Comment and uncomment by the same key strokes

Question

At the moment, my commenting and un-commenting is done by two different strokes listed below:

nnoremap <leader>c 0<insert>//<Esc>
nnoremap <leader><leader>c :s;^\s*//<cr>

Which is tedious for me, can someone help me to write a mapping macro that <leader>c stroke removes the comments, if there are any, or add one otherwise.

If the comments/uncomments will all be done by the single lovely <leader>c, that would be a lot less pain in my ......

Thanks!

p.s.

If you intended to learn Vimrc, read the answer, try those cool solutions. However, here comes the better pain killer: NERD Commenter,

Answer 1

You can achieve this kind of effect simply with an expression map and the ternary operator:

nnoremap <expr> <leader>c getline('.')[0:1] == '//'
  \ ? ":s;^\s*//<cr>"
  \ : "0<insert>//<Esc>"

An expression mapping maps your <leader>c to the result of an expression. In this case, it tests if the first two character in the line are // and then carries one of the commands you already wrote.

For more details, see:

• :help :map-expression
• :help expr1

Answer 2

If you want to use your own mappings you can try something like this:

nnoremap <expr> <Leader>c IsCommented() ? ":s;^\s*//<cr>" : "0<insert>//<Esc>"

function! IsCommented()
    return substitute(getline('.'), '^\s*', '', '')[0] == "/" && substitute(getline('.'), '^\s*', '', '')[0] == substitute(getline('.'), '^\s*', '', '')[1]
endfunction

IsCommented() will return true is the first two characters of the current line are / and false otherwise (note that it will ignore the leading whitespaces) and the mapping is conditioned by the result of this command (See :h :map-expression)

However, I would recommend not to reinvent the wheel and use a plugin like NERDCommenter or vim-commentary which are pretty powerful and lightweight.

Edit As @Rich said: tcomment never gets any love.