Re: avoiding recursion in a dump_table function

[Peter Cawley <lua@...>]

On Tue, May 10, 2011 at 4:56 PM, Sean Conner <sean@conman.org> wrote:
> It was thus said that the Great Peter Cawley once stated:
>> On Tue, May 10, 2011 at 4:45 PM, Sean Conner <sean@conman.org> wrote:
>> > It was thus said that the Great Dave Collins once stated:
>> >> I've got a large object which, for convenience of pulling data from it, is self-referencing. (sometimes I need items from a dept, sometimes I need all items).
>> >>
>> >> Essentially, I've got this:
>> >>
>> >> Flyer
>> >>                 Departments
>> >>                                 Dept1
>> >>                                                 Item1
>> >>                                                 Item2
>> >>                                 Dept2
>> >>                                                 Item3
>> >>                                                 Item4
>> >>                 Items
>> >>                                 Item1
>> >>                                 Item2
>> >>                                 Item3
>> >>                                 Item4
>> >>
>> >>
>> >> When I need to look inside this table using the following dump_table method, I get infinite recursion.
>> >>
>> >> Any ideas on how I can add some smarts to my dump_table to defeat the infinite recursion?
>> >>
>> >> function dump_table(t, prefix)
>> >>       if(prefix == nil) then
>> >>             prefix = ""
>> >>       end
>> >>
>> >>       local k,v
>> >>       for k,v in pairs(t) do
>> >>             if(type(v) == "table") then
>> >>                   dump_table(v, prefix .. k .. ":")
>> >>             else
>> >>                   print(prefix .. k .. "=" .. tostring(v))
>> >>             end
>> >>       end
>> >> end
>> >
>> >  Try the following:
>> >
>> > do
>> >  local did_it_already
>> >
>> >  function dump_table(t,prefix,initialized)
>> >
>> >    if not initialized then
>> >      did_it_already = {}
>> >    end
>> >
>> >    local prefix = prefix or ""
>> >
>> >    for k,v in pairs(t) do
>> >      if type(v) == 'table' and not did_it_already[v] then
>> >        did_it_already[v] = true
>> >        dump_table(v,prefix .. k .. ":",true)
>> >      else
>> >        print(prefix .. k .. "=" .. tostring(v))
>> >      end
>> >    end
>> >  end
>> > end
>> >
>> >  The reason you were seeing infinite recursion was because of nested
>> > tables.  This routine keeps track of any tables already processed and skips
>> > them.
>> >
>> >  -spc
>> >
>>
>> Isn't that going to have problems if you ever want to dump the same
>> table more than once?
Ah yes, sorry for the noise; I read it too fast and thought that
initialized had a similar lifetime to did_it_already.