How do I distinguish between true, false, and null?
Add this dictionary to your group file:
isFalse ::= ["false":"true"]
It returns true if the value is false, and null otherwise. Then you can use it in 'if statements'.
main(nullValue, falseValue) ::= << $if(isFalse.(falseValue))$ falseValue value is false; $endif$ $if(!isFalse.(nullValue))$ nullValue is NOT false; $endif$ >>