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Functional Programming with Arrow in Kotlin @ragunathjawahar • Obvious (previously, Uncommon Bangalore)

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, key: Char): Index { for (i in array.indices) { if (array[i] == key) return i } return -1 } typealias Index = Int

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fun findFirst(array: Array, key: Char): Index { for (i in array.indices) { if (array[i] == key) return i } return -1 } typealias Index = Int

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fun findFirst(array: Array, key: Char): Index { for (i in array.indices) { if (array[i] == key) return i } return -1 } typealias Index = Int

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fun findFirst(array: Array, key: Char): Index { for (i in array.indices) { if (array[i] == key) return i } return -1 } typealias Index = Int // findFirst(chars, ‘e’) != -1

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fun findFirst(array: Array, key: Char): Index { for (i in array.indices) { if (array[i] == key) return i } return -1 } typealias Index = Int // findFirst(chars, ‘e’) != -1

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fun findFirst(array: Array, key: Char): Index { for (i in array.indices) { if (array[i] == key) return i } return -1 } typealias Index = Int

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fun findFirst(array: Array, key: Char): Index? { for (i in array.indices) { if (array[i] == key) return i } return null } typealias Index = Int

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fun findFirst(array: Array, key: Char): Option { for (i in array.indices) { if (array[i] == key) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, key: Char): Option { for (i in array.indices) { if (array[i] == key) return Some(i) } return None } typealias Index = Int // absence // presence

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fun findFirst(array: Array, key: Char): Option { for (i in array.indices) { if (array[i] == key) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, key: Char): Option { for (i in array.indices) { if (array[i] == key) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, key: Char): Option { for (i in array.indices) { if (array[i] == key) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, key: A): Option { for (i in array.indices) { if (array[i] == key) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, key: A): Option { for (i in array.indices) { if (array[i] == key) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, key: A): Option { for (i in array.indices) { if (array[i] == key) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, p: (A) -> Boolean): Option { for (i in array.indices) { if (p(array[i])) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, p: (A) -> Boolean): Option { for (i in array.indices) { if (p(array[i])) return Some(i) } return None } typealias Index = Int // findFirst(people, { it.firstName == “Ajay” })

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fun findFirst(array: Array, p: (A) -> Boolean): Option { for (i in array.indices) { if (p(array[i])) return Some(i) } return None } typealias Index = Int // findFirst(people) { it.firstName == “Ajay” }

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fun findFirst(array: Array, p: (A) -> Boolean): Option { for (i in array.indices) { if (p(array[i])) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, p: (A) -> Boolean): Option { for (i in array.indices) { if (p(array[i])) return Some(i) } return None } typealias Index = Int

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fun findFirst(array: Array, p: (A) -> Boolean): Option { for (i in array.indices) { if (p(array[i])) return Some(i) } return None } typealias Index = Int // findFirst(people) { it.firstName == “Ajay” }

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fun Array.findFirst(p:,(A) -> Boolean): Option { for (i in this.indices) { if (p(this[i])) return Some(i) } return None } typealias Index = Int // people.findFirst { it.firstName == “Ajay” }

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fun Array.findFirst(p:,(A) -> Boolean): Option { for (i in this.indices) { if (p(this[i])) return Some(i) } return None } typealias Index = Int

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fun Array.findFirst(p:,(A) -> Boolean): Option { for (i in this.indices) { if (p(this[i])) return Some(i) } return None } fun findFirst(array: Array, key: Char): Int { for (i in array.indices) { if (array[i] == key) return i } return -1 }

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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fun findFirst(array: Array, p:,(A) -> Boolean): Option { tailrec fun go(array: Array, index: Index): Option { return when { index == array.size -> None p(array[index]) -> Some(index) else -> go(array, index + 1) } } return go(array, 0) } But!

