return function(op)
  return {
    name = 'Better numbers',
    transform = function(e, opts)
      return e.src
      :gsub('%.?%d[%._0-9A-Fa-fxboXBO]+', function(num)
        local base = 10
        local nnum = num
        :gsub('_', '')
        :gsub('^0([xboXBO])', function(m)
          if m == 'x' or m == 'X'
          then base = 16
          elseif m == 'b' or m == 'B'
          then base = 2
          elseif m == 'o' or m == 'O'
          then base = 8
          end
          return ''
        end)
        assert(not nnum:match '[xboXBO]', 'invalid number '..num)
        nnum = tonumber(nnum, base)
        assert(nnum, 'invalid number '..num)
        return tostring(nnum)
      end)
    end,
  }
end