>>You can only use built-in functions in #IF.
>>To control what to compile, you would use #IFDEF/#IFNDEF in combination with #DEFINE/#UNDEF
>>
>>>
>
>By built-in functions do you mean those that are compiled? And if I use #IFDEF/#IFDNED, I still can't use them when running/testing the application in IDE, right?

You can probably define something like

#DEFINE DEBUG .T.

Then

#IF DEBUG
My IDE Code
#ELSE
My Production Code
#ENDIF