Re: avoiding recursion in a dump_table function

[Peter Cawley <lua@...>]

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?