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Core Ideas

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Core Ideas • Purity • Referential Transparency • Immutability • Lazy Evaluation

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Notations

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b } // (a: Int, b: Int) -> Int

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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fun add(a: Int, b: Int): Int = a + b val addRef: (Int, Int) -> Int = ::add val subtractLambda = { a: Int, b: Int -> a - b }

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val addRef: (Int, Int) -> Int = ::add addRef.invoke(4, 5) addRef(4, 5)

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Arrow Syntax compile "io.arrow-kt:arrow-syntax:$arrow_version"

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition // bold(“Hello”)

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition // Hello

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition // italic(“Hello”)

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition // Hello

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition // boldItalic(“Hello”)

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition // Hello

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition // italicBold(“Hello”)

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition // Hello

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val bold: (String) -> String = { "$it" } val italic: (String) -> String = { "$it" } val boldItalic = bold compose italic val italicBold = bold forwardCompose italic Composition

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application // x2(10)

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application // 20

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application // x5(10)

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application // 50

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fun multiply(a: Int, b: Int): Int = a * b val x2: (Int) -> Int = ::multiply.partially1(2) val x5: (Int) -> Int = ::multiply.partially1(5) Partial Application

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog } // findCat(animals)

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog } // findDog(animals)

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Reverse fun findFirst( animals: List, predicate: (Animal) -> Boolean ): Option { /* … */ } val findCat: (List) -> Option = ::findFirst.reverse().partially1 { it is Cat } val findDog: (List) -> Option = ::findFirst.reverse().partially1 { it is Dog }

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Logical Complement val onlyCats: (Animal) -> Boolean = { it is Cat } val allCats = filter(animals, onlyCats) val noCats = onlyCats.complement() val allExceptCats = filter(animals, noCats)

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Logical Complement val onlyCats: (Animal) -> Boolean = { it is Cat } val allCats = filter(animals, onlyCats) val noCats = onlyCats.complement() val allExceptCats = filter(animals, noCats)

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Logical Complement val onlyCats: (Animal) -> Boolean = { it is Cat } val allCats = filter(animals, onlyCats) val noCats = onlyCats.complement() val allExceptCats = filter(animals, noCats)

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Logical Complement val onlyCats: (Animal) -> Boolean = { it is Cat } val allCats = filter(animals, onlyCats) val noCats = onlyCats.complement() val allExceptCats = filter(animals, noCats)

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Logical Complement val onlyCats: (Animal) -> Boolean = { it is Cat } val allCats = filter(animals, onlyCats) val noCats = onlyCats.complement() val allExceptCats = filter(animals, noCats)

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Logical Complement val onlyCats: (Animal) -> Boolean = { it is Cat } val allCats = filter(animals, onlyCats) val noCats = onlyCats.complement() val allExceptCats = filter(animals, noCats)

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Logical Complement val onlyCats: (Animal) -> Boolean = { it is Cat } val allCats = filter(animals, onlyCats) val noCats = onlyCats.complement() val allExceptCats = filter(animals, noCats)

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Logical Complement val onlyCats: (Animal) -> Boolean = { it is Cat } val allCats = filter(animals, onlyCats) val noCats = onlyCats.complement() val allExceptCats = filter(animals, noCats)

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Logical Complement val onlyCats: (Animal) -> Boolean = { it is Cat } val allCats = filter(animals, onlyCats) val noCats = onlyCats.complement() val allExceptCats = filter(animals, noCats)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1) // 100

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1) // 100

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Currying (1/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length volume(10, 10, 1) val curriedVolume: (width: Int) -> (height: Int) -> (length: Int) -> Int = ::volume.curried() curriedVolume(10)(10)(1)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10) // (width, height, length)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10) // (length, height, width)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10) // (length) -> (height) -> (width)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10) // (height) -> (width)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10) // (height, width)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10) // (width, height)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10)

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10) // 100

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Currying (2/2) fun volume(width: Int, height: Int, length: Int): Int = width * height * length val area = ::volume .reverse().curried()(1) .uncurried().reverse() area(10, 10)

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More… • memoize() // FunctionN • firstOption() // Array, Sequence, and Iterable • flatten() - tail() - prependTo(List) // List • plus(C) // TupleN • paired() - tripled() // FunctionN • pipe() // FunctionN

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Data Types compile “io.arrow-kt:arrow-core-data:$arrow_version”

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Data Types • Option • Either • Try • Validated • Eval

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Option sealed class Option { object None : Option() data class Some(val t: T) : Option() } Option is an Algebraic Data Type that is used to model the absence of value. In Kotlin they are encoded with sealed class hierarchies.

