class TQFilterObservable: public TQObservable

 default constructor

 default destructor

 retrieve the list of branch names
 ownership of the list belongs to the caller of the function

 determine all return values for getValueAt and getNevaluations if this hasn't been done yet

 in the rest of this function, you should retrieve the data and calculate your return value
 here is the place where most of your custom code should go
 a couple of comments should guide you through the process
 when writing your code, please keep in mind that this code can be executed several times on every event
 make your code efficient. catch all possible problems. when in doubt, contact experts!

 constructor with expression argument

 retrieve the expression associated with this observable

 check if this observable type knows expressions

 set the expression to a given string

 parse the expression

 retrieve the expression associated with this incarnation

 initialize self - compile container name, construct accessor

 finalize self - delete accessor