Package com.singularsys.jep.misc.nullwrapper

Package to allow the treatment of null values which propagate up through evaluation so that null op anything will be null for most operator. This is similar behaviour SQL with its three value logic. The package works by wrapping existing operators and functions in new operators and functions which will propagate null values.

To set up this functionality use

jep.setComponent(new NullWrappedOperatorTable((OperatorTable2) jep.getOperatorTable(),true));
jep.setComponent(new NullWrappedFunctionTable(jep.getFunctionTable()));
jep.setComponent(new StandardConfigurableParser());
((FastEvaluator) jep.getEvaluator()).setTrapNullValues(false);
((FastEvaluator)jep.getEvaluator()).setTrapUnsetValues(false);

This will include the standard set of operators and functions as well as a Null-safe equals operator <=>.

The logic operators are exceptions to the general rule, true || null

OR Truth table

A OR B	True	False	null
True	True	True	True
False	True	False	null
null	True	null	null

AND Truth table

A AND B	True	False	null
True	True	False	null
False	False	False	False
null	null	False	null

NOT truth table

A	NOT A
True	False
False	True
null	null

Class Summary

Class	Description
NullWrappedFunctionFactory	A factory to create the appropriate type of wrapped function.
NullWrappedFunctionTable	A function table which wraps all the functions in an existing table.
NullWrappedOperatorTable	An operator table where the operators generally return null if either argument is null.

Enum Summary

Enum	Description
NullWrappedOperatorTable.NullWrapperOperators	Key for the one operator NullSafeEquals added by the table.