rmuir commented on a change in pull request #299: URL: https://github.com/apache/lucene/pull/299#discussion_r708206903
########## File path: lucene/expressions/src/java/org/apache/lucene/expressions/js/ExpressionMath.java ########## @@ -0,0 +1,44 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.lucene.expressions.js; + +import static org.apache.lucene.util.SloppyMath.haversinMeters; +import static org.apache.lucene.util.SloppyMath.haversinSortKey; + +/** Helper class holding static methods for js math functions */ +public final class ExpressionMath { + + private ExpressionMath() {} + + /** + * Returns the Haversine distance in kilometers between two points specified in decimal degrees + * (latitude/longitude). This works correctly even if the dateline is between the two points. + * + * <p>Error is at most 4E-1 (40cm) from the actual haversine distance, but is typically much + * smaller for reasonable distances: around 1E-5 (0.01mm) for distances less than 1000km. + * + * @param lat1 Latitude of the first point. + * @param lon1 Longitude of the first point. + * @param lat2 Latitude of the second point. + * @param lon2 Longitude of the second point. + * @return distance in kilometers. + */ + public static double haversinKilometers(double lat1, double lon1, double lat2, double lon2) { + return haversinMeters(haversinSortKey(lat1, lon1, lat2, lon2)) / 1000; Review comment: can we add a constant for 1/1000 and multiply by that instead? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