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Option sealed class Option { object None : Option() data class Some(val t: T) : Option() } Option is an Algebraic Data Type that is used to model the absence of value. In Kotlin they are encoded with sealed class hierarchies.

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Option sealed class Option { object None : Option() data class Some(val t: T) : Option() } Option is an Algebraic Data Type that is used to model the absence of value. In Kotlin they are encoded with sealed class hierarchies.

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Option sealed class Option { object None : Option() data class Some(val t: T) : Option() } Option is an Algebraic Data Type that is used to model the absence of value. In Kotlin they are encoded with sealed class hierarchies.

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Option sealed class Option { object None : Option() data class Some(val t: T) : Option() } Option is an Algebraic Data Type that is used to model the absence of value. In Kotlin they are encoded with sealed class hierarchies.

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Option (Construction) val intOption: Option = Option(1) val intOption: Option = None val intOption: Option = Option.fromNullable(a) // a: Int? val intOption: Option = 1.some() val intOption: Option = none()

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Option (Construction) val intOption: Option = Option(1) val intOption: Option = None val intOption: Option = Option.fromNullable(a) // a: Int? val intOption: Option = 1.some() val intOption: Option = none()

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Option (Construction) val intOption: Option = Option(1) val intOption: Option = None val intOption: Option = Option.fromNullable(a) // a: Int? val intOption: Option = 1.some() val intOption: Option = none()

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Option (Construction) val intOption: Option = Option(1) val intOption: Option = None val intOption: Option = Option.fromNullable(a) // a: Int? val intOption: Option = 1.some() val intOption: Option = none()

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Option (Construction) val intOption: Option = Option(1) val intOption: Option = None val intOption: Option = Option.fromNullable(a) // a: Int? val intOption: Option = 1.some() val intOption: Option = none()

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Option (Construction) val intOption: Option = Option(1) val intOption: Option = None val intOption: Option = Option.fromNullable(a) // a: Int? val intOption: Option = 1.some() val intOption: Option = none()

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Option (Construction) val intOption: Option = Option(1) val intOption: Option = None val intOption: Option = Option.fromNullable(a) // a: Int? val intOption: Option = 1.some() val intOption: Option = none()

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Option (Extraction) val intOption: Option = Option(1) val nullableResult: Int? = intOption.orNull() val result: Int = intOption.getOrElse { 0 }

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Option (Extraction) val intOption: Option = Option(1) val nullableResult: Int? = intOption.orNull() val result: Int = intOption.getOrElse { 0 }

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Option (Extraction) val intOption: Option = Option(1) val nullableResult: Int? = intOption.orNull() val result: Int = intOption.getOrElse { 0 }

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Option (Extraction) val intOption: Option = Option(1) val nullableResult: Int? = intOption.orNull() val result: Int = intOption.getOrElse { 0 }

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Option (Extraction) val intOption: Option = Option(1) val nullableResult: Int? = intOption.orNull() val result: Int = intOption.getOrElse { 0 }

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Option (Extraction - when) val intOption: Option = Option(1) when (intOption) { is None -> 0 is Some -> intOption.t } // Some(1)

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Option (Extraction - when) val intOption: Option = Option(1) when (intOption) { is None -> 0 is Some -> intOption.t } // Some(1)

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Option (Extraction - when) val intOption: Option = Option(1) when (intOption) { is None -> 0 is Some -> intOption.t } // Some(1)

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Option (Extraction - when) val intOption: Option = Option(1) when (intOption) { is None -> 0 is Some -> intOption.t } // Some(1)

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Option (Extraction - when) val intOption: Option = Option(1) when (intOption) { is None -> 0 is Some -> intOption.t } // Some(1)

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Option (Extraction - when) val intOption: Option = Option(1) when (intOption) { is None -> 0 is Some -> intOption.t } // Some(1)

