/**
* Copyright (C) 2009-2013 FoundationDB, LLC
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.foundationdb.server.types.common.funcs;
import com.foundationdb.server.types.LazyList;
import com.foundationdb.server.types.TClass;
import com.foundationdb.server.types.TExecutionContext;
import com.foundationdb.server.types.TOverloadResult;
import com.foundationdb.server.types.value.ValueSource;
import com.foundationdb.server.types.value.ValueTarget;
import com.foundationdb.server.types.texpressions.TInputSetBuilder;
import com.foundationdb.server.types.texpressions.TScalarBase;
import com.foundationdb.server.types.TScalar;
public class TLog extends TScalarBase
{
static final double ln2 = Math.log(2);
public static TScalar[] create(TClass argType)
{
LogType values[] = LogType.values();
TScalar ret[] = new TScalar[values.length];
for (int n = 0; n < ret.length; ++n)
ret[n] = new TLog(values[n], argType);
return ret;
}
static enum LogType
{
LN
{
@Override
double evaluate(double input)
{
return Math.log(input);
}
},
LOG
{
@Override
double evaluate(double input)
{
return Math.log(input);
}
},
LOG10
{
@Override
double evaluate(double input)
{
return Math.log10(input);
}
},
LOG2
{
@Override
double evaluate(double input)
{
return Math.log(input)/ln2;
}
};
abstract double evaluate(double input);
boolean isValid(double input)
{
return input > 0;
}
}
private final LogType logType;
private final TClass argType;
TLog (LogType logType, TClass argType)
{
this.logType = logType;
this.argType = argType;
}
@Override
protected void buildInputSets(TInputSetBuilder builder)
{
builder.covers(argType, 0);
}
@Override
protected void doEvaluate(TExecutionContext context, LazyList<? extends ValueSource> inputs, ValueTarget output)
{
double input = inputs.get(0).getDouble();
if (logType.isValid(input))
output.putDouble(logType.evaluate(input));
else
output.putNull();
}
@Override
public String displayName()
{
return logType.name();
}
@Override
public TOverloadResult resultType()
{
return TOverloadResult.fixed(argType);
}
}