Perfect. Thank you! > -----Original Message----- > From: Martin Morgan [mailto:[EMAIL PROTECTED] > Sent: 02 May 2006 17:10 > To: Matthew Dowle > Cc: 'Prof Brian Ripley'; "'r-help@/usr/bin/idn: > idna_to_ascii_4z() failed with error 3. > <r-help@stat.math.ethz.ch>"@fhcrc.org > Subject: Re: [R] "a"+"b" > > > I think %any-symbol% defines a binary operator, so > > > "%+%" <- function(x,y) paste(x,y,sep="") > > "a" %+% "b" > [1] "ab" > > > > or for more fun > > > setGeneric("%+%", function(x,y) standardGeneric("%+%")) > [1] "%+%" > > setMethod("%+%", signature(x="character", y="character"), > > function(x,y) paste(x,y,sep="")) > [1] "%+%" > > setMethod("%+%", signature(x="numeric", y="numeric"), function(x,y) > > x+y) > [1] "%+%" > > "a" %+% "b" > [1] "ab" > > 1 %+% 2 > [1] 3 > > > Martin > > Matthew Dowle <[EMAIL PROTECTED]> writes: > > > Thanks for the information. By 'not easily' it sounds like it is > > possible, but how? I'm happy to allow 'errors' like > "2"+"3"="23", is > > that what an erroneous use could be? > > > > I tried the following, given the info in your reply, which > works. But > > is there a way to allow "a"+"b"="ab"? > >> x = "a" > >> `+.character` <- function(e1, e2) paste(e1,e2, sep="") > >> attr(x,"class")="character" > >> x+x > > [1] "aa" > >> > > > >> -----Original Message----- > >> From: Prof Brian Ripley [mailto:[EMAIL PROTECTED] > >> Sent: 02 May 2006 12:03 > >> To: Matthew Dowle > >> Cc: 'r-help@stat.math.ethz.ch' > >> Subject: Re: [R] "a"+"b" > >> > >> > >> Not easily. There's a comment in ?Ops that for efficiency > the group > >> generics only dispatch on objects with a "class" attribute: > >> otherwise you > >> could use an S3 method like > >> > >> `+.character` <- function(e1, e2) paste(e1,e2, sep="") > >> > >> S4 methods are built on top of S3 methods as far as internal > >> dispatch is > >> concerned, so the same comment will apply there AFAICS. > >> > >> I would think that the intention was also to positively > >> discourage messing > >> with the basics of R, as if you were able to do this > >> erroneous uses would > >> likely not get caught. > >> > >> On Tue, 2 May 2006, Matthew Dowle wrote: > >> > >> > > >> > Hi, > >> > > >> > Is there a way to define "+" so that "a"+"b" returns "ab" ? > >> > > >> >> setMethod("+",c("character","character"),paste) > >> > Error in setMethod("+", c("character", "character"), paste) : > >> > the method for function '+' and signature e1="character", > >> > e2="character" is sealed and cannot be re-defined > >> >> "a"+"b" > >> > Error in "a" + "b" : non-numeric argument to binary operator > >> > > >> > Thanks! > >> > > >> > > >> > > >> > [[alternative HTML version deleted]] > >> > > >> > ______________________________________________ > >> > R-help@stat.math.ethz.ch mailing list > >> > https://stat.ethz.ch/mailman/listinfo/r-help > >> > PLEASE do read the posting guide! > >> > http://www.R-project.org/posting-guide.html > >> > > >> > >> -- > >> Brian D. Ripley, [EMAIL PROTECTED] > >> Professor of Applied Statistics, > http://www.stats.ox.ac.uk/~ripley/ > >> University of Oxford, Tel: +44 1865 272861 (self) > >> 1 South Parks Road, +44 1865 272866 (PA) > >> Oxford OX1 3TG, UK Fax: +44 1865 272595 > >> > > > > ______________________________________________ > > R-help@stat.math.ethz.ch mailing list > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide! > > http://www.R-project.org/posting-guide.html >
______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