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Option (Extraction - when) val intOption: Option = Option(1) when (intOption) { is None -> 0 is Some -> intOption.t } // Some(1)

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Option (Extraction - fold) val intOption: Option = Option(1) intOption.fold( { 0 }, { it + 1 } ) // Some(2)

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Option (Extraction - fold) val intOption: Option = Option(1) intOption.fold( { 0 }, { it + 1 } ) // Some(2)

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Option (Extraction - fold) val intOption: Option = Option(1) intOption.fold( { 0 }, { it + 1 } ) // Some(2)

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Option (Extraction - fold) val intOption: Option = Option(1) intOption.fold( { 0 }, { it + 1 } ) // Some(2)

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Option (Extraction - fold) val intOption: Option = Option(1) intOption.fold( { 0 }, { it + 1 } ) // Some(2)

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Option (Extraction - fold) val intOption: Option = Option(1) intOption.fold( { 0 }, { it + 1 } ) // Some(2)

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Option (Extraction - fold) val intOption: Option = Option(1) intOption.fold( { 0 }, { it + 1 } ) // Some(2)

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Option (map) val intOption: Option = Option(1) intOption.map { it * 2 } // Some(2) val intOption: Option = None intOption.map { it * 2 } // None

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Option (map) val intOption: Option = Option(1) intOption.map { it * 2 } // Some(2) val intOption: Option = None intOption.map { it * 2 } // None

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Option (map) val intOption: Option = Option(1) intOption.map { it * 2 } // Some(2) val intOption: Option = None intOption.map { it * 2 } // None

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Option (map) val intOption: Option = Option(1) intOption.map { it * 2 } // Some(2) val intOption: Option = None intOption.map { it * 2 } // None

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Option (map) val intOption: Option = Option(1) intOption.map { it * 2 } // Some(2) val intOption: Option = None intOption.map { it * 2 } // None

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Option (map) val intOption: Option = Option(1) intOption.map { it * 2 } // Some(2) val intOption: Option = None intOption.map { it * 2 } // None

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Option (map) val intOption: Option = Option(1) intOption.map { it * 2 } // Some(2) val intOption: Option = None intOption.map { it * 2 } // None

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Option (map) val intOption: Option = Option(1) intOption.map { it * 2 } // Some(2) val intOption: Option = None intOption.map { it * 2 } // None

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = Option(2) oneOption.flatMap { one -> twoOption.map { two -> one + two } } // Some(3)

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = Option(2) oneOption.flatMap { one -> twoOption.map { two -> one + two } } // Some(3)

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = Option(2) oneOption.flatMap { one -> twoOption.map { two -> one + two } } // Some(3)

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = Option(2) oneOption.flatMap { one -> twoOption.map { two -> one + two } } // Some(3)

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = Option(2) oneOption.flatMap { one -> twoOption.map { two -> one + two } } // Some(3)

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = Option(2) oneOption.flatMap { one -> twoOption.map { two -> one + two } } // Some(3)

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = Option(2) oneOption.flatMap { one -> twoOption.map { two -> one + two } } // Some(3)

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = None oneOption.flatMap { one -> twoOption.map { two -> one + two } } // None

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = None oneOption.flatMap { one -> twoOption.map { two -> one + two } } // None

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Option (flatMap) val oneOption: Option = Option(1) val twoOption: Option = None oneOption.flatMap { one -> twoOption.map { two -> one + two } } // None

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = Option(2) Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // Some(3)

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = Option(2) Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // Some(3)

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = Option(2) Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // Some(3)

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = Option(2) Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // Some(3)

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = Option(2) Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // Some(3)

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = Option(2) Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // Some(3)

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = Option(2) Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // Some(3)

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = Option(2) Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // Some(3)

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = Option(2) Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // Some(3)

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = None Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // None

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = None Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // None

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Option (Monad Binding) val oneOption: Option = Option(1) val twoOption: Option = None Option.monad().binding { val one = oneOption.bind() val two = twoOption.bind() one + two }.fix() // None

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = Option(Foam(0.3)) Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // Some(Cappuccino(espresso=Espresso(%=0.3), milk=Milk(%=0.3), // foam=Foam(%=0.3)))

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = None Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // None

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = None Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // None

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Option (Applicative Builder) val maybeEspresso: Option = Option(Espresso(0.3)) val maybeMilkOption: Option = Option(Milk(0.3)) val foamOption: Option = None Option.applicative() .map(maybeEspresso, maybeMilk, maybeFoam) { (espresso, milk, foam) -> Cappuccino(espresso, milk, foam) }.fix() // None

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Either sealed class Either { data class Left(val a: A) : Either() data class Right(val b: B) : Either() } Either is an Algebraic Data Type that is used to model a return type that may return one of two possible values.

