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VectorBuilder avoids copying data if possible
When calling VectorBuilder#addAll(Vector), if the builder is currently empty, it will share structure with the argument Vector in order to avoid iterating and copying the entire argument Vector. This is very helpful especially for the Vector#concat implementation, which in most cases will work by creating a new builder, and adding both vectors to the builder.
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test/scalacheck/scala/collection/immutable/VectorBuilderProperties.scala
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| /* | ||
| * Scala (https://www.scala-lang.org) | ||
| * | ||
| * Copyright EPFL and Lightbend, Inc. | ||
| * | ||
| * Licensed under Apache License 2.0 | ||
| * (http://www.apache.org/licenses/LICENSE-2.0). | ||
| * | ||
| * See the NOTICE file distributed with this work for | ||
| * additional information regarding copyright ownership. | ||
| */ | ||
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| package scala.collection.immutable | ||
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| import org.scalacheck.Properties | ||
| import org.scalacheck.Prop._ | ||
| import org.scalacheck._ | ||
| import org.scalacheck.Arbitrary.arbitrary | ||
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| object VectorBuilderProperties extends Properties("VectorBuilder") { | ||
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| type Elem = Int | ||
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| /** Wrapper for all the many parameters to our properties | ||
| * | ||
| * @param a first vector to add | ||
| * @param dropA number of elems to drop from `a` before adding | ||
| * @param dropRightA number of elems to dropRight from `a` before adding | ||
| * @param b second vector to add | ||
| * @param dropB number of elems to drop from `b` before adding | ||
| * @param dropRightB number of elems to dropRight from `b` before adding | ||
| * @param c first vector to add | ||
| * @param dropC number of elems to drop from `c` before adding | ||
| * @param dropRightC number of elems to dropRight from `c` before adding | ||
| */ | ||
| case class AddAllTestCase( | ||
| a: Vector[Elem], | ||
| dropA: Int, | ||
| dropRightA: Int, | ||
| b: Vector[Elem], | ||
| dropB: Int, | ||
| dropRightB: Int, | ||
| c: Vector[Elem], | ||
| dropC: Int, | ||
| dropRightC: Int | ||
| ) | ||
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| implicit val arbAddAllTestCase: Arbitrary[AddAllTestCase] = | ||
| Arbitrary { | ||
| for { | ||
| a <- arbitrary[Vector[Elem]] | ||
| dropA <- Gen.choose(0, 500) | ||
| dropRightA <- Gen.choose(0, 500) | ||
| b <- arbitrary[Vector[Elem]] | ||
| dropB <- Gen.choose(0, 500) | ||
| dropRightB <- Gen.choose(0, 500) | ||
| c <- arbitrary[Vector[Elem]] | ||
| dropC <- Gen.choose(0, 500) | ||
| dropRightC <- Gen.choose(0, 500) | ||
| } yield AddAllTestCase(a, dropA, dropRightA, b, dropB, dropRightB, c, dropC, dropRightC) | ||
| } | ||
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| property("addAll(a).addAll(b).addAll(c).result() == a ++ b ++ c") = | ||
| forAll { testCase: AddAllTestCase => | ||
| val AddAllTestCase(a, dropA, dropRightA, b, dropB, dropRightB, c, dropC, dropRightC) = testCase | ||
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| val actual: Seq[Elem] = | ||
| new VectorBuilder[Elem] | ||
| .addAll(a.drop(dropA).dropRight(dropRightA)) | ||
| .addAll(b.drop(dropB).dropRight(dropRightB)) | ||
| .addAll(c.drop(dropC).dropRight(dropRightC)) | ||
| .result() | ||
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| val expected = | ||
| a.toList.drop(dropA).dropRight(dropRightA) ++ | ||
| b.toList.drop(dropB).dropRight(dropRightB) ++ | ||
| c.toList.drop(dropC).dropRight(dropRightC) | ||
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| actual ?= expected | ||
| } | ||
| property("addAll(a).addAll(b).addAll(c).size == (a ++ b ++ c).size") = | ||
| forAll { testCase: AddAllTestCase => | ||
| val AddAllTestCase(a, dropA, dropRightA, b, dropB, dropRightB, c, dropC, dropRightC) = testCase | ||
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| val actual: Int = | ||
| new VectorBuilder[Elem] | ||
| .addAll(a.drop(dropA).dropRight(dropRightA)) | ||
| .addAll(b.drop(dropB).dropRight(dropRightB)) | ||
| .addAll(c.drop(dropC).dropRight(dropRightC)) | ||
| .size | ||
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| val expected = | ||
| (a.toList.drop(dropA).dropRight(dropRightA) ++ | ||
| b.toList.drop(dropB).dropRight(dropRightB) ++ | ||
| c.toList.drop(dropC).dropRight(dropRightC)).length | ||
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| actual ?= expected | ||
| } | ||
| } |