BasicOperator's %eval property

Greetings Axiom gurus! Here's some more weirdness that I'd like to
understand better. I snipped all the "Loading ..." messages. Any
hints?

Thanks.

Igor


(3) -> feval1(x:INT):INT == x^2
   Function declaration feval1 : Integer -> Integer has been added to
      workspace.
                                                                   Type: Void
(4) -> feval1(10)
   Compiling function feval1 with type Integer -> Integer

   (4)  100
                                                        Type: PositiveInteger
(5) -> feval2(x:EXPR INT):EXPR INT == x^2
   Function declaration feval2 : Expression Integer -> Expression
      Integer has been added to workspace.
                                                                   Type: Void
(6) -> feval2(10)

   (6)  100
                                                     Type: Expression Integer
(7) -> f := operator 'f
(7) ->
   (7)  f
                                                          Type: BasicOperator
(8) -> evaluate(f,feval2) -- from BOP1, assigns the %eval property
(8) ->
   (8)  f
                                                          Type: BasicOperator
(9) -> f(10)
(9) ->
   (9)  100
                                                     Type: Expression Integer
(10) -> evaluate(f,feval1)
(10) ->
   (10)  f
                                                          Type: BasicOperator
(11) -> f(10)
 11) ->
   >> System error:
   ((0 . 10) 0 . 1) is not of type NUMBER.