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Either sealed class Either { data class Left(val a: A) : Either() data class Right(val b: B) : Either() } Either is an Algebraic Data Type that is used to model a return type that may return one of two possible values.

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Either sealed class Either { data class Left(val a: A) : Either() data class Right(val b: B) : Either() } Either is an Algebraic Data Type that is used to model a return type that may return one of two possible values.

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Either sealed class Either { data class Left(val a: A) : Either() data class Right(val b: B) : Either() } Either is an Algebraic Data Type that is used to model a return type that may return one of two possible values.

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Either sealed class Either { data class Left(val a: A) : Either() data class Right(val b: B) : Either() } Either is an Algebraic Data Type that is used to model a return type that may return one of two possible values.

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Either (Construction) sealed class DomainError { /* ... */ } val result: Either = Right(1) val result: Either = Left(UnknownUser) val result: Either = 1.right() val result: Either = UnknownUser.left()

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Either (Construction) sealed class DomainError { /* ... */ } val result: Either = Right(1) val result: Either = Left(UnknownUser) val result: Either = 1.right() val result: Either = UnknownUser.left()

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Either (Construction) sealed class DomainError { /* ... */ } val result: Either = Right(1) val result: Either = Left(UnknownUser) val result: Either = 1.right() val result: Either = UnknownUser.left()

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Either (Construction) sealed class DomainError { /* ... */ } val result: Either = Right(1) val result: Either = Left(UnknownUser) val result: Either = 1.right() val result: Either = UnknownUser.left()

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Either (Construction) sealed class DomainError { /* ... */ } val result: Either = Right(1) val result: Either = Left(UnknownUser) val result: Either = 1.right() val result: Either = UnknownUser.left()

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Either (Construction) sealed class DomainError { /* ... */ } val result: Either = Right(1) val result: Either = Left(UnknownUser) val result: Either = 1.right() val result: Either = UnknownUser.left()

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Either (Construction) sealed class DomainError { /* ... */ } val result: Either = Right(1) val result: Either = Left(UnknownUser) val result: Either = 1.right() val result: Either = UnknownUser.left()

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Either (Extraction - when) sealed class DomainError { /* ... */ } val result: Either = Right(1) when (result) { is Left -> 0 is Right -> result.b } // Right(1)

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Either (Extraction - when) sealed class DomainError { /* ... */ } val result: Either = Right(1) when (result) { is Left -> 0 is Right -> result.b } // Right(1)

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Either (Extraction - when) sealed class DomainError { /* ... */ } val result: Either = Right(1) when (result) { is Left -> 0 is Right -> result.b } // Right(1)

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Either (Extraction - when) sealed class DomainError { /* ... */ } val result: Either = Right(1) when (result) { is Left -> 0 is Right -> result.b } // Right(1)

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Either (Extraction - when) sealed class DomainError { /* ... */ } val result: Either = Right(1) when (result) { is Left -> 0 is Right -> result.b } // Right(1) F

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Either (Extraction - when) sealed class DomainError { /* ... */ } val result: Either = Right(1) when (result) { is Left -> 0 is Right -> result.b } // Right(1)

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Either (Extraction - when) sealed class DomainError { /* ... */ } val result: Either = Right(1) when (result) { is Left -> 0 is Right -> result.b } // Right(1)

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Either (Extraction - fold) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.fold( { 0 }, { it + 1 } ) // Right(2)

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Either (Extraction - fold) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.fold( { 0 }, { it + 1 } ) // Right(2)

