diff --git a/.gitignore b/.gitignore
index f4611fa..bfc8281 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,3 +17,6 @@ project/plugins/project/
 # Scala-IDE specific
 .scala_dependencies
 .worksheet
+
+# IntelliJ specific
+.idea
diff --git a/src/main/scala/frdomain/ch6/domain/app/app.scala b/src/main/scala/frdomain/ch6/domain/app/app.scala
index de0a6bf..9533dd9 100644
--- a/src/main/scala/frdomain/ch6/domain/app/app.scala
+++ b/src/main/scala/frdomain/ch6/domain/app/app.scala
@@ -6,36 +6,33 @@ import scalaz._
 import Scalaz._
 import Kleisli._
 import scala.concurrent._
-import ExecutionContext.Implicits.global
 
 import service.interpreter.{ AccountService, InterestPostingService, ReportingService }
 import repository.interpreter.AccountRepositoryInMemory
 import service.{ Checking, Savings }
-import model.common._
-import model.Account
 
 object App {
 
   import AccountService._
-  import InterestPostingService._
   import ReportingService._
+  import ExecutionContext.Implicits.global
 
-  val opens = 
+  val opens =
     for {
       _ <- open("a1234", "a1name", None, None, Checking)
       _ <- open("a2345", "a2name", None, None, Checking)
       _ <- open("a3456", "a3name", BigDecimal(5.8).some, None, Savings)
       _ <- open("a4567", "a4name", None, None, Checking)
       _ <- open("a5678", "a5name", BigDecimal(2.3).some, None, Savings)
-    } yield (())
+    } yield ()
 
-  val credits = 
+  val credits =
     for {
       _ <- credit("a1234", 1000)
       _ <- credit("a2345", 2000)
       _ <- credit("a3456", 3000)
       _ <- credit("a4567", 4000)
-    } yield (())
+    } yield ()
 
   val c = for {
     _ <- opens
diff --git a/src/main/scala/frdomain/ch6/domain/app/app2.scala b/src/main/scala/frdomain/ch6/domain/app/app2.scala
index ba5aaa6..cf5a2f3 100644
--- a/src/main/scala/frdomain/ch6/domain/app/app2.scala
+++ b/src/main/scala/frdomain/ch6/domain/app/app2.scala
@@ -4,18 +4,20 @@ package app
 
 import scalaz._
 import Scalaz._
-import \/._
-
 import repository.interpreter.AccountRepositoryInMemory
 import model.common._
-import model.{ Account, Balance }
+import model.{Account, Balance}
 import Account._
+import frdomain.ch6.domain.service.Valid
 
 object App2 {
+
   import AccountRepositoryInMemory._
-  val account = checkingAccount("a-123", "debasish ghosh", today.some, None, Balance(0)).toOption.get
+  import scala.concurrent.ExecutionContext.Implicits.global
+
+  val account = checkingAccount("a-123", "debasish ghosh", today.some, None, Balance()).toOption.get
   val c = for {
-    b <- updateBalance(account, 10000)
+    b <- Valid(updateBalance(account, 10000))
     c <- store(b)
     d <- balance(c.no)
   } yield d
diff --git a/src/main/scala/frdomain/ch6/domain/model/Account.scala b/src/main/scala/frdomain/ch6/domain/model/Account.scala
index 057141d..18ddb2b 100644
--- a/src/main/scala/frdomain/ch6/domain/model/Account.scala
+++ b/src/main/scala/frdomain/ch6/domain/model/Account.scala
@@ -28,15 +28,15 @@ sealed trait Account {
 final case class CheckingAccount (no: String, name: String,
   dateOfOpen: Option[Date], dateOfClose: Option[Date] = None, balance: Balance = Balance()) extends Account
 
