/*
* 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 com.hp.hpl.jena.sparql.algebra.optimize;
import java.util.ArrayList ;
import java.util.List ;
import com.hp.hpl.jena.sparql.algebra.Op ;
import com.hp.hpl.jena.sparql.algebra.TransformCopy ;
import com.hp.hpl.jena.sparql.algebra.Transformer ;
import com.hp.hpl.jena.sparql.engine.binding.Binding ;
import com.hp.hpl.jena.sparql.expr.* ;
/**
* An expression transform that simplifies expressions by constant folding
* wherever possible
*/
public class ExprTransformConstantFold extends ExprTransformCopy {
private Binding b = null;
@Override
public Expr transform(ExprFunction1 func, Expr expr1) {
if (isFoldable(expr1)) {
try {
return func.eval(expr1.getConstant()) ;
} catch (Exception ex) { /* Drop through */ }
}
return super.transform(func, expr1);
}
@Override
public Expr transform(ExprFunction2 func, Expr expr1, Expr expr2) {
if (isFoldable(expr1, expr2)) {
try {
return func.eval(expr1.getConstant(), expr2.getConstant()) ;
} catch (Exception ex) { /* Drop through */ }
}
return super.transform(func, expr1, expr2);
}
@Override
public Expr transform(ExprFunction3 func, Expr expr1, Expr expr2, Expr expr3) {
if (isFoldable(expr1, expr2, expr3)) {
try {
return func.eval(expr1.getConstant(), expr2.getConstant(), expr3.getConstant()) ;
} catch (Exception ex) { /* Drop through */ }
}
return super.transform(func, expr1, expr2, expr3);
}
@Override
public Expr transform(ExprFunctionN func, ExprList args) {
if (isFoldable(args)) {
List<NodeValue> args2 = new ArrayList<>() ;
// Need to "cast" to constants
for ( Expr e : args )
args2.add(e.getConstant()) ;
try {
return func.eval(args2) ;
} catch (Exception ex) { /* Drop through */ }
}
return super.transform(func, args);
}
@Override
public Expr transform(ExprFunctionOp funcOp, ExprList args, Op opArg) {
// Manually transform each argument
Op op = Transformer.transform(new TransformCopy(), this, funcOp.getGraphPattern());
ExprList newArgs = new ExprList();
for (int i = 0; i < args.size(); i++) {
Expr curr = args.get(i);
Expr newArg = ExprTransformer.transform(this, curr) ;
newArgs.add(newArg);
}
return funcOp.copy(newArgs, op);
}
private boolean isFoldable(ExprList exprs) {
for (Expr e : exprs) {
if (e == null || !e.isConstant())
return false;
}
return true;
}
private boolean isFoldable(Expr... exprs) {
for (Expr e : exprs) {
if (e == null || !e.isConstant())
return false;
}
return true;
}
}