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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.searchlib.rankingexpression.transform;
import com.yahoo.searchlib.rankingexpression.Reference;
import com.yahoo.searchlib.rankingexpression.evaluation.TensorValue;
import com.yahoo.searchlib.rankingexpression.evaluation.Value;
import com.yahoo.searchlib.rankingexpression.rule.CompositeNode;
import com.yahoo.searchlib.rankingexpression.rule.ConstantNode;
import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
import java.util.ArrayList;
import java.util.List;
/**
* Replaces constant reference pseudofeatures which are scalars by their constant value
*
* @author bratseth
*/
public class ConstantDereferencer extends ExpressionTransformer<TransformContext> {
@Override
public ExpressionNode transform(ExpressionNode node, TransformContext context) {
if (node instanceof ReferenceNode)
return transformFeature((ReferenceNode) node, context);
else if (node instanceof CompositeNode)
return transformChildren((CompositeNode)node, context);
else
return node;
}
/** Returns true if the given reference is an attribute, constant or query feature */
// TEMP: from config-model module
public static boolean isSimpleFeature(Reference reference) {
if ( ! reference.isSimple()) return false;
String name = reference.name();
return name.equals("attribute") || name.equals("constant") || name.equals("query");
}
private ExpressionNode transformFeature(ReferenceNode node, TransformContext context) {
if ( ! node.getArguments().isEmpty() && ! isSimpleFeature(node.reference()))
return transformArguments(node, context);
else
return transformConstantReference(node, context);
}
private ExpressionNode transformArguments(ReferenceNode node, TransformContext context) {
List<ExpressionNode> arguments = node.getArguments().expressions();
List<ExpressionNode> transformedArguments = new ArrayList<>(arguments.size());
for (ExpressionNode argument : arguments)
transformedArguments.add(transform(argument, context));
return node.setArguments(transformedArguments);
}
private ExpressionNode transformConstantReference(ReferenceNode node, TransformContext context) {
String name = node.getName();
if (node.reference().name().equals("constant")) {
ExpressionNode arg = node.getArguments().expressions().get(0);
if (arg instanceof ReferenceNode) {
name = ((ReferenceNode)arg).getName();
}
}
Value value = context.constants().get(name); // works if "constant(...)" is added
if (value == null || value.type().rank() > 0) {
return node; // not a number constant reference
}
return new ConstantNode(value.freeze());
}
}
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