-final case class SavingsAccount (no: String, name: String, rateOfInterest: Amount, 
+final case class SavingsAccount (no: String, name: String, rateOfInterest: Amount,
   dateOfOpen: Option[Date], dateOfClose: Option[Date] = None, balance: Balance = Balance()) extends Account
 
 object Account {
-  private def validateAccountNo(no: String) = 
-    if (no.isEmpty || no.size < 5) s"Account No has to be at least 5 characters long: found $no".failureNel[String] 
+  private def validateAccountNo(no: String) =
+    if (no.isEmpty || no.size < 5) s"Account No has to be at least 5 characters long: found $no".failureNel[String]
     else no.successNel[String]
 
-  private def validateOpenCloseDate(od: Date, cd: Option[Date]) = cd.map { c => 
+  private def validateOpenCloseDate(od: Date, cd: Option[Date]) = cd.map { c =>
     if (c before od) s"Close date [$c] cannot be earlier than open date [$od]".failureNel[(Option[Date], Option[Date])]
     else (od.some, cd).successNel[String]
   }.getOrElse { (od.some, cd).successNel[String] }
@@ -45,26 +45,26 @@ object Account {
     if (rate <= BigDecimal(0)) s"Interest rate $rate must be > 0".failureNel[BigDecimal]
     else rate.successNel[String]
 
-  def checkingAccount(no: String, name: String, openDate: Option[Date], closeDate: Option[Date], 
-    balance: Balance): \/[NonEmptyList[String], Account] = { 
+  def checkingAccount(no: String, name: String, openDate: Option[Date], closeDate: Option[Date],
+    balance: Balance): \/[NonEmptyList[String], Account] = {
 
     val od = openDate.getOrElse(today)
 
     (
-      validateAccountNo(no) |@| 
+      validateAccountNo(no) |@|
       validateOpenCloseDate(openDate.getOrElse(today), closeDate)
     ) { (n, d) =>
       CheckingAccount(n, name, d._1, d._2, balance)
     }.disjunction
   }
 
-  def savingsAccount(no: String, name: String, rate: BigDecimal, openDate: Option[Date], 
-    closeDate: Option[Date], balance: Balance): \/[NonEmptyList[String], Account] = { 
+  def savingsAccount(no: String, name: String, rate: BigDecimal, openDate: Option[Date],
+    closeDate: Option[Date], balance: Balance): \/[NonEmptyList[String], Account] = {
 
     val od = openDate.getOrElse(today)
 
     (
-      validateAccountNo(no) |@| 
+      validateAccountNo(no) |@|
       validateOpenCloseDate(openDate.getOrElse(today), closeDate) |@|
       validateRate(rate)
     ) { (n, d, r) =>
@@ -110,5 +110,3 @@ object Account {
     case _ => None
   }
 }
-
-
diff --git a/src/main/scala/frdomain/ch6/domain/package.scala b/src/main/scala/frdomain/ch6/domain/package.scala
index e7c5ed0..427e2c4 100644
--- a/src/main/scala/frdomain/ch6/domain/package.scala
+++ b/src/main/scala/frdomain/ch6/domain/package.scala
@@ -7,4 +7,13 @@ import Scalaz._
 
 package object service {
   type Valid[A] = EitherT[Future, NonEmptyList[String], A]
+
+  object Valid {
+    implicit val validAppl = new Applicative[Valid] {
+      override def point[A](a: => A): Valid[A] = EitherT(Future.successful(a.right))
+      override def ap[A, B](fa: => Valid[A])(f: => Valid[(A) => B]): Valid[B] = ???
+    }
+
+    def apply[A](block: => NonEmptyList[String] \/ A): Valid[A] = EitherT { Future.successful(block) }
+  }
 }
diff --git a/src/main/scala/frdomain/ch6/domain/repository/AccountRepository.scala b/src/main/scala/frdomain/ch6/domain/repository/AccountRepository.scala
index ffdda0c..cebaa97 100644
--- a/src/main/scala/frdomain/ch6/domain/repository/AccountRepository.scala
+++ b/src/main/scala/frdomain/ch6/domain/repository/AccountRepository.scala
@@ -3,20 +3,26 @@ package domain
 package repository
 
 import java.util.Date
-import scalaz._
-import Scalaz._
-import \/._
-import model.{ Account, Balance }
 
