overloading + operator for chars

An embedded and charset-unspecified text was scrubbed...
Name: not available
URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20111102/7a1e5368/attachment.pl>
Hello,

I would like to overload the "+" operator so that it can be used to concatenate two strings, e.g "John" + "Doe" = "JohnDoe".
How can I 'unseal' the "+" method?
setMethod("+", signature(e1="character", e2="character"), function(e1, e2) paste(e1, e2, sep="") )
Error in setMethod("+", signature(e1 = "character", e2 = "character"),  :
   the method for function "+" and signature e1="character", e2="character" is sealed and cannot be re-defined

Hi -- I think the two issues are that "+" is part of the "Arith" group 
generic (?Methods, ?Arith) and that `+` (actually, members of the Ops 
group) for primitive types dispatches directly without doing method 
look-up. Personally I might

setClass("Character", contains="character")

Character <- function(...) new("Character", ...)

setMethod("Arith", c("Character", "Character"), function(e1, e2) {
     switch(.Generic,
            "+"=Character(paste(e1, e2, sep="")),
            stop("unhandled 'Arith' operator '", .Generic, "'"))
})

and then

 > Character(c("foo", "bar")) + Character("baz")
[1] "foobaz" "barbaz"

Some might point to

 > `%+%` <- function(e1, e2) paste(e1, e2, sep="")
 > "foo" %+% "bar"
[1] "foobar"

Martin
Cheers!!
Albert-Jan

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	[[alternative HTML version deleted]]

______________________________________________
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.

Computational Biology
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N. PO Box 19024 Seattle, WA 98109

Location: M1-B861
Telephone: 206 667-2793