R-alpha: ==NULL
Martin Maechler
Martin Maechler <maechler@stat.math.ethz.ch>
Thu, 1 May 97 17:47:36 +0200
>>>>> "Tom" == Thomas Lumley <thomas@biostat.washington.edu> writes:
Tom> Any comparison with NULL generates an error Error: comparison is
Tom> possible only for vector types whereas in S(-PLUS) it gives NA,
Tom> which seems more sensible.
Tom> Along similar lines, comparison with a length 0 vector returns
Tom> logical(0) in R but NA in S.
Is n't logical(0) more logical than NA ?
I agree that it would be best (convenience)
if 'NULL==1' returned the same as 'numeric(0)==1'.
At the moment, I don't see why compatibility with S should be important
here:
if( NULL == anything)
or, e.g., if( numeric(0) == numeric(0) )
give an error anyway, i.e., you have to test for length 0 _anyway_
in the cases where one comparison argument may have zero length.
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