How to get the number used before a command as an argument?

Question

How can I write a function that can be invoked in normal mode with regular keystrokes like {myNumber}<Leader>p, and prints {myNumber} into the current buffer.

---

For example: here's a command to format highlighted text to a variable width (dubiously useful, but an effective POC)

vnoremap 80w <ESC>:set textwidth=80<CR>'<gq'>, which turns the visual mode keystroke 80w to a command: wrap the visually selected text to 80 columns.

I want to make this a function that takes user input instead of the hard-coded value of 80. Furthermore, as a function I wouldn't have to clobber the value of textwidth.

So I ask: how do I read the number that comes before a keystroke as a argument to a function?

---

edit: here's the setup that I'm now using:

function! SetTabs(num)
  let myCommand = printf("set tabstop=%d softtabstop=%d shiftwidth=%d",
\   a:num, a:num, a:num)
  execute l:myCommand
  echo "Changed tabs to be worth " . a:num
endfunction

noremap <Leader>tab :<C-u>call SetTabs(v:count1)<CR>

Answer 1

You can use v:count/v:count1 to get the current count. Use execute/let to accomplish these type of mappings:

xnoremap <leader>w :<c-u>execute 'set textwidth='.v:count<cr>gvgq
xnoremap <leader>w :<c-u>let &textwidth=v:count<cr>gvgq

For more information see:

:h v:count
:h v:count1
:h :execute
:h c_CTRL-U
:h :let-&
:h gv