Denis.Zharkov
32 lines
704 B
Kotlin
Vendored
32 lines
704 B
Kotlin
Vendored
// !LANGUAGE: +ContextReceivers
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// TARGET_BACKEND: JVM_IR
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// WITH_STDLIB
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interface Semigroup<T> {
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infix fun T.combine(other: T): T
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}
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interface Monoid<T> : Semigroup<T> {
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val unit: T
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}
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object IntMonoid : Monoid<Int> {
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override fun Int.combine(other: Int): Int = this + other
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override val unit: Int = 0
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}
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object StringMonoid : Monoid<String> {
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override fun String.combine(other: String): String = this + other
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override val unit: String = ""
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}
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context(Monoid<T>)
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fun <T> List<T>.sum(): T = fold(unit) { acc, e -> acc.combine(e) }
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fun box(): String {
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with(IntMonoid) {
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listOf(1, 2, 3).sum()
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}
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return with(StringMonoid) {
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listOf("O", "K").sum()
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}
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}
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