defining operator doesn't work anymore (Error in UseMethod(“%op%”): no applicable method for '%op%' applied to an object of class “character”)

Question

In my toy package, I have defined %+% operator as an alias to paste0(). Trying to reduce interference with other packages, I realized it the follow

Answer 1

To export S3 methods, your NAMESPACE file needs to (in your case) contain the following declarations:

export(`%+%`)
S3method(`%+%`, default)
S3method(`%+%`, character)
S3method(`%+%`, numeric)

That is, export the %+% generic, and declare S3 methods for the methods.

Better yet, instead of manually editing the NAMESPACE file use ‘roxygen2’, which generates the correct declarations for you based on the @export documentation tag.