diff --git a/kotlin-libraries/pom.xml b/kotlin-libraries/pom.xml index c5b7fed951..92a643e458 100644 --- a/kotlin-libraries/pom.xml +++ b/kotlin-libraries/pom.xml @@ -87,6 +87,13 @@ h2 ${h2database.version} + + + io.arrow-kt + arrow-core + 0.7.3 + + diff --git a/kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithEither.kt b/kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithEither.kt new file mode 100644 index 0000000000..75dfb9a2a4 --- /dev/null +++ b/kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithEither.kt @@ -0,0 +1,54 @@ +package com.baeldung.kotlin.arrow + +import arrow.core.Either +import arrow.core.filterOrElse +import kotlin.math.sqrt + +class FunctionalErrorHandlingWithEither { + + sealed class ComputeProblem { + object OddNumber : ComputeProblem() + object NotANumber : ComputeProblem() + } + + fun parseInput(s : String) : Either = Either.cond(s.toIntOrNull() != null, {-> s.toInt()}, {->ComputeProblem.NotANumber} ) + + fun isEven(x : Int) : Boolean = x % 2 == 0 + + fun biggestDivisor(x: Int) : Int = biggestDivisor(x, 2) + + fun biggestDivisor(x : Int, y : Int) : Int { + if(x == y){ + return 1; + } + if(x % y == 0){ + return x / y; + } + return biggestDivisor(x, y+1) + } + + fun isSquareNumber(x : Int) : Boolean { + val sqrt: Double = sqrt(x.toDouble()) + return sqrt % 1.0 == 0.0 + } + + fun computeWithEither(input : String) : Either { + return parseInput(input) + .filterOrElse(::isEven) {->ComputeProblem.OddNumber} + .map (::biggestDivisor) + .map (::isSquareNumber) + } + + fun computeWithEitherClient(input : String) { + val computeWithEither = computeWithEither(input) + + when(computeWithEither){ + is Either.Right -> "The greatest divisor is square number: ${computeWithEither.b}" + is Either.Left -> when(computeWithEither.a){ + is ComputeProblem.NotANumber -> "Wrong input! Not a number!" + is ComputeProblem.OddNumber -> "It is an odd number!" + } + } + } + +} \ No newline at end of file diff --git a/kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithOption.kt b/kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithOption.kt new file mode 100644 index 0000000000..5fddd1d88e --- /dev/null +++ b/kotlin-libraries/src/main/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithOption.kt @@ -0,0 +1,46 @@ +package com.baeldung.kotlin.arrow + +import arrow.core.None +import arrow.core.Option +import arrow.core.Some +import kotlin.math.sqrt + +class FunctionalErrorHandlingWithOption { + + fun parseInput(s : String) : Option = Option.fromNullable(s.toIntOrNull()) + + fun isEven(x : Int) : Boolean = x % 2 == 0 + + fun biggestDivisor(x: Int) : Int = biggestDivisor(x, 2) + + fun biggestDivisor(x : Int, y : Int) : Int { + if(x == y){ + return 1; + } + if(x % y == 0){ + return x / y; + } + return biggestDivisor(x, y+1) + } + + fun isSquareNumber(x : Int) : Boolean { + val sqrt: Double = sqrt(x.toDouble()) + return sqrt % 1.0 == 0.0 + } + + fun computeWithOption(input : String) : Option { + return parseInput(input) + .filter(::isEven) + .map(::biggestDivisor) + .map(::isSquareNumber) + } + + fun computeWithOptionClient(input : String) : String{ + val computeOption = computeWithOption(input) + + return when(computeOption){ + is None -> "Not an even number!" + is Some -> "The greatest divisor is square number: ${computeOption.t}" + } + } +} \ No newline at end of file diff --git a/kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalDataTypes.kt b/kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalDataTypes.kt new file mode 100644 index 0000000000..692425ee07 --- /dev/null +++ b/kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalDataTypes.kt @@ -0,0 +1,143 @@ +package com.baeldung.kotlin.arrow + +import arrow.core.