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Re: NULL vs. ""

2005-05-31 04:21:16

On Mon, May 30, 2005 at 02:31:47PM +0100, Nigel Swinson wrote:

if anyof (header :is "Cc" "", not exists "Cc")

Given that the language definition has no way to express a NULL, I don't
see that as a bad way to state the test.  It's clearer to me than the
regex solution (and the equivalent :matches solution).

Even if there was a way to express a NULL, the following:

What might be nice is if we could say:

if header :is "Cc" NULL  // ie if the header is absent or empty

really wouldn't work either.  A NULL would still have to be different
from the empty string, so you'd have to say:

    if header :is "Cc" [ NULL, "" ]  // if the header is absent or empty

which is indeed slightly tighter and clearer than the 'anyof' test.
Personally I'm not against having a NULL reserved keyword that
represents a missing string value, but it would probably involve a lot
of changes to existing implementations.  I doubt it would be disruptive
to existing sieve scripts though-- only to implementations, thus it
would have to be done via an extension and not a 3028bis addition, and
probably would be quite a bit of an uphill battle.

I think a NULL test of some sort could be useful with variables,
but that's another road that's already been paved...


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