com.thoughtworks.dsl.keywords

The following readAll is a Task to read file content with the help of AsynchronousIo.ReadFile

        import java.nio._, file._, channels._
        import com.thoughtworks.dsl.bangnotation._
        import com.thoughtworks.dsl.comprehension._
        import com.thoughtworks.dsl.domains.Task
        import com.thoughtworks.dsl.keywords._
        import com.thoughtworks.dsl.keywords.Shift._
        import com.thoughtworks.dsl.keywords.AsynchronousIo.ReadFile
        import scala.collection.mutable.ArrayBuffer
        import scala.io.Codec
        def readAll(channel: AsynchronousFileChannel, temporaryBufferSize: Int = 4096): Task[ArrayBuffer[CharBuffer]] = *[Task] {
          val charBuffers = ArrayBuffer.empty[CharBuffer]
          val decoder = Codec.UTF8.decoder
          val byteBuffer = ByteBuffer.allocate(temporaryBufferSize)
          var position: Long = 0L
          while (!ReadFile(channel, byteBuffer, position) != -1) {
            position += byteBuffer.position()
            byteBuffer.flip()
            charBuffers += decoder.decode(byteBuffer)
            byteBuffer.clear()
          }
          charBuffers
        }

    `Task`s created from !-notation can be used in `for`-comprehension,
    and other keywords can be used together in the same `for` block.
    For example, the following `cat` function contains a single `for` block to concatenate file contents.
    It asynchronously iterates elements `Seq`, `ArrayBuffer` and `String` with the help of [[keywords.Each]],
    managed native resources with the help of [[keywords.Using]],
    performs previously created `readAll` task with the help of [[keywords.Shift]],
    and finally converts the return type [[comprehension.ComprehensionOps.as as]] a `Task[Vector[Char]]`.

        import com.thoughtworks.dsl._
        import com.thoughtworks.dsl.bangnotation._
        import com.thoughtworks.dsl.keywords._
        import com.thoughtworks.dsl.keywords.Shift._
        import com.thoughtworks.dsl.domains.Task
        import java.net.URL
        def cat(paths: Path*) = {
          for {
            path <- Each(paths)
            channel <- Using(AsynchronousFileChannel.open(path))
            charBuffers <- Shift(readAll(channel))
            charBuffer <- Each(charBuffers)
            char <- Each(charBuffer.toString)
          } yield char
        }.as[Task[Vector[Char]]]

    Then the `cat` function is used to concatenate files from this project, as shown below:

        Task.toFuture(*[Task] {
          (!Shift(cat(Paths.get(".sbtopts"), Paths.get(".scalafmt.conf")))).mkString should be(
            "-J-XX:MaxMetaspaceSize=512M\n-J-Xmx5G\n-J-Xss6M\nversion = \"1.5.1\"\nmaxColumn = 120"
          )
        })

The Continue object, which is the only instance of this Continue class.

杨博 (Yang Bo)

Each for creating collection comprehensions.

This Continue keyword is usually used with Each, to skip an element in the loop.

Each and Continue can be used to calculate composite numbers and prime numbers.

        import com.thoughtworks.dsl.bangnotation._
        def compositeNumbersBelow(maxNumber: Int) = *[collection.immutable.HashSet] {
          val factor = !Each(2 until math.ceil(math.sqrt(maxNumber)).toInt)
          !Each(2 * factor until maxNumber by factor)
        }
        compositeNumbersBelow(13) should be(Set(4, 6, 8, 9, 10, 12))
        def primeNumbersBelow(maxNumber: Int) = *[Seq] {
          val compositeNumbers = compositeNumbersBelow(maxNumber)
          val i = !Each(2 until maxNumber)
          if (compositeNumbers(i)) !Continue
          i
        }
        primeNumbersBelow(13) should be(Array(2, 3, 5, 7, 11))

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comprehension if you want to use traditional for comprehension instead of !-notation.

