Advanced Usage of Ranges with Vim Keymappings

Question

I have a mapping in my vimrc that downwardly comments out regions of c code:

nmap comc :normal! I//<ESC>

Since the 'normal' ex command implicitly converts input such as "Ncomc" to ".,.+N-1 comc", I can range comments downwardly without many keystrokes and without leaving normal mode. This is, however, a very limited subset of what vim ranges can do. If I'm willing to be verbose, I can achieve upward ranging comments like so:

.,.-5 normal comc 

While editing text, I would much prefer to type something like "-6comc" or make a mapping of "Comc" that uses upward ranges. I'm haven't been able to do so successfully.

Similarly, range operations support commenting until a search pattern is reached, e.g :

.,/int main/ comc

I would, however, like to do so without all that typing.

Answer 1

The behavior you requested is normally done with :h map-operator mapping. With this commenting 3 lines down will turn into comc2j though, but 3 lines up is now just as easy: comc2k.

You can also use visual mode without changing your mapping at all: V2kcomc. You will have to add xnoremap with the identical lhs and rhs because nnoremap works only for normal mode. (And do not use nmap.)

Third option is mapping - to something that moves {count} lines up and puts count back:

nnoremap <expr> - (v:count ? ":\<C-u>\n" . (v:count-1) . 'k' . v:count : '')

. This assumes you are writing 6-comc, not -6comc.

// By the way, I would suggest The NERD Commenter if it comes to the plugin.

Answer 2

While it's commendable to go as far as possible without any plugins, sometimes they're just the best option. What will you do when you start working in a language that has comments with # or (*...*)? Add new mappings for these comment characters?

I recommend commentary.vim which does filetype-aware commenting.

The default commenting operator in commentary.vim is gc. You can combine it with motions, and use it in Visual mode too.

Your use cases:

• Comment downwards N lines (say, 3): :.,.+3normal gcc, or gc3j or 4gcc.

• Comment upwards 5 lines: :.,.-5normal gcc, or simply gc5k.

• Comment until int main: :.,/int main/-1normal gcc, or simply gc/int main followed by Enter.