TKS , but i still have a question that maybe i can write a new S3 method for +, but how can i create a new operator which can pass one param? becasue + is far away from ++ to let me know that 2 will be 3. So, it's still a question......
-- PO SU mail: desolato...@163.com Majored in Statistics from SJTU At 2014-10-18 01:40:50, "David Winsemius" <dwinsem...@comcast.net> wrote: > >On Oct 17, 2014, at 1:06 AM, PO SU 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? >> > >I think this might be a case of "if you don't know enough to do it, then you >don't know why you shouldn't do it." (Or vice versa?) I did search for a >relevant fortune to support my impression, but the various entries for >fortune("parse") and fortune("eval") didn't seem to hit the mark. > >library(ggplot2) >help(pack="ggplot2") # scroll to bottom of page >ggplot2:::`+.gg` # this shows the S3 method of adding an operator based on >the S3 method dispatch. > >I was able to emulate that example to create a C-like, unary `+` operator for >a new class, but I'm not willing to put it in print for fear that my karmic >account might be depleted. > >-- >David. > >> -- >> >> PO SU >> mail: desolato...@163.com >> Majored in Statistics from SJTU >> >> >> >> At 2014-10-17 15:16:47, "David Winsemius" <dwinsem...@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: desolato...@163.com >>>> Majored in Statistics from SJTU >>>> >>>> >>>> >>>> >>>> At 2014-10-17 13:09:47, "Rolf Turner" <r.tur...@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@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 >>> > >David Winsemius >Alameda, CA, USA > ______________________________________________ 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.