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scalaz.scala
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scalaz.scala
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package com.thoughtworks.dsl
package domains
import com.thoughtworks.dsl.Dsl
import scala.language.higherKinds
import scala.language.implicitConversions
import _root_.scalaz.{Applicative, Bind, Monad, MonadError, MonadTrans}
import com.thoughtworks.dsl.keywords.{Monadic, Return}
import scala.util.control.Exception.Catcher
import scala.util.control.NonFatal
/** Contains interpreters to enable [[Dsl.Keyword#unary_$bang !-notation]] for
* [[keywords.Monadic Monadic]] and other keywords in code blocks whose type
* support [[scalaz.Bind]], [[scalaz.MonadError]] and [[scalaz.MonadTrans]].
*
* @example
* [[scalaz.Free#Trampoline]] is a monadic data type that performs tail call
* optimization. It can be built from a `@[[Dsl.reset reset]]` code block
* within some [[Dsl.Keyword#unary_$bang !-notation]], similar to the
* [[com.thoughtworks.each.Monadic.EachOps#each each]] method in
* [[https://github.com/ThoughtWorksInc/each 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]].
* [[https://github.com/ThoughtWorksInc/tryt.scala 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 ${!trampolineSuccess0}"
* }
* })))
*
* inside(dslTryCatch) {
* case TryT(trampoline) =>
* trampoline.run should be(Success("Cannot divide 3 by 0"))
* }
* }}}
* Note that [[Dsl.Keyword#unary_$bang !-notation]] can be used on both
* `trampoline3` and `trampolineSuccess0` even when they are different types,
* i.e. `trampoline3` is a vanilla [[scalaz.Free.Trampoline Trampoline]],
* while `trampolineSuccess0` is a
* [[com.thoughtworks.tryt.invariant.TryT TryT]]-transfomred
* [[scalaz.Free.Trampoline Trampoline]]. It is possible because the
* interpreters of the [[keywords.Monadic]] invoke
* [[scalaz.MonadTrans.liftM]] automatically. <p> 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"))
* }
* }}}
*
* @author
* 杨博 (Yang Bo)
*/
object scalaz extends scalaz.LowPriority0 {
protected type MonadThrowable[F[_]] = MonadError[F, Throwable]
@inline private def catchNativeException[F[_], A](
continuation: F[A] !! A
)(implicit monadThrowable: MonadThrowable[F]): F[A] = {
try {
continuation(monadThrowable.pure(_))
} catch {
case NonFatal(e) =>
monadThrowable.raiseError(e)
}
}
given [F[_], A, B](using
monadError: MonadThrowable[F]
): keywords.TryCatch.DslComposer[F[B], A, F[A]] =
keywords.TryCatch.DslComposer {
[BlockKeyword, CaseKeyword] =>
(
blockDsl: Dsl.Searching[BlockKeyword, F[A], A],
caseDsl: Dsl.Searching[CaseKeyword, F[A], A]
) ?=>
Dsl.Composed[keywords.TryCatch[BlockKeyword, CaseKeyword], F[B], A] {
case (keywords.TryCatch(block, catcher), outerSuccessHandler) =>
import monadError.monadErrorSyntax._
val blockDomain =
try {
summon[Dsl.Run[BlockKeyword, F[A], A]](block())
} catch {
case NonFatal(e) =>
monadError.raiseError(e)
}
blockDomain
.handleError {
case catcher(recovered) =>
summon[Dsl.Run[CaseKeyword, F[A], A]](recovered)
case e: Throwable =>
throw e
}
.flatMap(outerSuccessHandler)
}
}
private[scalaz] trait LowPriority0:
/** The [[Dsl]] instance that converts a keyword to the monad domain type
* then flatMap. This instance helps when the keyword supports a domain `D`
* that can be lifted to the `F[A]`, while there is not general rule to
* derive `F[A]` from `D`. For example, when `F[A]` is a monad transformer
* and `D` is the underlying monad type.
*/
given [F[_], K, A, G[_], B](using
monad: Monad[F],
lift: Dsl.Lift[G[A], F[A]],
dsl: Dsl.Searching[K, G[A], A],
liftG: Dsl.Lift[A, G[A]]
): Dsl.Derived.StackUnsafe[K, F[B], A] =
Dsl.Derived.StackUnsafe { (keyword: K, handler: A => F[B]) =>
monad.bind(lift(dsl(keyword, liftG)))(
handler
)
}
given [F[_], A, B](using
applicative: Applicative[F]
): Dsl.Lift.OneStep[A, F[A]] =
applicative.pure
given [F[_[_], _], G[_], A, B](using
monadTrans: MonadTrans[F],
monad: Monad[G]
): Dsl.Lift.OneStep[G[A], F[G, A]] = {
monadTrans.liftM(_)
}
/** The [[Dsl]] instance that converts a [[domains.Monadic]] keyword to the
* monad domain type then flatMap. This instance helps when the keyword
* supports a domain `D` that can be lifted to the `F[A]`, while there is not
* general rule to derive `F[A]` from `D`. For example, when `F[A]` is a
* monad transformer and `D` is the underlying monad type.
*/
given [F[_], A, G[_], B](using
monad: Bind[F],
lift: Dsl.Lift[G[A], F[A]]
): Dsl.Original[Monadic[G[A]], F[B], A] =
Dsl.Original { (keyword: Monadic[G[A]], handler: A => F[B]) =>
monad.bind(lift(Monadic.flip(keyword)))(
handler
)
}
}