Zalim Bashorov
49 lines
1.5 KiB
Kotlin
49 lines
1.5 KiB
Kotlin
/*
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* Copyright 2010-2014 JetBrains s.r.o.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package kotlin
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/**
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* Helper method for implementing [[Comparable]] methods using a list of functions
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* to calculate the values to compare
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*/
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public fun <T : Any> compareBy(a: T?, b: T?, vararg functions: T.() -> Comparable<*>?): Int {
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require(functions.size > 0)
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if (a identityEquals b) return 0
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if (a == null) return - 1
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if (b == null) return 1
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for (fn in functions) {
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val v1 = a.fn()
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val v2 = b.fn()
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val diff = compareValues(v1, v2)
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if (diff != 0) return diff
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}
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return 0
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}
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/**
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* Compares the two values which may be [[Comparable]] otherwise
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* they are compared via [[#equals()]] and if they are not the same then
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* the [[#hashCode()]] method is used as the difference
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*/
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public fun <T : Comparable<*>> compareValues(a: T?, b: T?): Int {
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if (a identityEquals b) return 0
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if (a == null) return - 1
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if (b == null) return 1
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return (a as Comparable<Any?>).compareTo(b)
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}
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