The dot object is defined so that idiom like .[x,y] returns
the commutator, that is, xy-yx.
The dot object is generated by running script inst/dot.Rmd,
which includes some further discussion and technical documentation,
and creates file dot.rda which resides in the data/
directory.
The borcherds vignette discusses this in a more general
context.
Value
Always returns an object of the same class as xy.
Arguments
x
Object of any class
i,j
elements to commute
...
Further arguments to dot_error(), currently ignored