fix mistake in concurrency.Task5

Author: eupp

src/main/kotlin/cub/concurrent/answers/Task5.kt

@@ -30,18 +30,18 @@ class TransactionalBankAccount : BankAccount {
     override val balance: Int
         get() = account.get().balance
 
-    fun <T> transaction(block: BankAccount.() -> T): T {
-        var result: T
+    fun transaction(block: BankAccount.() -> Boolean): Boolean {
         do {
             val currentAccount = account.get()
             val newAccount = currentAccount.copy()
-            result = block(newAccount)
+            if (!block(newAccount))
+                return false
         } while (!account.compareAndSet(currentAccount, newAccount))
-        return result
+        return true
     }
 
     override fun deposit(amount: Int) {
-        transaction { deposit(amount) }
+        transaction { deposit(amount); true }
     }
 
     override fun withdraw(amount: Int): Boolean {
@@ -57,6 +57,16 @@ fun TransactionalBankAccount.buyWithCashback(price: Int, cashbackPercentage: Int
     } else false
 }
 
+fun transactionalBankAccountTest0() {
+    val account = TransactionalBankAccount()
+    account.deposit(1_500)
+    account.transaction {
+        withdraw(1_000)
+        withdraw(1_000)
+    }
+    check(account.balance == 1_500)
+}
+
 fun transactionalBankAccountTest1() {
     val account = TransactionalBankAccount()
     val t1 = thread {
@@ -110,6 +120,7 @@ fun transactionalBankAccountTest3() {
 }
 
 fun main() {
+    transactionalBankAccountTest0()
     transactionalBankAccountTest1()
     transactionalBankAccountTest2()
     transactionalBankAccountTest3()

src/main/kotlin/cub/concurrent/tasks/Task5.kt

@@ -48,12 +48,12 @@ class TransactionalBankAccount : BankAccount {
     override val balance: Int
         get() = TODO()
 
-    fun <T> transaction(block: BankAccount.() -> T): T {
+    fun transaction(block: BankAccount.() -> Boolean): Boolean {
         TODO()
     }
 
     override fun deposit(amount: Int) {
-        transaction { deposit(amount) }
+        transaction { deposit(amount); true }
     }
 
     override fun withdraw(amount: Int): Boolean {
@@ -62,6 +62,16 @@ class TransactionalBankAccount : BankAccount {
 
 }
 
+fun transactionalBankAccountTest0() {
+    val account = TransactionalBankAccount()
+    account.deposit(1_500)
+    account.transaction {
+        withdraw(1_000)
+        withdraw(1_000)
+    }
+    check(account.balance == 1_500)
+}
+
 fun transactionalBankAccountTest1() {
     val account = TransactionalBankAccount()
     val t1 = thread {
@@ -115,6 +125,7 @@ fun transactionalBankAccountTest3() {
 }
 
 fun main() {
+    transactionalBankAccountTest0()
     transactionalBankAccountTest1()
     transactionalBankAccountTest2()
     transactionalBankAccountTest3()