Vim: Relative Number Toggle

.vimrc-relativenumbers

" Function: RELATIVENUMBER"{{{
set relativenumber
" toggle line numbering mode
if exists("+relativenumber")
    if v:version >= 400
        set number
    endif
    set relativenumber  " show relative line numbers
    set numberwidth=3   " narrow number column
    " cycles between relative / absolute / no numbering
    if v:version >= 400
        function! RelativeNumberToggle()
            if (&number == 1 && &relativenumber == 1)
                set nonumber
                set relativenumber relativenumber?
            elseif (&number == 0 && &relativenumber == 1)
                set norelativenumber
                set number number?
            elseif (&number == 1 && &relativenumber == 0)
                set norelativenumber
                set nonumber number?
            else
                set number
                set relativenumber relativenumber?
            endif
        endfunc
    else
        function! RelativeNumberToggle()
            if (&relativenumber == 1)
                set number number?
            elseif (&number == 1)
                set nonumber number?
            else
                set relativenumber relativenumber?
            endif
        endfunc
    endif
    nnoremap <silent> <leader>z :call RelativeNumberToggle()<CR>
else                  " fallback
    set number          " show line numbers
    " inverts numbering
    nnoremap <silent> <leader>z :set number! number?<CR>
endif
"}}}