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Type Refinement with Type Classes and ApplicativeError
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package arrow.refined | |
import arrow.Kind | |
import arrow.core.* | |
import arrow.data.* | |
import arrow.effects.validated.positiveInt.plus | |
import arrow.effects.validated.positiveInt.positive | |
import arrow.extension | |
import arrow.instances.either.applicativeError.applicativeError | |
import arrow.instances.listk.traverse.traverse | |
import arrow.instances.nonemptylist.semigroup.semigroup | |
import arrow.instances.validated.applicativeError.applicativeError | |
import arrow.typeclasses.ApplicativeError | |
import arrow.typeclasses.Traverse | |
/** Arrow refined library */ | |
data class RefinedPredicateException(val msg: String) : IllegalArgumentException(msg) | |
interface Refinement<F, A> { | |
fun applicativeError(): ApplicativeError<F, Nel<RefinedPredicateException>> | |
fun A.refinement(): Boolean | |
fun invalidValueMsg(a: A): String | |
fun refine(value: A): Kind<F, A> = applicativeError().run { | |
value.refinement() | |
.maybe { just(value) } | |
.getOrElse { raiseError(Nel.of(RefinedPredicateException(invalidValueMsg(value)))) } | |
} | |
fun <B> refine(value: A, f: (A) -> B): Kind<F, B> = | |
applicativeError().run { refine(value).map(f) } | |
fun <B> refine2(a: A, b: A, f: (Tuple2<A, A>) -> B): Kind<F, B> = | |
applicativeError().run { | |
map(refine(a), refine(b), f) | |
} | |
fun <B> refine3(a: A, b: A, c: A, f: (Tuple3<A, A, A>) -> B): Kind<F, B> = | |
applicativeError().run { | |
map(refine(a), refine(b), refine(c), f) | |
} | |
fun <B> refine4(a: A, b: A, c: A, d: A, f: (Tuple4<A, A, A, A>) -> B): Kind<F, B> = | |
applicativeError().run { | |
map(refine(a), refine(b), refine(c), refine(d), f) | |
} | |
fun <G, B> refineTraverse(value: Kind<G, A>, traverse: Traverse<G>, f: (A) -> B): Kind<F, Kind<G, B>> = | |
traverse.run { value.traverse(applicativeError()) { refine(it, f) } } | |
fun <B> refineTraverseList(elements: List<A>, f: (A) -> B): Kind<F, List<B>> = | |
applicativeError().run { | |
refineTraverse(elements.k(), ListK.traverse(), f).map { it.fix() } | |
} | |
fun <G> refineSequence(value: Kind<G, A>, traverse: Traverse<G>): Kind<F, Kind<G, A>> = | |
refineTraverse(value, traverse, ::identity) | |
fun refineSequenceList(elements: List<A>): Kind<F, List<A>> = | |
applicativeError().run { | |
refineSequence(elements.k(), ListK.traverse()).map { it.fix() } | |
} | |
} | |
/** Included with Arrow but similar to what a user would define for a custom data type **/ | |
interface PositiveInt<F> : Refinement<F, Int> { | |
override fun Int.refinement(): Boolean = | |
this > 0 | |
override fun invalidValueMsg(a: Int): String = | |
"$a should be > 0" | |
fun Int.positive(): Kind<F, Int> = | |
refine(this) | |
fun <B> Int.positive(f: Int.() -> B): Kind<F, B> = | |
refine(this, f) | |
fun positive(elements: List<Int>): Kind<F, List<Int>> = | |
refineSequenceList(elements) | |
fun <B> positive(elements: List<Int>, f: (Int) -> B): Kind<F, List<B>> = | |
refineTraverseList(elements, f) | |
operator fun Kind<F, Int>.plus(b: Int): Kind<F, Int> = | |
applicativeError().run { map { it + b } } | |
operator fun Kind<F, Int>.plus(b: Kind<F, Int>) = | |
applicativeError().run { map(this@plus, b) { (a, b) -> a + b } } | |
operator fun Int.plus(b: Kind<F, Int>): Kind<F, Int> = | |
applicativeError().run { b.map { this@plus + it } } | |
} | |
/** Error accumulating strategy instance based on `Validated` **/ | |
@extension | |
interface ValidatedPositiveInt : PositiveInt<ValidatedPartialOf<Nel<RefinedPredicateException>>> { | |
override fun applicativeError(): ApplicativeError<ValidatedPartialOf<Nel<RefinedPredicateException>>, Nel<RefinedPredicateException>> = | |
Validated.applicativeError(NonEmptyList.semigroup()) | |
} | |
/** Fail fast strategy instance based on `Either` **/ | |
@extension | |
interface EitherPositiveInt : PositiveInt<EitherPartialOf<Nel<RefinedPredicateException>>> { | |
override fun applicativeError(): ApplicativeError<EitherPartialOf<Nel<RefinedPredicateException>>, Nel<RefinedPredicateException>> = | |
Either.applicativeError() | |
} | |
/** test **/ | |
object test { | |
@JvmStatic | |
fun main(args: Array<String>) { | |
println(0.positive() + 1.positive()) //Valid(1) | |
println(0.positive() + (-1).positive()) //Invalid(e=NonEmptyList(all=[RefinedPredicateException(msg=-1 should be > 0)])) | |
println(positive(listOf(1, 2, 3)) { it * 10 }) //Valid(a=ListK(list=[10, 20, 30])) | |
println(positive(listOf(-1, 2, -3)) { it * 10 }) //Invalid(e=NonEmptyList(all=[RefinedPredicateException(msg=-1 should be >= 0), RefinedPredicateException(msg=-3 should be > 0)])) | |
} | |
} |
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