Fix bug: Add support for de-referencing pointers to struct (struct_ptr^.elem1) when used inside FB.
Note that multiple de-referencing of structs (struct_ptr_ptr^^.elem) is not supported inside FB code (this would need BIG changes to the compiler!)
FUNCTION_BLOCK DERIVATIVE
VAR_INPUT
RUN : BOOL ; (* 0 = reset *)
XIN : REAL ; (* Input to be differentiated *)
CYCLE : TIME ; (* Sampling period *)
END_VAR
VAR_OUTPUT
XOUT : REAL ; (* Differentiated output *)
END_VAR
VAR X1, X2, X3 : REAL ; END_VAR
IF RUN THEN
XOUT := (3.0 * (XIN - X3) + X1 - X2)
/ (10.0 * TIME_TO_REAL(CYCLE)) ;
X3 := X2 ; X2 := X1 ; X1 := XIN ;
ELSE XOUT := 0.0; X1 := XIN ; X2 := XIN ; X3 := XIN ;
END_IF ;
END_FUNCTION_BLOCK