Re: How can one decide between 'not set' and 'not existing?
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- Subject: Re: How can one decide between 'not set' and 'not existing?
- From: Dimiter 'malkia' Stanev <malkia@...>
- Date: 2012年7月25日 14:02:04 -0700
You would have to invent a different nil for that reason, and check
against it.
Somewhere
-- "function() end" would gurantee an unique value, differentiated from
others, unless the VM merges it under one umbrella. Even them, maybe
reusing coroutine might return you an unique value for the lifetime of
the application (or something even simpler)
NULL = function() end
or
NULL = coroutine.create(function()end)
a.key = NULL
and then use NULL as your special null value.
On 7/23/2012 7:50 PM, meino.cramer@gmx.de wrote:
Hi,
Suppose one do
a = { key = nil }
print( a.key )
=> nil
print( a.carkey )
=> nil
It looks like setting a key in a hash with value nil is the
same as if the key does not exist at all.
How can I decide between both in a program?
Is there a 'exists' function as in Perl?
Best regards and thank you very much in advance for any help!
mcc