* +import org.junit.Assert +import org.junit.Test + +class FunctionalDataTypes { + + @Test + fun whenIdCreated_thanValueIsPresent(){ + val id = Id("foo") + val justId = Id.just("foo"); + + Assert.assertEquals("foo", id.extract()) + Assert.assertEquals(justId, id) + } + + fun length(s : String) : Int = s.length + + fun isBigEnough(i : Int) : Boolean = i > 10 + + @Test + fun whenIdCreated_thanMapIsAssociative(){ + val foo = Id("foo") + + val map1 = foo.map(::length) + .map(::isBigEnough) + val map2 = foo.map { s -> isBigEnough(length(s)) } + + Assert.assertEquals(map1, map2) + } + + fun lengthId(s : String) : Id = Id.just(length(s)) + + fun isBigEnoughId(i : Int) : Id = Id.just(isBigEnough(i)) + + @Test + fun whenIdCreated_thanFlatMapIsAssociative(){ + val bar = Id("bar") + + val flatMap = bar.flatMap(::lengthId) + .flatMap(::isBigEnoughId) + val flatMap1 = bar.flatMap { s -> lengthId(s).flatMap(::isBigEnoughId) } + + Assert.assertEquals(flatMap, flatMap1) + } + + @Test + fun whenOptionCreated_thanValueIsPresent(){ + val factory = Option.just(42) + val constructor = Option(42) + val emptyOptional = Option.empty() + val fromNullable = Option.fromNullable(null) + + Assert.assertEquals(42, factory.getOrElse { -1 }) + Assert.assertEquals(factory, constructor) + Assert.assertEquals(emptyOptional, fromNullable) + } + + @Test + fun whenOptionCreated_thanConstructorDifferFromFactory(){ + val constructor : Option = Option(null) + val fromNullable : Option = Option.fromNullable(null) + + try{ + constructor.map { s -> s!!.length } + Assert.fail() + } catch (e : KotlinNullPointerException){ + fromNullable.map { s->s!!.length } + } + Assert.assertNotEquals(constructor, fromNullable) + } + + fun wrapper(x : Integer?) : Option = if (x == null) Option.just(-1) else Option.just(x.toInt()) + + @Test + fun whenOptionFromNullableCreated_thanItBreaksLeftIdentity(){ + val optionFromNull = Option.fromNullable(null) + + Assert.assertNotEquals(optionFromNull.flatMap(::wrapper), wrapper(null)) + } + + @Test + fun whenEitherCreated_thanOneValueIsPresent(){ + val rightOnly : Either = Either.right(42) + val leftOnly : Either = Either.left("foo") + + Assert.assertTrue(rightOnly.isRight()) + Assert.assertTrue(leftOnly.isLeft()) + Assert.assertEquals(42, rightOnly.getOrElse { -1 }) + Assert.assertEquals(-1, leftOnly.getOrElse { -1 }) + + Assert.assertEquals(0, rightOnly.map { it % 2 }.getOrElse { -1 }) + Assert.assertEquals(-1, leftOnly.map { it % 2 }.getOrElse { -1 }) + Assert.assertTrue(rightOnly.flatMap { Either.Right(it % 2) }.isRight()) + Assert.assertTrue(leftOnly.flatMap { Either.Right(it % 2) }.isLeft()) + } + + @Test + fun whenEvalNowUsed_thenMapEvaluatedLazily(){ + val now = Eval.now(1) + Assert.assertEquals(1, now.value()) + + var counter : Int = 0 + val map = now.map { x -> counter++; x+1 } + Assert.assertEquals(0, counter) + + val value = map.value() + Assert.assertEquals(2, value) + Assert.assertEquals(1, counter) + } + + @Test + fun whenEvalLaterUsed_theResultIsMemoized(){ + var counter : Int = 0 + val later = Eval.later { counter++; counter } + Assert.assertEquals(0, counter) + + val firstValue = later.value() + Assert.assertEquals(1, firstValue) + Assert.assertEquals(1, counter) + + val secondValue = later.value() + Assert.assertEquals(1, secondValue) + Assert.assertEquals(1, counter) + } + + @Test + fun whenEvalAlwaysUsed_theResultIsNotMemoized(){ + var counter : Int = 0 + val later = Eval.always { counter++; counter } + Assert.assertEquals(0, counter) + + val firstValue = later.value() + Assert.assertEquals(1, firstValue) + Assert.assertEquals(1, counter) + + val secondValue = later.value() + Assert.assertEquals(2, secondValue) + Assert.assertEquals(2, counter) + } + +} \ No newline at end of file diff --git a/kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithEitherTest.kt b/kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithEitherTest.kt new file mode 100644 index 0000000000..47fbf825a0 --- /dev/null +++ b/kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithEitherTest.kt @@ -0,0 +1,68 @@ +package com.baeldung.kotlin.arrow + +import arrow.core.Either +import com.baeldung.kotlin.arrow.FunctionalErrorHandlingWithEither.ComputeProblem.NotANumber +import com.baeldung.kotlin.arrow.FunctionalErrorHandlingWithEither.ComputeProblem.OddNumber +import org.junit.Assert +import org.junit.Test + +class FunctionalErrorHandlingWithEitherTest { + + val operator = FunctionalErrorHandlingWithEither() + + @Test + fun givenInvalidInput_whenComputeInvoked_NotANumberIsPresent(){ + val computeWithEither = operator.computeWithEither("bar") + + Assert.assertTrue(computeWithEither.isLeft()) + when(computeWithEither){ + is Either.Left -> when(computeWithEither.a){ + NotANumber -> "Ok." + else -> Assert.fail() + } + else -> Assert.fail() + } + } + + @Test + fun givenOddNumberInput_whenComputeInvoked_OddNumberIsPresent(){ + val computeWithEither = operator.computeWithEither("121") + + Assert.assertTrue(computeWithEither.isLeft()) + when(computeWithEither){ + is Either.Left -> when(computeWithEither.a){ + OddNumber -> "Ok." + else -> Assert.fail() + } + else -> Assert.fail() + } + } + + @Test + fun givenEvenNumberWithoutSquare_whenComputeInvoked_OddNumberIsPresent(){ + val computeWithEither = operator.computeWithEither("100") + + Assert.assertTrue(computeWithEither.isRight()) + when(computeWithEither){ + is Either.Right -> when(computeWithEither.b){ + false -> "Ok." + else -> Assert.fail() + } + else -> Assert.fail() + } + } + + @Test + fun givenEvenNumberWithSquare_whenComputeInvoked_OddNumberIsPresent(){ + val computeWithEither = operator.computeWithEither("98") + + Assert.assertTrue(computeWithEither.isRight()) + when(computeWithEither){ + is Either.Right -> when(computeWithEither.b){ + true -> "Ok." + else -> Assert.fail() + } + else -> Assert.fail() + } + } +} \ No newline at end of file diff --git a/kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithOptionTest.kt b/kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithOptionTest.kt new file mode 100644 index 0000000000..3ca4cd033f --- /dev/null +++ b/kotlin-libraries/src/test/kotlin/com/baeldung/kotlin/arrow/FunctionalErrorHandlingWithOptionTest.kt @@ -0,0 +1,34 @@ +package com.baeldung.kotlin.arrow + +import org.junit.Assert +import org.junit.Test + +class FunctionalErrorHandlingWithOptionTest { + + val operator = FunctionalErrorHandlingWithOption() + + @Test + fun givenInvalidInput_thenErrorMessageIsPresent(){ + val useComputeOption = operator.computeWithOptionClient("foo") + Assert.assertEquals("Not an even number!", useComputeOption) + } + + @Test + fun givenOddNumberInput_thenErrorMessageIsPresent(){ + val useComputeOption = operator.computeWithOptionClient("539") + Assert.assertEquals("Not an even number!",useComputeOption) + } + + @Test + fun givenEvenNumberInputWithNonSquareNum_thenFalseMessageIsPresent(){ + val useComputeOption = operator.computeWithOptionClient("100") + Assert.assertEquals("The greatest divisor is square number: false",useComputeOption) + } + + @Test + fun givenEvenNumberInputWithSquareNum_thenTrueMessageIsPresent(){ + val useComputeOption = operator.computeWithOptionClient("242") + Assert.assertEquals("The greatest divisor is square number: true",useComputeOption) + } + +} \ No newline at end of file