com.salesforce.op.aggregators.ExtendedMultiset.scala Maven / Gradle / Ivy

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/*
 * Copyright (c) 2017, Salesforce.com, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * * Neither the name of the copyright holder nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package com.salesforce.op.aggregators

import com.twitter.algebird._

/**
 * Multiset with possible negative counters (so what)
 *
 * Multiset - is a generalization of the concept of a set that,
 * unlike a set, allows multiple instances of the multiset's elements.
 * For example, {a, a, b} and {a, b} are different multisets although they are the same set.
 * However, order does not matter, so {a, a, b} and {a, b, a} are the same multiset.
 */
trait ExtendedMultiset extends MapMonoid[String, Long] with Group[Map[String, Long]] {
  override def negate(kv: Map[String, Long]): Map[String, Long] = kv.map { case (k, v) => k -> -v }

  override def minus(x: Map[String, Long], y: Map[String, Long]): Map[String, Long] = {
    val keys = x.keySet ++ y.keySet
    val kvPairs = keys map (k => k -> (x.getOrElse(k, 0L) - y.getOrElse(k, 0L))) filter (_._2 != 0L)
    kvPairs.toMap
  }
}

object ExtendedMultiset extends ExtendedMultiset