JESS: add a slot

[William Butler]

I am trying to add a slot to a template from within the jess language.  
From looking at the java API guide and some postings in this archive, I  
think I should be able to do something like:

(bind ?template ((engine) findDeftemplate "some-existing-template"))
(?template addSlot "some-new-slot" (get-member Funcall NIL) "ANY")
to add a blank slot. However a call to (show-deftemplates) then  
generates a NullPointerException reported as

Jess reported an error in routine call
        while executing (call (new jess.PrettyPrinter (call ?__e next))  
toString)
        while executing (printout t crlf (call (new jess.PrettyPrinter  
(call ?__e next)) toString) crlf)
        while executing (while (call ?__e hasNext) (printout t crlf  
(call (new jess.PrettyPrinter (call ?__e next)) toString) crlf))
        while executing deffunction show-deftemplates
        while executing (show-deftemplates).
  Message: Called method threw an exception.
  Program text: ( show-deftemplates )  at line 6.
Nested exception is:
null
java.lang.NullPointerException
        at jess.PrettyPrinter.visitDeftemplate(PrettyPrinter.java:55)
        at jess.Deftemplate.accept(Deftemplate.java:367)
        at jess.PrettyPrinter.toString(PrettyPrinter.java:267)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at  
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.jav 
a:39)
        at  
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessor 
Impl.java:25)

Any hints on how to add a generic slot to an existing template from  
within jess?

Thanks,
Bill Butler
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