Vim Latex Dollar Text Objects

" latex $text-objects$

function! s:ADollar()
  if search('\m\%#\$', 'bcnW')
" On $
    if search('\m\_.\+\$', 'nW')
      return "/\\$\<CR>"
    elseif search('\m\$\_.\+\%#', 'bnW')
      return "?\\$\<CR>"
    else
      return "\<C-\>\<C-n>\<Esc>"
    endif
  elseif search('\m\$\%(\%(\$\)\@!\_.\)*\%#\_.\{-}\%(\$\)', 'bcnW')
" Between $ and $
    return "?\\$\<CR>o/\\$\<CR>"
  endif
" Return to normal mode and sound a bell.
  return "\<C-\>\<C-n>\<Esc>"
endfunction

function! s:IDollar()
  let vad = s:ADollar()
  if vad !~ '\m[\x1b]' " If the result contains an <Esc>, not in a dollar
    return vad . 'owoge'
  endif
  return vad
endfunction

vnoremap <expr> a$ <SID>ADollar()
vnoremap <expr> i$ <SID>IDollar()
onoremap a$ :normal va$<CR>
onoremap i$ :normal vi$<CR>