations(1, "Louis Salin")
println(invoice)

// returns Success(Invoice(1,Louis Salin))
// if the name length is greater than 100, it returns Failure(NonEmptyList(name too long))