/**
* Methods to create a {@link Function} starting from a {@link IsNullExpression}
*
* @param pred IsNullExpression
* @param lookupTable
* @return a function from the OBDADataFactory
*/
private Function getFunction(IsNullExpression pred, LookupTable lookupTable) {
Expression column = pred.getLeftExpression();
String columnName = column.toString();
String variableName = lookupTable.lookup(columnName);
if (variableName == null) {
throw new RuntimeException("Unable to find column name for variable: " + columnName);
}
Term var = dfac.getVariable(variableName);
if (!pred.isNot()) {
return dfac.getFunctionIsNull(var);
} else {
return dfac.getFunctionIsNotNull(var);
}
}
public void visit(IsNullExpression isNullExpression) throws Exception {
isNullExpression.getLeftExpression().accept(this);
}