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Either (Extraction - fold) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.fold( { 0 }, { it + 1 } ) // Right(2)

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Either (Extraction - fold) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.fold( { 0 }, { it + 1 } ) // Right(2)

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Either (Extraction - fold) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.fold( { 0 }, { it + 1 } ) // Right(2)

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Either (Extraction - fold) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.fold( { 0 }, { it + 1 } ) // Right(2)

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Either (Extraction - fold) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.fold( { 0 }, { it + 1 } ) // Right(2)

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Either (map) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.map { it * 2 } // Right(2) val result: Either = Left(UnknownUser) result.map { it * 2 } // Left(UnknownUser)

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Either (map) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.map { it * 2 } // Right(2) val result: Either = Left(UnknownUser) result.map { it * 2 } // Left(UnknownUser)

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Either (map) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.map { it * 2 } // Right(2) val result: Either = Left(UnknownUser) result.map { it * 2 } // Left(UnknownUser)

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Either (map) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.map { it * 2 } // Right(2) val result: Either = Left(UnknownUser) result.map { it * 2 } // Left(UnknownUser)

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Either (map) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.map { it * 2 } // Right(2) val result: Either = Left(UnknownUser) result.map { it * 2 } // Left(UnknownUser)

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Either (map) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.map { it * 2 } // Right(2) val result: Either = Left(UnknownUser) result.map { it * 2 } // Left(UnknownUser)

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Either (map) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.map { it * 2 } // Right(2) val result: Either = Left(UnknownUser) result.map { it * 2 } // Left(UnknownUser)

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Either (map) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.map { it * 2 } // Right(2) val result: Either = Left(UnknownUser) result.map { it * 2 } // Left(UnknownUser)

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Either (map) sealed class DomainError { /* ... */ } val result: Either = Right(1) result.map { it * 2 } // Right(2) val result: Either = Left(UnknownUser) result.map { it * 2 } // Left(UnknownUser)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) result1.flatMap { one -> result2.map { two -> one + two } } // Right(3)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) result1.flatMap { one -> result2.map { two -> one + two } } // Right(3)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) result1.flatMap { one -> result2.map { two -> one + two } } // Right(3)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) result1.flatMap { one -> result2.map { two -> one + two } } // Right(3)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) result1.flatMap { one -> result2.map { two -> one + two } } // Right(3)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) result1.flatMap { one -> result2.map { two -> one + two } } // Right(3)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) result1.flatMap { one -> result2.map { two -> one + two } } // Right(3)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Left(UnknownUser) result1.flatMap { one -> result2.map { two -> one + two } } // Left(UnknownUser)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Left(UnknownUser) result1.flatMap { one -> result2.map { two -> one + two } } // Left(UnknownUser)

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Either (flatMap) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Left(UnknownUser) result1.flatMap { one -> result2.map { two -> one + two } } // Left(UnknownUser)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Right(3)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Right(3)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Right(3)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Right(3)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Right(3)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Right(3)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Right(3)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Right(3)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Right(2) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Right(3)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Left(UnknownUser) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Left(UnknownUser)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Left(UnknownUser) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Left(UnknownUser)

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Either (Monad Binding) sealed class DomainError { /* ... */ } val result1: Either = Right(1) val result2: Either = Left(UnknownUser) Either.monad.binding { val one = result1.bind() val two = result2.bind() one + two }.fix() // Left(UnknownUser)

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Right(Water(0.6)) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Right(Americano(espresso=Espresso(%=0.4), water=Water(%=0.6)))

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Left(RefillWater) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Left(RefillWater)

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Left(RefillWater) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Left(RefillWater)

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Either (Applicative Builder) sealed class CoffeeMakerError { /* ... */ } val espressoResult: Either = Right(Espresso(0.4)) val waterResult: Either = Left(RefillWater) Either.applicative() .map(espressoResult, waterResult) { (espresso, water) -> Americano(espresso, water) }.fix() // Left(RefillWater)

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More… • Try // Success - Failure • Validated // Valid - Invalid • Eval // Now - Always - Later - Defer • TupleN // Tuple2 - Tuple22

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Typeclasses compile “io.arrow-kt:arrow-typeclasses:$arrow_version” kapt “io.arrow-kt:arrow-meta:$arrow_version”

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Typeclasses • Polymorphism in functional programming. • Separates data from behaviour. • Maybe governed by algebraic / category theoretic laws. • Implemented as interfaces in Kotlin. • One Typeclass instance per type.

