package com.bigdata.rdf.sparql.ast;
import java.util.Map;
import com.bigdata.bop.BOp;
import com.bigdata.bop.IConstant;
import com.bigdata.bop.IValueExpression;
import com.bigdata.bop.IVariableOrConstant;
import com.bigdata.rdf.internal.IV;
import com.bigdata.rdf.model.BigdataValue;
/**
* Used to represent a variable or constant in the AST (a term in a statement
* pattern for example). Unlike {@link FunctionNode}s, a {@link TermNode} models
* the {@link IValueExpression} directly as its sole child argument. This
* facilitates various rewrite patterns in which variables are renamed, etc.
*
* @author mikepersonick
*/
public abstract class TermNode extends ValueExpressionNode {
/**
*
*/
private static final long serialVersionUID = 2050144811725774174L;
/**
* Constructor required for {@link com.bigdata.bop.BOpUtility#deepCopy(FilterNode)}.
*/
public TermNode(TermNode op) {
super(op);
}
/**
* Required shallow copy constructor.
*/
public TermNode(final BOp[] args, final Map<String, Object> anns) {
super(args, anns);
}
/**
* Strengthen the return type.
*/
@Override
public IVariableOrConstant<IV> getValueExpression() {
return (IVariableOrConstant<IV>) get(0);
}
/**
* Operation is not supported (could be modeled by changing args[0] if we
* still want to do this).
*/
@Override
public void setValueExpression(IValueExpression<? extends IV> ve) {
throw new UnsupportedOperationException();
}
/**
* NOP.
*/
@Override
final public void invalidate() {
// NOP
}
final public BigdataValue getValue() {
final IVariableOrConstant<IV> val = getValueExpression();
if (val != null && val instanceof IConstant) {
final IV iv = val.get();
if (iv.hasValue()) {
return iv.getValue();
}
}
return null;
}
@Override
public String toString(int i) {
return toShortString();
}
}