/*
* 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.jena.sparql.function.library.leviathan;
import java.util.List;
import org.apache.jena.atlas.lib.Lib ;
import org.apache.jena.query.QueryBuildException ;
import org.apache.jena.sparql.expr.ExprEvalException ;
import org.apache.jena.sparql.expr.ExprList ;
import org.apache.jena.sparql.expr.NodeValue ;
import org.apache.jena.sparql.function.FunctionBase ;
public class log extends FunctionBase {
@Override
public NodeValue exec(List<NodeValue> args) {
if (args.size() < 1 || args.size() > 2)
throw new ExprEvalException("Invalid number of arguments");
NodeValue v = args.get(0);
if (args.size() == 1) {
// Log base 10
return NodeValue.makeDouble(Math.log10(v.getDouble()));
} else {
// Log with arbitrary base
// See http://en.wikipedia.org/wiki/List_of_logarithmic_identities#Changing_the_base
NodeValue base = args.get(1);
return NodeValue.makeDouble(Math.log10(v.getDouble()) / Math.log10(base.getDouble()));
}
}
@Override
public void checkBuild(String uri, ExprList args) {
if (args.size() < 1 || args.size() > 2)
throw new QueryBuildException("Function '" + Lib.className(this) + "' takes one/two argument(s)");
}
}