On 05/07/2014 02:45 PM, Simon Urbanek wrote:
On May 7, 2014, at 5:17 PM, Hervé Pagès <hpa...@fhcrc.org> wrote:
On 05/07/2014 12:52 PM, Simon Urbanek wrote:
On May 7, 2014, at 3:37 PM, Hervé Pagès <hpa...@fhcrc.org> wrote:
No big deal. These things can be tricky:
https://stat.ethz.ch/pipermail/r-devel/2006-January/036022.html
Sorry I couldn't resist ;-)
Yeah, but that's just yet another trip down the rabbit hole - why is -2 parsed
as `-`(2) and not a single constant?
You wouldn't want -2 to be parsed as a single constant exactly for
the reason that you wouldn't want -2^2 to return 4. Having -2^2 treated
the same way as -x^2 is a sane feature.
On what grounds? -2 is one value - negative two - and if you square it, you get
four - so that's not even a question of precedence. It's just a matter of
interpretation: do you see the constant -2 or do you see the constant 2 with
unary minus? When you print -2 you get -2 - and that's not a positive constant
with an unary minus - or is it? ;) - aaah, will we ever know … R is good at
hiding that subtlety from us:
a = quote(-2^2)
b = bquote(.(-2)^2)
a
-2^2
b
-2^2
eval(a)
[1] -4
eval(b)
[1] 4
Is there a way to express a negative constant in R? Hmm…
Maybe some people have some use cases for this (speed ?).
Wrong tree ;). You kick-started the trip but failed to follow the path it takes
into the depths of the human mind … :P (or was that computer mind? ;))
BTW I don't see anything deep here, except maybe for the rabbit hole
you've put yourself in. Just sayin'...
H.
Cheers,
Simon
Personally I don't. Of course it would require a special syntax,
something that would probably be as ugly and confusing as the
L suffix used for integer constants (L means long int in C).
H.
On 05/07/2014 09:16 AM, John Chambers wrote:
On 5/7/14, 5:21 AM, Therneau, Terry M., Ph.D. wrote:
Hadley asked about the Blue book; my shelf still has the earlier brown
book
Becker and Chambers, 1984, S: An interactive environment for data
analysis and graphics.
Historically interesting, but there was never a guarantee that Version 3
of S (the "blue book") was back-compatible with earlier versions. We
gave users some help in "getting on the road" to converting, that was
all (see Appendix 4 to the blue book).
For that one brief moment, we felt free to innovate.
John
The manual page for precedence is
$ component select
%x special operator
- unary minus
: sequence operator
^ ** exponentiation
* / mult/div
+ - add/sub
< > <= >= == != logical
! not
& | and/or
<- -> assignment
Terry Therneau
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--
Hervé Pagès
Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M1-B514
P.O. Box 19024
Seattle, WA 98109-1024
E-mail: hpa...@fhcrc.org
Phone: (206) 667-5791
Fax: (206) 667-1319
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
--
Hervé Pagès
Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M1-B514
P.O. Box 19024
Seattle, WA 98109-1024
E-mail: hpa...@fhcrc.org
Phone: (206) 667-5791
Fax: (206) 667-1319
--
Hervé Pagès
Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M1-B514
P.O. Box 19024
Seattle, WA 98109-1024
E-mail: hpa...@fhcrc.org
Phone: (206) 667-5791
Fax: (206) 667-1319
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