-trait AccountRepository { 
-  def query(no: String): \/[NonEmptyList[String], Option[Account]]
-  def store(a: Account): \/[NonEmptyList[String], Account]
-  def balance(no: String): \/[NonEmptyList[String], Balance] = query(no) match {
-    case \/-(Some(a)) => a.balance.right
-    case \/-(None) => NonEmptyList(s"No account exists with no $no").left[Balance]
-    case a @ -\/(_) => a
+import frdomain.ch6.domain.model.{Account, Balance}
+import frdomain.ch6.domain.service.Valid
+
+import scala.concurrent.ExecutionContext.Implicits.global
+import scalaz.NonEmptyList
+import scalaz.Scalaz._
+
+trait AccountRepository {
+  def query(no: String): Valid[Option[Account]]
+  def store(a: Account): Valid[Account]
+  def query(openedOn: Date): Valid[Seq[Account]]
+  def all: Valid[Seq[Account]]
+
+  def balance(no: String): Valid[Balance] = query(no).flatMap { maybeAcc =>
+    Valid {
+      maybeAcc match {
+        case Some(acc) => acc.balance.right
+        case None => NonEmptyList(s"No account exists with no $no").left
+      }
+    }
   }
-  def query(openedOn: Date): \/[NonEmptyList[String], Seq[Account]]
-  def all: \/[NonEmptyList[String], Seq[Account]]
 }
-
diff --git a/src/main/scala/frdomain/ch6/domain/repository/interpreter/AccountRepository.scala b/src/main/scala/frdomain/ch6/domain/repository/interpreter/AccountRepository.scala
deleted file mode 100644
index f3f3fec..0000000
--- a/src/main/scala/frdomain/ch6/domain/repository/interpreter/AccountRepository.scala
+++ /dev/null
@@ -1,26 +0,0 @@
-package frdomain.ch6
-package domain
-package repository
-package interpreter
-
-import java.util.Date
-import scala.collection.mutable.{ Map => MMap }
-import scalaz._
-import Scalaz._
-import \/._
-import model.{ Account, Balance }
-
-trait AccountRepositoryInMemory extends AccountRepository {
-  lazy val repo = MMap.empty[String, Account]
-
-  def query(no: String): \/[NonEmptyList[String], Option[Account]] = repo.get(no).right
-  def store(a: Account): \/[NonEmptyList[String], Account] = {
-    val r = repo += ((a.no, a))
-    a.right
-  }
-  def query(openedOn: Date): \/[NonEmptyList[String], Seq[Account]] = repo.values.filter(_.dateOfOpen == openedOn).toSeq.right
-  def all: \/[NonEmptyList[String], Seq[Account]] = repo.values.toSeq.right
-}
-
-object AccountRepositoryInMemory extends AccountRepositoryInMemory
-
diff --git a/src/main/scala/frdomain/ch6/domain/repository/interpreter/AccountRepositoryInMemory.scala b/src/main/scala/frdomain/ch6/domain/repository/interpreter/AccountRepositoryInMemory.scala
new file mode 100644
index 0000000..7da0db0
--- /dev/null
+++ b/src/main/scala/frdomain/ch6/domain/repository/interpreter/AccountRepositoryInMemory.scala
@@ -0,0 +1,32 @@
+package frdomain.ch6
+package domain
+package repository
+package interpreter
+
+import java.util.Date
+
+import frdomain.ch6.domain.model.Account
+import frdomain.ch6.domain.service.Valid
+import frdomain.ch6.domain.service.Valid._
+
+import scala.collection.mutable.{Map => MMap}
+import scalaz.Scalaz._
+
+trait AccountRepositoryInMemory extends AccountRepository {
+  lazy val repo = MMap.empty[String, Account]
+
+  override def query(no: String): Valid[Option[Account]] = repo.get(no).pure[Valid]
+
+  override def store(a: Account): Valid[Account] = {
+    repo += ((a.no, a))
+    a.pure[Valid]
+  }
+
+  override def query(openedOn: Date): Valid[Seq[Account]] =
+    repo.values.filter(_.dateOfOpen == openedOn).toSeq.pure[Valid]
+
+  override def all: Valid[Seq[Account]] = repo.values.toSeq.pure[Valid]
+}
+
+object AccountRepositoryInMemory extends AccountRepositoryInMemory
+
diff --git a/src/main/scala/frdomain/ch6/domain/service/AccountService.scala b/src/main/scala/frdomain/ch6/domain/service/AccountService.scala
index 77db55f..0aec967 100644
--- a/src/main/scala/frdomain/ch6/domain/service/AccountService.scala
+++ b/src/main/scala/frdomain/ch6/domain/service/AccountService.scala
@@ -33,6 +33,6 @@ trait AccountService[Account, Amount, Balance] {
   def transfer(from: String, to: String, amount: Amount): AccountOperation[(Account, Account)] = for { 
     a <- debit(from, amount)
     b <- credit(to, amount)
-  } yield ((a, b))
+  } yield (a, b)
 }
 
