@ Dirk: For once, you're not quite right. It's not the parser.
One can write methods in R for "+" -- help("+") goes to "Arithmetic operators" and mentions
that these are generic and you can write methods for them ... and of course many package writers do, e.g., we do for the 'Matrix' package, and I also do for the "Rmpfr" package, e.g.
But Dirk is also right (of course!) that you cannot do it in R currently,
by just defining a method for "+.character".
About three years ago, I had started a thread on R-devel (the R mailing list on R development; very much recommended if you are interested in these topics; you can also access through Gmane if you don't want to subscribe) :r-devel archived msg
It came to an interesting discussion with quite a few pros and cons,
notably John Chambers ("the father of S and hence R") pretty strongly opposing to use "+" for an operation that is not commutative,
and also r-devel archived msg2 (by another R-core member), supporting the view that we (R Core) should not adopt / support the idea; and if people **really* wanted it, they could define
%+% for that.
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