++
Append two lists, i.e.,
> [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
> [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
If the first list is not finite, the result is the first list.
Symmetric choice.
Symmetric choice.
Create a piece of HTML which is the concatenation of two things which can be made into HTML.
Local, exclusive, left-biased choice: If left parser locally produces any result at all, then right parser is not used.
Local, exclusive, left-biased choice: If left parser locally produces any result at all, then right parser is not used.