gistfile1.vim

function! s:fix_number(pattern, ...)
  if a:0 > 2
    return
  endif

  let s:start = get(a:, 1, get(g:, 'fix_number_default_start', 0))
  let s:step  = get(a:, 2, get(g:, 'fix_number_default_step', 1))

  let pattern = empty(a:pattern) ? get(g, 'fix_number_default_pattern', '\(\d\+\)') : a:pattern

  let s:counter = 0

  silent execute "'<,'>s/".pattern.'/\=s:matched(submatch(1))/g'
endfunction

function! s:matched(match)
  if get(g:, 'fix_number_use_first_number', 0)
    let s:first_number = a:match
  else
    let s:first_number = 0
  endif

  return s:first_number + s:start + s:step()
endfunction

function! s:step()
  let tmp = s:counter
  let s:counter += s:step
  return tmp
endfunction

command! -count -nargs=*
  \	FixNumber
  \	call s:fix_number(<f-args>)