diff --git a/src/main/scala/frdomain/ch6/domain/service/interpreter/AccountService.scala b/src/main/scala/frdomain/ch6/domain/service/interpreter/AccountService.scala
index 94a5b99..d37d7c1 100644
--- a/src/main/scala/frdomain/ch6/domain/service/interpreter/AccountService.scala
+++ b/src/main/scala/frdomain/ch6/domain/service/interpreter/AccountService.scala
@@ -3,58 +3,48 @@ package domain
 package service
 package interpreter
 
-import java.util.{ Date, Calendar }
+import java.util.{Date, Calendar}
 
 import scalaz._
 import Scalaz._
 import \/._
 import Kleisli._
 
-import scala.concurrent._
-import ExecutionContext.Implicits.global
-
-import model.{ Account, Balance }
+import model.{Account, Balance}
 import model.common._
 import repository.AccountRepository
 
+import scala.concurrent._
+import ExecutionContext.Implicits.global
+
 class AccountServiceInterpreter extends AccountService[Account, Amount, Balance] {
 
-  def open(no: String, 
-           name: String, 
+  def open(no: String,
+           name: String,
            rate: Option[BigDecimal],
            openingDate: Option[Date],
            accountType: AccountType) = kleisli[Valid, AccountRepository, Account] { (repo: AccountRepository) =>
-
-    EitherT {
-      Future {
-        repo.query(no) match {
-          case \/-(Some(a)) => NonEmptyList(s"Already existing account with no $no").left[Account]
-          case \/-(None)    => accountType match {
-            case Checking => Account.checkingAccount(no, name, openingDate, None, Balance()).flatMap(repo.store)
-            case Savings  => rate map { r =>
-              Account.savingsAccount(no, name, r, openingDate, None, Balance()).flatMap(repo.store)
-            } getOrElse {
-              NonEmptyList(s"Rate needs to be given for savings account").left[Account]
-            }
-          }
-          case a @ -\/(_) => a
+    repo.query(no) flatMap {
+      case Some(_) => Valid(NonEmptyList(s"Already existing account with no $no").left[Account])
+      case None => accountType match {
+        case Checking => Valid(Account.checkingAccount(no, name, openingDate, None, Balance())).flatMap(repo.store)
+        case Savings => rate map { r =>
+          Valid(Account.savingsAccount(no, name, r, openingDate, None, Balance())).flatMap(repo.store)
+        } getOrElse {
+          Valid(NonEmptyList(s"Rate needs to be given for savings account").left[Account])
         }
       }
     }
   }
 
