From Kurt.Hornik@ci.tuwien.ac.at  Mon Apr 14 09:04:34 1997
From: Kurt.Hornik@ci.tuwien.ac.at (Kurt Hornik)
Date: Mon, 14 Apr 1997 10:04:34 +0200
Subject: R-alpha: jpn() port
In-Reply-To: <x2hghhtal8.fsf@bush.kubism.ku.dk>
References: <199704081803.UAA13610@aragorn.ci.tuwien.ac.at>
 <x2hghhtal8.fsf@bush.kubism.ku.dk>

>>>>> Peter Dalgaard BSA writes:

> Kurt Hornik <Kurt.Hornik@ci.tuwien.ac.at> writes:
>> Finally, here's something that's also been on my mind for some time now
>> (and also needed help in the port).  Code like
>> 
>> if(all(names(x)) == c("x", "y"))
>> 
>> fails if names(x) is NULL.  Is that really necessary?  (More precisely,
>> obviously we only want to test whether the two objects have equal
>> values, a la Lisp `equal').

> According to my parenthesis count, that expression will fail in any
> case!

Yes ... I meant

	if(all(names(x) == c("x", "y")))

> However, I get your drift. Splus has
>> all(NULL)
> [1] T
>> any(NULL)
> [1] F

> Which makes sense for cases like yours. R should probably conform to
> this.

Actually, I am not sure about that, but it does not solve the problem.
If you look at the code in the S jpn package, it contains

	if(all(names(region) == c("x", "y")))

If region has no names attribute,

	all(names(region) == c("x", "y"))

gives NA and if(NA) (correctly) gives ``Error: Missing value where
logical needed''.  The problem is that NULL == something gives NA.
(Should it really do that?)

But perhaps it is better anyway to force the programmer to check for
NULL values before comparisons ...

-k

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R-alpha: jpn() port
Kurt Hornik