Comment uncomment

vimrc

" Home-brewed commenter and uncommenter
" :Comment and :Uncomment will comment out a given range of lines
" or visual selection.
" Comment marks will be placed at beginning of line, and only comment
" marks at the beginning of lines will be uncommented.
" Comment mark will dynamically determined to be '#', '//' or '--' depending
" on file extension of the file in buffer, and '#' if none can be detected.

func! CommentMarker()
  let ext = expand('%:e')
  if ext == 'js'
    return '//'
  elseif ext == 'hs' || ext == 'elm'
    return '--'
  elseif ext == 'html'
    return '<!-- '
  else
    return '#'
  endif
endfunc
func! Comment() range
  let lnum = a:firstline
  while lnum <= a:lastline
    let line = getline(lnum)
    let newline = substitute(line, '^', CommentMarker() . ' ', '')      " comment out
    call setline(lnum, newline)
    let lnum += 1
  endwhile
endfunc
func! Uncomment() range
  let lnum = a:firstline
  while lnum <= a:lastline
    let line = getline(lnum)
    let newline = substitute(line, '^'.CommentMarker().'\s\?', '', '')   " uncomment
    call setline(lnum, newline)
    let lnum += 1
  endwhile
endfunc
command! -bar -range Comment :<line1>,<line2>call Comment()
command! -bar -range Uncomment :<line1>,<line2>call Uncomment()