[R] are arithmetic comparison operators binary?
the man page for relational operators (see, e.g., ?'') says:
Binary operators which allow the comparison of values in atomic vectors.
Arguments:
x, y: atomic vectors, symbols, calls, or other objects for which
methods have been written.
it is somewhat surprizing that the following works:
''(1)
# logical(0)
''()
# logical(0)
''(1,2,3)
# TRUE
what does 'binary' mean here, precisely? in the first two examples, one
might suspect that '' treats the missing arguments as missing values,
but this would not be coherent with what the man page says:
Missing values ('NA') and 'NaN' values are regarded as
non-comparable even to themselves, so comparisons involving them
will always result in 'NA'.
i can't find the above explained in the documentation. typing `` shows
that it is a
function(e1, e2) .Primitive()
how come can/should it work with no complaint on input that does not
consist of exactly 2 arguments?
in scheme (which is claimed to have been an inspiration for r), works
on an arbitrary number of arguments:
()
;; #t
( 1)
;; #t
( 1 2 3)
;; #t
( 1 2 0)
;; #f
but there is an arity-dispatched procedure, not a binary one, and it
produces sensible output for any number of arguments (arguably for n=0, 1).
vQ
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Re: [R] are arithmetic comparison operators binary?
WK == Wacek Kusnierczyk waclaw.marcin.kusnierc...@idi.ntnu.no
on Mon, 23 Feb 2009 12:06:32 +0100 writes:
Thank you, Wacek,
though .. wrong mailing list
WK the man page for relational operators (see, e.g., ?'') says:
WK
WK Binary operators which allow the comparison of values in atomic vectors.
WK Arguments:
WK x, y: atomic vectors, symbols, calls, or other objects for which
WK methods have been written.
WK
WK it is somewhat surprizing that the following works:
WK ''(1)
WK # logical(0)
WK ''()
WK # logical(0)
WK ''(1,2,3)
WK # TRUE
a bit surprising (sic!), indeed, even for me.
Thanks for your notice and report!
If you'd looked a bit in the sources, you'd seen that they
really are supposed to be binary only.
A very small change in the sources does accomplish this, passes
the standard checks (and I cannot imagine reasonable code that
would have relied on the more lenient behavior), so
this will have changed in one of the next versions of R-devel.
Martin Maechler, ETH Zurich
WK what does 'binary' mean here, precisely? in the first two examples, one
WK might suspect that '' treats the missing arguments as missing values,
WK but this would not be coherent with what the man page says:
WK
WK Missing values ('NA') and 'NaN' values are regarded as
WK non-comparable even to themselves, so comparisons involving them
WK will always result in 'NA'.
WK
WK i can't find the above explained in the documentation. typing `` shows
WK that it is a
WK function(e1, e2) .Primitive()
WK how come can/should it work with no complaint on input that does not
WK consist of exactly 2 arguments?
WK in scheme (which is claimed to have been an inspiration for r), works
WK on an arbitrary number of arguments:
WK ()
WK ;; #t
WK ( 1)
WK ;; #t
WK ( 1 2 3)
WK ;; #t
WK ( 1 2 0)
WK ;; #f
WK but there is an arity-dispatched procedure, not a binary one, and it
WK produces sensible output for any number of arguments (arguably for n=0,
1).
WK vQ
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] are arithmetic comparison operators binary?
Martin Maechler wrote: WK == Wacek Kusnierczyk waclaw.marcin.kusnierc...@idi.ntnu.no on Mon, 23 Feb 2009 12:06:32 +0100 writes: Thank you, Wacek, though .. wrong mailing list apologies. i was actually asking for explanation, assuming that it might be my misunderstanding, rather than reporting a bug. WK the man page for relational operators (see, e.g., ?'') says: WK WK Binary operators which allow the comparison of values in atomic vectors. WK Arguments: WK x, y: atomic vectors, symbols, calls, or other objects for which WK methods have been written. WK WK it is somewhat surprizing that the following works: WK ''(1) WK # logical(0) WK ''() WK # logical(0) WK ''(1,2,3) WK # TRUE a bit surprising (sic!), indeed, even for me. Thanks for your notice and report! you're welcome. shouldn't the tests have captured it? i think you should have a check for every feature following from the docs. plus those undocumented, but assumed by the developers. If you'd looked a bit in the sources, you'd seen that they really are supposed to be binary only. it wouldn't be nonsensical to let them be of arbitrary arity (in a well-documented manner), though it might confuse users. A very small change in the sources does accomplish this, passes the standard checks (and I cannot imagine reasonable code that would have relied on the more lenient behavior), so this will have changed in one of the next versions of R-devel. thanks. just a question (i haven't checked the sources, maybe i should): what is it that happens when one of the operators is called with n = 0 or 1 argument? how does it come up with logical(0) rather than NA? cheers, vQ __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