Each keywords can be used to calculate cartesian product.

        import com.thoughtworks.dsl.bangnotation._
        def cartesianProduct = reset (List(!Each(Array(1, 2, 3)) * !Each(Vector(1, 10, 100, 1000))))
        cartesianProduct should be(List(1, 10, 100, 1000, 2, 20, 200, 2000, 3, 30, 300, 3000))

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Put

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Get

The following example creates a function that accepts a string parameter and returns the upper-cased last character of the parameter.

import com.thoughtworks.dsl.bangnotation.{unary_!, reset}
def upperCasedLastCharacter = reset[String => Char] {
 val initialValue = !Get[String]()
 !Put(initialValue.toUpperCase)
 val upperCased = !Get[String]()
 Function.const(upperCased.last)
}

For example, given a string of foo, the upper-cased last character should be O.

upperCasedLastCharacter("foo") should be('O')

Put and Get support multiple states. The following code creates a formatter that Put parts of content into a Vector[Any] of string buffers.

import com.thoughtworks.dsl.bangnotation.{reset, unary_!}
def formatter = reset[Double => Int => Vector[Any] => String] {
 !Put(!Get[Vector[Any]]() :+ "x=")
 !Put(!Get[Vector[Any]]() :+ !Get[Double]())
 !Put(!Get[Vector[Any]]() :+ ",y=")
 !Put(!Get[Vector[Any]]() :+ !Get[Int]())
 !Return((!Get[Vector[Any]]()).mkString)
}
formatter(0.5)(42)(Vector.empty) should be("x=0.5,y=42")

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Given a Future:

import com.thoughtworks.dsl.bangnotation._
import scala.concurrent.Future
val myFuture40 = Future {
 40
}

You can Await the Future in another Future

def myFuture42 = *[Future] {
 !Await(myFuture40) + 2
}

A Future can be converted to a domains.task.Task with the help of Await.

import com.thoughtworks.dsl.domains.Task
import com.thoughtworks.dsl.keywords.Await
val myTask = *[Task] {
 !Await(myFuture42)
}

Then a domains.task.Task can be converted back to a scala.concurrent.Future via domains.task.Task.toFuture.

val myAssertionTask = *[Task] {
 !Shift(myTask) should be(42)
}
Task.toFuture(myAssertionTask)

!Await can be used together with try / catch / finally.

import scala.concurrent.Future
import com.thoughtworks.dsl.bangnotation._
val buffer = new StringBuffer
def recoverFuture = Future {
 buffer.append("Oh")
}
def exceptionalFuture = Future[StringBuffer] {
 throw new IllegalStateException("No")
}
def myFuture = *[Future] {
 try {
   !Await(exceptionalFuture)
 } catch {
   case e: IllegalStateException =>
     !Await(recoverFuture)
     buffer.append(' ')
     buffer.append(e.getMessage)
 } finally {
   buffer.append("!")
 }
}
myFuture.map(_.toString should be("Oh No!"))

Other keywords, including Return or Get, can be used together with Await

import scala.concurrent.Future
import com.thoughtworks.dsl.keywords.{Get, Return}
import com.thoughtworks.dsl.bangnotation._
val buffer = new StringBuffer
def recoverFuture = Future {
 buffer.append("Oh")
}
def exceptionalFuture = Future[StringBuffer] {
 throw new IllegalStateException("No")
}
def myFuture = reset[Char => Future[StringBuffer]](!Return {
 try {
   !Await(exceptionalFuture)
 } catch {
   case e: IllegalStateException =>
     !Await(recoverFuture)
     buffer.append(!Get[Char]())
     buffer.append(e.getMessage)
 } finally {
   buffer.append("!")
 }
})
myFuture(' ').map(_.toString should be("Oh No!"))

com.thoughtworks.dsl.domains.cats for using this Monadic keyword with cats.Monad.

com.thoughtworks.dsl.domains.scalaz for using this Monadic keyword with scalaz.Monad.

Monadic should be a scala.AnyVal after https://github.com/scala/bug/issues/10595 is resolved.

杨博 (Yang Bo)

杨博 (Yang Bo)

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dsl for usage of this Using keyword in continuations

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comprehension if you want to use traditional for comprehension instead of !-notation.

This Yield keyword must be put inside a function that returns Seq[Element] or Seq[Element] !! ..., or it will not compile.

        import com.thoughtworks.dsl.bangnotation._
        "def f(): Int = !Yield(1)" shouldNot compile

Yield keywords can be used together with other keywords.

        import com.thoughtworks.dsl.bangnotation._
        def gccFlagBuilder(sourceFile: String, includes: String*) = reset[Stream[String]] {
          !Yield("gcc")
          !Yield("-c")
          !Yield(sourceFile)
          val include = !Each(includes)
          !Yield("-I")
          !Yield(include)
          !Continue
        }
        gccFlagBuilder("main.c", "lib1/include", "lib2/include") should be(Stream("gcc", "-c", "main.c", "-I", "lib1/include", "-I", "lib2/include"))