我如何移植Iterables.filter(tree? ? ? ? ? ? ? ? // do the first search using the bounds? ? ? ? ? ? ? ? .search(bounds),? ? ? ? ? ? ? ? // refine using the exact distance? ? ? ? ? ? ? ? entry -> {? ? ? ? ? ? ? ? ? ? Point p = entry.geometry();? ? ? ? ? ? ? ? ? ? Position position = Position.create(p.y(), p.x());? ? ? ? ? ? ? ? ? ? return from.getDistanceToKm(position) < distanceKm;? ? ? ? ? ? ? ? });從 Java 到 Scala？我的以下方法失敗了：import com.github.davidmoten.grumpy.core.Positionimport com.github.davidmoten.rtree2.{Iterables, RTree}import com.github.davidmoten.rtree2.geometry.{Geometries, Point}val sydney = Geometries.point(151.2094, -33.86)val canberra = Geometries.point(149.1244, -35.3075)val brisbane = Geometries.point(153.0278, -27.4679)val bungendore = Geometries.point(149.4500, -35.2500)var tree = RTree.star.create[String, Point]tree = tree.add("Sydney", sydney)tree = tree.add("Brisbane", brisbane)val distanceKm = 300val list = Iterables.toList(search(tree, canberra, distanceKm))def createBounds(from: Position, distanceKm: Double) = { // this calculates a pretty accurate bounding box. Depending on the? // performance you require you wouldn't have to be this accurate because? // accuracy is enforced later? val north = from.predict(distanceKm, 0)? val south = from.predict(distanceKm, 180)? val east = from.predict(distanceKm, 90)? val west = from.predict(distanceKm, 270)? Geometries.rectangle(west.getLon, south.getLat, east.getLon, north.getLat)}因為類型entry似乎沒有明確定義。
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tree類型RTree[String, Point]為T=String, S=Point. 所以tree.search(bounds)有 type Iterable[Entry[String, Point]]。所以entry有 type Entry[String, Point]。
嘗試
(entry: Entry[String,Point]) => {
def foo(entry: Entry[String,Point]) = {
val p = entry.geometry
val position = Position.create(p.y, p.x)
from.getDistanceToKm(position) < distanceKm
}
foo(entry)
})
在 Scala 2.13.0、rtree2 0.9-RC1、grumpy-core 0.2.4 中測試。
在 2.11 中，這應該只是
import scala.compat.java8.FunctionConverters._
((entry: Entry[String,Point]) => {
def foo(entry: Entry[String,Point]) = {
val p = entry.geometry
val position = Position.create(p.y, p.x)
from.getDistanceToKm(position) < distanceKm
}
foo(entry)
}).asJava
libraryDependencies += "org.scala-lang.modules" %% "scala-java8-compat" % "0.9.0"
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