-  def close(no: String, closeDate: Option[Date]) = kleisli[Valid, AccountRepository, Account] { (repo: AccountRepository) =>
-    EitherT {
-      Future {
-        repo.query(no) match {
-          case \/-(None) => NonEmptyList(s"Account $no does not exist").left[Account]
-          case \/-(Some(a)) => 
-            val cd = closeDate.getOrElse(today)
-            Account.close(a, cd).flatMap(repo.store)
-          case a @ -\/(_) => a
-        }
+  def close(no: String, closeDate: Option[Date]) = kleisli[Valid, AccountRepository, Account] {
+    (repo: AccountRepository) =>
+      repo.query(no).flatMap {
+        case None => Valid(NonEmptyList(s"Account $no does not exist").left[Account])
+        case Some(a) =>
+          val cd = closeDate.getOrElse(today)
+          Valid(Account.close(a, cd)).flatMap(repo.store)
       }
-    }
   }
 
   def debit(no: String, amount: Amount) = up(no, amount, D)
@@ -64,26 +54,20 @@ class AccountServiceInterpreter extends AccountService[Account, Amount, Balance]
   private case object D extends DC
   private case object C extends DC
 
-  private def up(no: String, amount: Amount, dc: DC): AccountOperation[Account] = kleisli[Valid, AccountRepository, Account] { (repo: AccountRepository) =>
-    EitherT {
-      Future {
-        repo.query(no) match {
-          case \/-(None) => NonEmptyList(s"Account $no does not exist").left[Account]
-          case \/-(Some(a)) => dc match {
-            case D => Account.updateBalance(a, -amount).flatMap(repo.store) 
-            case C => Account.updateBalance(a, amount).flatMap(repo.store) 
-          }
-          case a @ -\/(_) => a
+  private def up(no: String, amount: Amount, dc: DC): AccountOperation[Account] = kleisli[Valid, AccountRepository, Account] {
+    (repo: AccountRepository) =>
+      repo.query(no) flatMap {
+        case None => Valid(NonEmptyList(s"Account $no does not exist").left[Account])
+        case Some(a) => dc match {
+          case D => Valid(Account.updateBalance(a, -amount)).flatMap(repo.store)
+          case C => Valid(Account.updateBalance(a, amount)).flatMap(repo.store)
         }
       }
-    }
   }
 
-  def balance(no: String) = 
-    kleisli[Valid, AccountRepository, Balance] { (repo: AccountRepository) => 
-      EitherT {
-        Future { repo.balance(no) }
-      }
+  def balance(no: String) =
+    kleisli[Valid, AccountRepository, Balance] {
+      (repo: AccountRepository) => repo.balance(no)
     }
 }
 
diff --git a/src/main/scala/frdomain/ch6/domain/service/interpreter/ReportingService.scala b/src/main/scala/frdomain/ch6/domain/service/interpreter/ReportingService.scala
index 72807f1..a01c60a 100644
--- a/src/main/scala/frdomain/ch6/domain/service/interpreter/ReportingService.scala
+++ b/src/main/scala/frdomain/ch6/domain/service/interpreter/ReportingService.scala
@@ -16,16 +16,10 @@ import model.common._
 
 class ReportingServiceInterpreter extends ReportingService[Amount] {
 
-  def balanceByAccount: ReportOperation[Seq[(String, Amount)]] = kleisli[Valid, AccountRepository, Seq[(String, Amount)]] { (repo: AccountRepository) =>
-    EitherT {
-      Future {
-        repo.all match {
-          case \/-(as) => as.map(a => (a.no, a.balance.amount)).right
-          case a @ -\/(_) => a
-        }
-      }
+  def balanceByAccount: ReportOperation[Seq[(String, Amount)]] =
+    kleisli[Valid, AccountRepository, Seq[(String, Amount)]] { (repo: AccountRepository) =>
+      repo.all map { as => as.map(a => (a.no, a.balance.amount)) }
     }
-  }
-} 
+}
 
 object ReportingService extends ReportingServiceInterpreter