[R] how to overwrite a Unary operator ?

[Greg Snow]

You may be interested in looking at Reference Classes/objects (see
?setRefClass).  This is a form of OO programming that is more similar
to C++ and Java.  You could create a counter object that you could
then increment with syntax like:

x$inc()
x$inc(5)

The first would increment by the default (1), the second would then
increment by 5.



On Fri, Oct 17, 2014 at 2:06 AM, PO SU <rhelpmaillist at 163.com> wrote:
>
> Tks for your alternative way's details. but like you mentioned in graphics package, i still wonder how to overload an operator which can pass one param like +2 .
> There seems exists some examples for my needing. But i try to find them but without any results.
> can you show me some examples from it?
>
>
>
>
>
>
> --
>
> PO SU
> mail: desolator88 at 163.com
> Majored in Statistics from SJTU
>
>
>
> At 2014-10-17 15:16:47, "David Winsemius" <dwinsemius at comcast.net> wrote:
>>
>>On Oct 16, 2014, at 10:36 PM, PO SU wrote:
>>
>>>
>>> Tks for your advice,  let the ++ problem alone, how to write an
>>> Unary operator ? Is it permitted in R?
>>> such    as    a<-2 , a%+2%  will let a  be 4 .
>>
>>OK, that's just wrong. Oh, OK, just for fun, as it were:
>>
>>inc <- function(x)
>>{
>>  eval.parent(substitute(x <- x + 1))
>>}
>>
>>
>> > inc(10)
>>Error in 10 <- 10 + 1 : invalid (do_set) left-hand side to assignment
>> > y=10
>> > inc(y)
>> > y
>>[1] 11
>>
>>
>>> I just want to know it , i won't pollute r with it , because i know
>>> what is r .  : )
>>>
>>It's certainly permitted. Just look at all the overloadings of the "+"
>>operator in graphics packages. Look up the documentation on methods in
>>R.
>>
>>Why not just use a well-behaved function, though?
>>
>>.inc <- function(x) x+1
>> > .inc(10)
>>[1] 11
>>
>>Then you won't be tempted to try 10 <- .inc(10) because it just
>>wouldn't make sense.
>>
>>--
>>David.
>>
>>> --
>>>
>>> PO SU
>>> mail: desolator88 at 163.com
>>> Majored in Statistics from SJTU
>>>
>>>
>>>
>>>
>>> At 2014-10-17 13:09:47, "Rolf Turner" <r.turner at auckland.ac.nz> wrote:
>>>> On 17/10/14 17:29, PO SU wrote:
>>>>>
>>>>> Dear expeRts,
>>>>>   Now i want to know how to implement an Unary operator like  i++
>>>>> in cpp's  synax form.
>>>>>   e.g.   2++  will let 2 be 3 ,  a<-2 ,a++ ,will let a be 3
>>>>> I tried this :
>>>>>  '%++%'<-function(x){
>>>>>    x<<-x+1
>>>>> }
>>>>> but it have problem, the biggest one is it seems the function need
>>>>> twoparams like a%++%b , how to write a function needing just one
>>>>> param?
>>>>>
>>>>> TKS !
>>>>
>>>> Just ***DON'T***.  The "++" operator is useful only for those wish to
>>>> write code which is obscure to the point of incomprehensibility.  It
>>>> makes C and its offspring "write only" languages.
>>>>
>>>> If you are going to use R, use R and don't pollute it with such
>>>> abominations.
>>>>
>>>> cheers,
>>>>
>>>> Rolf Turner
>>>>
>>>>
>>>> --
>>>> Rolf Turner
>>>> Technical Editor ANZJS
>>> ______________________________________________
>>> R-help at 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.
>>
>>David Winsemius, MD
>>Alameda, CA, USA
>>
> ______________________________________________
> R-help at 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.



-- 
Gregory (Greg) L. Snow Ph.D.
538280 at gmail.com