Here, the _nn fragment does not mean a literal doubled letter "n", but is a pattern used to indicate that there should be a number at this place. Therefore, it is more logical to write it in brackets (such as <nn>, or even better <number>) to convey the information that this is not a literal, but a pattern.
Here, the
_nn
fragment does not mean a literal doubled letter "n", but is a pattern used to indicate that there should be a number at this place. Therefore, it is more logical to write it in brackets (such as<nn>
, or even better<number>
) to convey the information that this is not a literal, but a pattern.