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• CollectionUtil.kt

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org.jetbrains.kotlin.backend.common.CollectionUtil.kt Maven / Gradle / Ivy

/*
 * Copyright 2000-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
 * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
 */

package org.jetbrains.kotlin.backend.common

fun  Collection.atMostOne(): T? {
    return when (this.size) {
        0 -> null
        1 -> this.iterator().next()
        else -> throw IllegalArgumentException("Collection has more than one element.")
    }
}

inline fun  Iterable.atMostOne(predicate: (T) -> Boolean): T? = this.filter(predicate).atMostOne()