/
comprehension.scala
158 lines (144 loc) · 6.03 KB
/
comprehension.scala
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package com.thoughtworks.dsl
import scala.language.higherKinds
import scala.language.implicitConversions
import com.thoughtworks.dsl.keywords._
private[dsl] sealed trait LowPriorityComprehension0 {
import com.thoughtworks.dsl.comprehension._
implicit def comprehensionOps[From, Keyword, Value](from: From)(
implicit asKeyword: From => Dsl.Keyword[Keyword, Value] with Keyword): ComprehensionOps[Keyword, Value] =
new ComprehensionOps[Keyword, Value](from)
}
/** Provides utilities to perform `for`-comprehension on [[Dsl.Keyword]].
*
*
* Add the following import statement to enable `for`-comprehension on keywords:
*
* {{{
* import com.thoughtworks.dsl.comprehension._
* }}}
*
* @example `for` / `yield` expressions can be used on keywords.
*
* {{{
* import com.thoughtworks.dsl.keywords._
*
* def cartesianProduct = for {
* i <- Each(Array(1, 2, 3))
* j <- Each(Vector(1, 10, 100, 1000))
* } yield i * j
* }}}
*
* The results of `for` / `yield` expressions are also keywords.
*
* {{{
* cartesianProduct should be(a[Dsl.Keyword[_, _]])
* }}}
*
* You can use !-notation extract the value from the produced keyword.
*
* {{{
* def resultAsList = List(!cartesianProduct)
* resultAsList should be(List(1, 10, 100, 1000, 2, 20, 200, 2000, 3, 30, 300, 3000))
*
* def resultAsSet: Set[Int] = !Return(!cartesianProduct)
* resultAsSet should be(Set(1, 10, 100, 1000, 2, 20, 200, 2000, 3, 30, 300, 3000))
* }}}
*
* Alternatively, [[comprehension.ComprehensionOps.to]] can be used to convert the result of a keyword to other types of values as well.
*
* {{{
* cartesianProduct.to[List] should be(List(1, 10, 100, 1000, 2, 20, 200, 2000, 3, 30, 300, 3000))
* }}}
* @example This example implements the same feature as the example on Scaladoc of [[keywords.Yield]],
* except this example use `for`-comprehension instead of !-notation.
*
* {{{
* import com.thoughtworks.dsl.Dsl
* import com.thoughtworks.dsl.keywords._
* import com.thoughtworks.dsl.comprehension._
*
* def gccFlagBuilder(sourceFile: String, includes: String*) = {
* for {
* _ <- Yield("gcc")
* _ <- Yield("-c")
* _ <- Yield(sourceFile)
* include <- Each(includes)
* _ <- Yield("-I")
* _ <- Yield(include)
* r <- Continue
* } yield r: String
* }
*
* gccFlagBuilder("main.c", "lib1/include", "lib2/include").to[Stream] should be(Stream("gcc", "-c", "main.c", "-I", "lib1/include", "-I", "lib2/include"))
* }}}
*
* Alternatively, you can use Scala native `yield` keyword to produce the last value.
*
* {{{
* def gccFlagBuilder2(sourceFile: String, includes: String*) = {
* for {
* _ <- Yield("gcc")
* _ <- Yield("-c")
* _ <- Yield(sourceFile)
* include <- Each(includes)
* _ <- Yield("-I")
* } yield include
* }
* gccFlagBuilder2("main.c", "lib1/include", "lib2/include").to[Stream] should be(Stream("gcc", "-c", "main.c", "-I", "lib1/include", "-I", "lib2/include"))
* }}}
*
* You can also omit the explicit constructor of [[keywords.Yield]] with the help of implicit conversion [[keywords.Yield.implicitYield]].
*
* {{{
* import com.thoughtworks.dsl.keywords.Yield.implicitYield
*
* def augmentString = ()
* def wrapString = ()
* }}}
*
* Note that [[scala.Predef.augmentString]] and [[scala.Predef.wrapString]] must be disabled in order to use `flatMap` for [[keywords.Yield]].
*
* {{{
* def gccFlagBuilder3(sourceFile: String, includes: String*) = {
* for {
* _ <- "gcc"
* _ <- "-c"
* _ <- sourceFile
* include <- Each(includes)
* _ <- "-I"
* } yield include
* }
* gccFlagBuilder3("main.c", "lib1/include", "lib2/include").to[Stream] should be(Stream("gcc", "-c", "main.c", "-I", "lib1/include", "-I", "lib2/include"))
* }}}
*
*/
object comprehension extends LowPriorityComprehension0 {
@inline
private def resetDomain[Keyword, Domain](keyword: Keyword)(implicit dsl: Dsl[Keyword, Domain, Domain]): Domain = {
dsl.cpsApply(keyword, implicitly)
}
final class ComprehensionOps[Keyword, Value] private[dsl] (private val keyword: Keyword) extends AnyVal {
import keywords._
def map[MapResult](mapper: Value => MapResult): Map[Keyword, Value, MapResult] = Map(keyword, mapper)
def flatMap[MapResult, NestedKeyword, NestedValue](mapper: Value => MapResult)(
implicit asKeywordMapper: (
Value => MapResult) => Value => Dsl.Keyword[NestedKeyword, NestedValue] with NestedKeyword)
: FlatMap[Keyword, Value, NestedKeyword, NestedValue] = FlatMap(keyword, mapper)
def withFilter(condition: Value => Boolean): WithFilter[Keyword, Value] = WithFilter(keyword, condition)
def to[Output[_]](implicit dsl: Dsl[Keyword, Output[Value], Value],
returnDsl: Dsl[Return[Value], Output[Value], Nothing]): Output[Value] = {
dsl.cpsApply(keyword, { value: Value =>
resetDomain(Return(value))
})
}
def as[Domain](implicit dsl: Dsl[Keyword, Domain, Value],
returnDsl: Dsl[Return[Value], Domain, Nothing]): Domain = {
dsl.cpsApply(keyword, { value: Value =>
resetDomain(Return(value))
})
}
}
implicit def nothingComprehensionOps[From, Keyword](from: From)(
implicit asKeyword: From => Dsl.Keyword[Keyword, Nothing] with Keyword): ComprehensionOps[Keyword, Nothing] =
new ComprehensionOps[Keyword, Nothing](from)
}