ThoughtWorksInc/Dsl.scala/com.thoughtworks.dsl/com.thoughtworks.dsl.domains

com.thoughtworks.dsl.domains

package com.thoughtworks.dsl.domains

Members list

Type members

Classlikes

Attributes

Source: Continuation.scala
Supertypes: class Object

trait Matchable

class Any
Self type: Continuation.type

Attributes

Authors:: 杨博 (Yang Bo)
Source: Task.scala
Supertypes: class Object

trait Matchable

class Any
Self type: Task.type

Contains interpreters to enable !-notation for Monadic and other keywords in code blocks whose type support scalaz.Bind, scalaz.MonadError and scalaz.MonadTrans.

Attributes

Authors:

杨博 (Yang Bo)

Example

scalaz.Free#Trampoline is a monadic data type that performs tail call optimization. It can be built from a @[[Dsl.reset reset]] code block within some !-notation, similar to the each method in ThoughtWorks Each.

 import _root_.scalaz.Trampoline
 import _root_.scalaz.Free.Trampoline
 import com.thoughtworks.dsl.keywords.Monadic
 import com.thoughtworks.dsl.domains.scalaz.given
 import com.thoughtworks.dsl.macros.Reset.Default.reset
 import com.thoughtworks.dsl.keywords.Monadic.unary_!
 val trampoline3 = Trampoline.done(3)
 def dslSquare = reset(Trampoline.delay {
   s"This string is produced by a trampoline: ${!trampoline3 * !trampoline3}"
 })
 dslSquare.run should be("This string is produced by a trampoline: 9")

!trampoline3 is a shortcut of !Monadic(trampoline3), enabled by import com.thoughtworks.dsl.keywords.Monadic.given, which will be converted to flatMap calls by our DSL interpreter. Thus, the method dslSquare is equivalent to the following code in scalaz.syntax:

 def scalazSyntaxSquare = trampoline3.flatMap { tmp1 =>
   trampoline3.flatMap { tmp2 =>
     Trampoline.delay {
       s"This string is produced by a trampoline: ${tmp1 * tmp2}"
     }
   }
 }
 scalazSyntaxSquare.run should be("This string is produced by a trampoline: 9")

A @[[Dsl.reset reset]] code block can contain try / catch / finally if the monadic data type supports scalaz.MonadError. tryt.scala is a monad transformer that provides scalaz.MonadError, therefore try / catch / finally expressions can be used inside a @[[Dsl.reset reset]] code block whose return type is TryT[Trampoline, ?].

 import com.thoughtworks.tryt.invariant.TryT, TryT.given
 import scala.util.{Try, Success}
 type TryTTransfomredTrampoline[A] = TryT[Trampoline, A]
 val trampolineSuccess0: TryTTransfomredTrampoline[Int] = TryT(Trampoline.done(Try(0)))
 def dslTryCatch: TryTTransfomredTrampoline[String] = reset(TryT(Trampoline.delay(Try {
   try {
     s"Division result: ${!trampoline3 / !trampolineSuccess0}"
   } catch {
     case e: ArithmeticException =>
       s"Cannot divide ${!trampoline3} by ${!trampolineSuccess0}"
   }
 })))
 inside(dslTryCatch) {
   case TryT(trampoline) =>
     trampoline.run should be(Success("Cannot divide 3 by 0"))
 }

Note that !-notation can be used on both trampoline3 and trampolineSuccess0 even when they are different types, i.e. trampoline3 is a vanilla Trampoline, while trampolineSuccess0 is a TryT-transfomred Trampoline. It is possible because the interpreters of the keywords.Monadic invoke scalaz.MonadTrans.liftM automatically. The above dslTryCatch method is equivalent to the following code in scalaz.syntax:

 import _root_.scalaz.syntax.monad._
 def scalazSyntaxTryCatch: TryTTransfomredTrampoline[String] = {
   import _root_.scalaz.syntax.monadError._
   trampoline3.liftM[TryT].flatMap { tmp0 =>
     trampolineSuccess0.flatMap { tmp1 =>
       TryT(Trampoline.delay(Try(s"Division result: ${tmp0 / tmp1}")))
     }
   }.handleError {
     case e: ArithmeticException =>
       trampoline3.liftM[TryT].flatMap { tmp2 =>
         trampolineSuccess0.flatMap { tmp3 =>
           TryT(Trampoline.delay(Try(s"Cannot divide ${tmp2} by ${tmp3}")))
         }
       }
     case e =>
       e.raiseError[TryTTransfomredTrampoline, String]
   }
 }
 inside(scalazSyntaxTryCatch) {
   case TryT(trampoline) =>
     trampoline.run should be(Success("Cannot divide 3 by 0"))
 }

Source

scalaz.scala

Supertypes

class Object

trait Matchable

class Any

Self type

scalaz.type

Types

Attributes

Source: Continuation.scala

The asynchronous task that supports exception handling, resource management, and is stack-safe.

Attributes

Example

A Task can be created from for-comprehension, where keywords.Each can be used together to asynchronously iterate collections. For example, the above concatenateRemoteData downloads and concatenates data from multiple URLs.

         import com.thoughtworks.dsl._
         import com.thoughtworks.dsl.keywords._
         import com.thoughtworks.dsl.domains.Task
         import java.net.URL
         def concatenateRemoteData(urls: List[URL], downloader: URL => Task[Vector[Byte]]) = Each.ToView {
           for {
             url <- Each(urls)
             data <- Shift(downloader(url))
             byte <- Each(data)
           } yield byte
         }.to[Task]

A Task can be also created from Task.apply

         def mockDownloader(url: URL) = Task {
           "mock data\n".getBytes.toVector
         }

A Task can be then converted to scala.concurrent.Future via Task.toFuture, in order to integrate into other frameworks. In this example, it's a Future[Assertion] required by org.scalatest.freespec.AsyncFreeSpec.

         val mockUrls = List(new URL("http://example.com/file1"), new URL("http://example.com/file2"))
         import org.scalatest.Assertion
         def assertion: Task[Assertion] = Task {
           new String((!Shift(concatenateRemoteData(mockUrls, mockDownloader))).toArray) should be("mock data\nmock data\n")
         }
         Task.toFuture(assertion)

Source

Task.scala

In this article

Generated with