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Typeclasses • Show • Eq • Semigroup • Functor • Monad • …

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Show interface Show { fun A.show(): String } The Show typeclass abstracts the ability to obtain a String representation of any object.

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Show interface Show { fun A.show(): String } The Show typeclass abstracts the ability to obtain a String representation of any object.

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Show interface Show { fun A.show(): String } The Show typeclass abstracts the ability to obtain a String representation of any object.

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Show interface Show { fun A.show(): String } The Show typeclass abstracts the ability to obtain a String representation of any object.

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Eq interface Eq { fun F.eqv(b: F): Boolean fun F.neqv(b: F): Boolean = !eqv(b) } The Eq typeclass abstracts the ability to compare two instances of any object. It can be compared to the typeclass equivalent of Java’s Object#equals.

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Eq interface Eq { fun F.eqv(b: F): Boolean fun F.neqv(b: F): Boolean = !eqv(b) } The Eq typeclass abstracts the ability to compare two instances of any object. It can be compared to the typeclass equivalent of Java’s Object#equals.

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Eq interface Eq { fun F.eqv(b: F): Boolean fun F.neqv(b: F): Boolean = !eqv(b) } The Eq typeclass abstracts the ability to compare two instances of any object. It can be compared to the typeclass equivalent of Java’s Object#equals.

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Eq interface Eq { fun F.eqv(b: F): Boolean fun F.neqv(b: F): Boolean = !eqv(b) } The Eq typeclass abstracts the ability to compare two instances of any object. It can be compared to the typeclass equivalent of Java’s Object#equals.

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Eq interface Eq { fun F.eqv(b: F): Boolean fun F.neqv(b: F): Boolean = !eqv(b) } The Eq typeclass abstracts the ability to compare two instances of any object. It can be compared to the typeclass equivalent of Java’s Object#equals.

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Semigroup interface Semigroup { fun A.combine(b: A): A operator fun A.plus(b: A): A = this.combine(b) } The Semigroup for some given type A has a single operation combine which takes two values of type A, and returns a value of type A. This operation must be associative.

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Semigroup interface Semigroup { fun A.combine(b: A): A operator fun A.plus(b: A): A = this.combine(b) } The Semigroup for some given type A has a single operation combine which takes two values of type A, and returns a value of type A. This operation must be associative.

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Semigroup interface Semigroup { fun A.combine(b: A): A operator fun A.plus(b: A): A = this.combine(b) } The Semigroup for some given type A has a single operation combine which takes two values of type A, and returns a value of type A. This operation must be associative.

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Semigroup interface Semigroup { fun A.combine(b: A): A operator fun A.plus(b: A): A = this.combine(b) } The Semigroup for some given type A has a single operation combine which takes two values of type A, and returns a value of type A. This operation must be associative.

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Semigroup interface Semigroup { fun A.combine(b: A): A operator fun A.plus(b: A): A = this.combine(b) } The Semigroup for some given type A has a single operation combine which takes two values of type A, and returns a value of type A. This operation must be associative.

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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Creating Instances data class Person(val firstName: String, val lastName: String) { companion object } @extension interface PersonShow : Show { override fun Person.show(): String = "$firstName $lastName" } val john = Person("John", "Doe") Person.show().run { john.show() } // John Doe

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More… • Hash • Order • Traverse • Applicative • And many more…

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Optics compile “io.arrow-kt:arrow-optics:$arrow_version” kapt “io.arrow-kt:arrow-meta:$arrow_version”

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Lens @optics data class UserProfile( val name: Name, /* Not shown for brevity */ val contact: Contact ) { companion object } @optics data class Contact( val email: String, val phone: String ) { companion object }

