On Mon, 29 Sep 2003, Donald G Porter wrote:
>  The two seemingly analogous operations are opposite in the
>  expectations they fulfill.
> 
>    During a variable unset trace, the traced variable is already
>    unset, but the trace has the power to recreate it.
> 
>    During a command delete trace, the traced command still exists,
>    but will be deleted following the trace, and the trace can't do
>    anything to stop it.
> 
>  Is there an intentional design reason behind these differences?  Can
>  someone explain it?

As the person who originally implemented command-delete traces, I can say
there is no strong intentional design behind the differences.  In fact if
I were to submit a TIP now to introduce command delete/rename traces I
would prefer to make them more like variable traces.  I vaguely recall
seeing something in the code that suggested making 'rename foo {}' not
delete 'foo' would be quite problematic, but I don't recall exactly what
that was.  Certainly I don't have code that depends on the above design.

Vince.



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