Building a DSL... In Kotlin

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PABLO GUARDIOLA Building a DSL… In Kotlin

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PABLO GUARDIOLA Building a DSL… In Kotlin

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Building a DSL… In Kotlin With KΛTEGORY PABLO GUARDIOLA

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key concepts @Guardiola31337

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key concepts @Guardiola31337 Composable

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key concepts @Guardiola31337 Composable Extensible

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key concepts @Guardiola31337 Composable Extensible Testable

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Composable Extensible Testable Integration w/ current frameworks key concepts @Guardiola31337

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dsl @Guardiola31337

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dsl (noun) “A computer programming language of limited expressiveness focused on a particular domain.” @Guardiola31337

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dsl @Guardiola31337 Programming language

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dsl @Guardiola31337 Programming language Language nature

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dsl @Guardiola31337 Programming language Language nature Limited expressiveness

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Programming language Language nature Limited expressiveness Domain focus dsl @Guardiola31337

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uiagesturegen @Guardiola31337

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uiagesturegen KΛTEGORY @Guardiola31337

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usage @Guardiola31337

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usage private fun composing(element: UiObject): Boolean { val actions = pinchOut(100, 50) .swipeDown(30) .swipeRight(30) .pinchOut(100, 50) .swipeUp(100) return actions.validate(element).hasCompletedCorrectly() } @Guardiola31337

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@Guardiola31337

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free dsl @Guardiola31337

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free dsl @Guardiola31337 Define your algebra (a.k.a. operations)

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algebra @higherkind sealed class GesturesDSL : GesturesDSLKind { data class WithView (val f: (UiObject) -> A) : GesturesDSL () object Click : GesturesDSL() object DoubleTap : GesturesDSL() data class PinchIn(val percent: Int, val steps: Int) : GesturesDSL() // ... companion object : FreeApplicativeApplicativeInstance } @Guardiola31337

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free dsl @Guardiola31337 Define your algebra (a.k.a. operations) Lift everything to the context of free

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lift fun withView(f: (UiObject) -> A): ActionDSL = FreeApplicative.liftF(GesturesDSL.WithView(f)) // ... fun ActionDSL.click(): ActionDSL = combine(this, com.pguardiola.uigesturegen.dsl.click()) fun click(): ActionDSL = FreeApplicative.liftF(GesturesDSL.Click) // ... @Guardiola31337

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lift fun ActionDSL.doubleTap(): ActionDSL = combine(this, com.pguardiola.uigesturegen.dsl.doubleTap()) fun doubleTap(): ActionDSL = FreeApplicative.liftF(GesturesDSL.DoubleTap) fun ActionDSL.pinchIn(percent: Int, steps: Int): ActionDSL = combine(this, com.pguardiola.uigesturegen.dsl.pinchIn(percent, steps)) fun pinchIn(percent: Int, steps: Int): ActionDSL = FreeApplicative.liftF(GesturesDSL.PinchOut(percent, steps)) // ... @Guardiola31337

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free dsl @Guardiola31337 Define your algebra (a.k.a. operations) Lift everything to the context of free Provide semantics with the interpreter

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interpreter fun safeInterpreter(view: UiObject): FunctionK>> = object : FunctionK>> { override fun invoke(fa: GesturesDSLKind ): ValidatedKind, A> { // ... return when (g) { is GesturesDSL.Click -> view.click().validate({ GestureError.ClickError(view) }) // ... } as ValidatedKind, A> } } @Guardiola31337

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interpreter fun loggingInterpreter(view: UiObject): FunctionK> = object : FunctionK> { override fun invoke(fa: GesturesDSLKind ): EitherKind { println(fa) return safeInterpreterEither(view) as EitherKind } } @Guardiola31337

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Define your algebra (a.k.a. operations) Lift everything to the context of free Provide semantics with the interpreter Execute the AST using the interpreter free dsl @Guardiola31337

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unfold fun ActionDSL .validate(view: UiObject): ValidatedNel = Try { this.foldMap( safeInterpreter(view), Validated.applicative>()).ev() }.fold({ GestureError.UnknownError(it).invalidNel() }, { it }) @Guardiola31337

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unfold fun ValidatedNel.hasCompletedCorrectly(): Boolean = this.isValid fun ValidatedNel.errors(): List = this.fold({ it.all }, { emptyList() }) @Guardiola31337

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unfold fun ValidatedNel.hasCompletedCorrectly(): Boolean = this.isValid fun ValidatedNel.errors(): List = this.fold({ it.all }, { emptyList() }) @Guardiola31337

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usage private fun composingWithPlus(element: UiObject, pointers: List>): Boolean { val actions = pinchOut(75, 30) + swipeDown(30) + multiTouch(pointers) return actions.failFast(element).hasCompletedCorrectly() } @Guardiola31337

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@Guardiola31337

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takeaways @Guardiola31337

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takeaways @Guardiola31337 Composable

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takeaways @Guardiola31337 Composable Extensible

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takeaways @Guardiola31337 Composable Extensible Reusable using different interpreters

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Composable Extensible Reusable using different interpreters Integration w/ your current stack takeaways @Guardiola31337

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thank you! PABLO GUARDIOLA

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questions? PABLO GUARDIOLA

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we’re hiring! mapbox.com/jobs PABLO GUARDIOLA

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kategory.io https://github.com/Guardiola31337/uiagesturegen https://github.com/Kotlin/KEEP/pull/87 https://github.com/JorgeCastilloPrz/KotlinAndroidFunctional Domain-Specific Languages. Martin Fowler. Special shout out to Raúl Raja, Paco Estévez and Jorge Castillo references @Guardiola31337