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Without Lens val profile = UserProfile( Name("John", "Doe"), Contact("[email protected]", "6483920164") ) val updatedProfile = profile.copy( contact = profile.contact.copy( email = "[email protected]" ) )

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Without Lens val profile = UserProfile( Name("John", "Doe"), Contact("[email protected]", "6483920164") ) val updatedProfile = profile.copy( contact = profile.contact.copy( email = "[email protected]" ) )

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Without Lens val profile = UserProfile( Name("John", "Doe"), Contact("[email protected]", "6483920164") ) val updatedProfile = profile.copy( contact = profile.contact.copy( email = "[email protected]" ) )

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Without Lens val profile = UserProfile( Name("John", "Doe"), Contact("[email protected]", "6483920164") ) val updatedProfile = profile.copy( contact = profile.contact.copy( email = "[email protected]" ) )

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Without Lens val profile = UserProfile( Name("John", "Doe"), Contact("[email protected]", "6483920164") ) val updatedProfile = profile.copy( contact = profile.contact.copy( email = "[email protected]" ) )

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Without Lens val profile = UserProfile( Name("John", "Doe"), Contact("[email protected]", "6483920164") ) val updatedProfile = profile.copy( contact = profile.contact.copy( email = "[email protected]" ) )

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile) // “[email protected]”

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With Lens val profile = UserProfile( /* … */ ) val emailLens: Lens = UserProfile.contact.email val workEmail = "[email protected]" val updatedProfile = emailLens.modify(profile) { workEmail } val email = emailLens.get(profile)

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Optional @optics data class ShoppingCart( val id: String, val cartItems: ListK ) { companion object } @optics data class CartItem( val product: Product, /* Not shown for brevity */ val quantity: Int ) { companion object }

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Optional @optics data class ShoppingCart( val id: String, val cartItems: ListK ) { companion object } @optics data class CartItem( val product: Product, /* Not shown for brevity */ val quantity: Int ) { companion object }

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Optional @optics data class ShoppingCart( val id: String, val cartItems: ListK ) { companion object } @optics data class CartItem( val product: Product, /* Not shown for brevity */ val quantity: Int ) { companion object }

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Optional @optics data class ShoppingCart( val id: String, val cartItems: ListK ) { companion object } @optics data class CartItem( val product: Product, /* Not shown for brevity */ val quantity: Int ) { companion object }

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Optional @optics data class ShoppingCart( val id: String, val cartItems: ListK ) { companion object } @optics data class CartItem( val product: Product, /* Not shown for brevity */ val quantity: Int ) { companion object }

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Optional @optics data class ShoppingCart( val id: String, val cartItems: ListK ) { companion object } @optics data class CartItem( val product: Product, /* Not shown for brevity */ val quantity: Int ) { companion object }

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Optional @optics data class ShoppingCart( val id: String, val cartItems: ListK ) { companion object } @optics data class CartItem( val product: Product, /* Not shown for brevity */ val quantity: Int ) { companion object }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Set) val shoppingCart = ShoppingCart("CRT19321", cartItems) val quantityOptional: Optional = ShoppingCart .cartItems .index(ListK.index(), productIndex) .quantity val updatedCart = quantityOptional.modify(shoppingCart) { it + 1 }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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Optional (Get) val cartItemOption = ShoppingCart .cartItems .index(ListK.index(), productIndex) .getOption(shoppingCart) val sameCartItemOption = ListK.index().run { ShoppingCart.cartItems[productIndex].getOption(shoppingCart) }

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More… • Iso • Prism • Getter / Setter • Fold • Each • And others …

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That’s not it… • Arrow Fx • Effects • Arrow Query Language • Generic • Integrations • Free • Recursion Schemes

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Resources • https://arrow-kt.io/docs/ • http://learnyouahaskell.com/ • https://caster.io/courses/functional-programming-in-kotlin-with-arrow • https://github.com/hemanth/functional-programming-jargon#function • https://wiki.haskell.org/Typeclassopedia • http://nealford.com/functionalthinking.html • https://prod.packtpub.com/in/application-development/functional-kotlin

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end; @ragunathjawahar Twitter / Medium / GitHub