/*
* 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.pig.builtin;
import java.io.IOException;
import java.util.List;
import java.util.ArrayList;
import java.math.BigDecimal;
import java.math.RoundingMode;
import org.apache.pig.EvalFunc;
import org.apache.pig.FuncSpec;
import org.apache.pig.data.Tuple;
import org.apache.pig.impl.logicalLayer.schema.Schema;
import org.apache.pig.data.DataType;
import org.apache.pig.impl.logicalLayer.FrontendException;
/**
* ROUND_TO safely rounds a number to a given precision by using an intermediate
* BigDecimal. The too-often seen trick of doing (1000.0 * ROUND(x/1000)) is not
* only hard to read but also fails to produce numerically accurate results.
*
* Given a single data atom and number of digits, it returns a double extending to the
* given number of decimal places.
*
* The result is a multiple of ten to the power given by the digits argument: a
* negative value zeros out correspondingly many places to the left of the
* decimal point: ROUND_TO(0.9876543, 3) is 0.988; ROUND_TO(0.9876543, 0) is
* 1.0; and ROUND_TO(1234.56, -2) is 1200.0.
*
* The optional mode argument specifies the {@link java.math.RoundingMode rounding mode};
* by default, {@link java.math.RoundingMode#HALF_EVEN 'HALF_EVEN'} is used.
*
*/
public class DoubleRoundTo extends EvalFunc<Double>{
/**
* java level API
* @param input expects a numeric value to round, a number of digits to keep, and an optional rounding mode.
* @return output returns a single numeric value, the number with only those digits retained
*/
@Override
public Double exec(Tuple input) throws IOException {
if (input == null || input.size() < 2)
return null;
try {
Double num = (Double)input.get(0);
Integer digits = (Integer)input.get(1);
RoundingMode mode = (input.size() >= 3) ?
RoundingMode.valueOf(DataType.toInteger(input.get(2))) : RoundingMode.HALF_EVEN;
if (num == null) return null;
BigDecimal bdnum = BigDecimal.valueOf(num);
bdnum = bdnum.setScale(digits, mode);
return bdnum.doubleValue();
} catch (Exception e){
throw new IOException("Caught exception processing input row ", e);
}
}
/* (non-Javadoc)
* @see org.apache.pig.EvalFunc#getArgToFuncMapping()
*/
@Override
public List<FuncSpec> getArgToFuncMapping() throws FrontendException {
List<FuncSpec> funcList = new ArrayList<FuncSpec>();
Schema s_dbl_2 = new Schema();
s_dbl_2.add(new Schema.FieldSchema(null, DataType.DOUBLE));
s_dbl_2.add(new Schema.FieldSchema(null, DataType.INTEGER));
Schema s_dbl_3 = new Schema();
s_dbl_3.add(new Schema.FieldSchema(null, DataType.DOUBLE));
s_dbl_3.add(new Schema.FieldSchema(null, DataType.INTEGER));
s_dbl_3.add(new Schema.FieldSchema(null, DataType.INTEGER));
funcList.add(new FuncSpec(this.getClass().getName(), s_dbl_2));
funcList.add(new FuncSpec(this.getClass().getName(), s_dbl_3));
return funcList;
}
@Override
public boolean allowCompileTimeCalculation() {
return true;
}
}