40 lines
1.6 KiB
Kotlin
40 lines
1.6 KiB
Kotlin
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package io.gitlab.jfronny.scripts
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interface Either<L, R> {
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val isLeft: Boolean
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val isRight: Boolean
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val left: L?
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val right: R?
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fun <U> mapLeft(f: (L) -> U): Either<U, R>
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fun <U> mapRight(f: (R) -> U): Either<L, U>
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fun <U> fold(l: (L) -> U, r: (R) -> U): U
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fun foldLeft(f: (L) -> R): R
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fun foldRight(f: (R) -> L): L
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fun apply(l: (L) -> Unit, r: (R) -> Unit)
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data class Left<L, R>(override val left: L) : Either<L, R> {
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override val isLeft = true
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override val isRight = false
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override val right = null
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override fun <U> mapLeft(f: (L) -> U): Either<U, R> = Left(f(left))
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override fun <U> mapRight(f: (R) -> U): Either<L, U> = Left(left)
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override fun <U> fold(l: (L) -> U, r: (R) -> U): U = l(left)
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override fun foldRight(f: (R) -> L): L = left
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override fun foldLeft(f: (L) -> R): R = f(left)
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override fun apply(l: (L) -> Unit, r: (R) -> Unit) = l(left)
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}
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data class Right<L, R>(override val right: R) : Either<L, R> {
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override val isLeft = false
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override val isRight = true
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override val left = null
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override fun <U> mapLeft(f: (L) -> U): Either<U, R> = Right(right)
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override fun <U> mapRight(f: (R) -> U): Either<L, U> = Right(f(right))
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override fun <U> fold(l: (L) -> U, r: (R) -> U): U = r(right)
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override fun foldRight(f: (R) -> L): L = f(right)
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override fun foldLeft(f: (L) -> R): R = right
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override fun apply(l: (L) -> Unit, r: (R) -> Unit) = r(right)
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}
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}
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fun <T> Either<T, T>.fold(): T = if (isLeft) left!! else right!!
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