How to update a number inside a tuple stored in an ets table?

Question

Suppose I have an ets table like:

I = ets:new(mytable, [named_table, set]).
ets:insert(I, {10,{10, 4 ,"description"}).

I would like to update the element 4 using the ets:update_counter.

I tried in different way, but can't find the solution, for example:

ets:update_counter(I, 10 , {3,1}).

** exception error: bad argument
     in function  ets:update_counter/3
        called as ets:update_counter(mytable,10,{3,1})

I'd like to have the result as:

{10,{10, 5 ,"description"}

Headcheese

Answer 1

I recommend to use just one tuple for key and values, instead of using a tuple for values in another tuple:

1> I = ets:new(mytable, [named_table, set]).
mytable
2> ets:insert(I, {10, 10, 4 ,"description"}).
true
3> ets:update_counter(I, 10 , {3,1}).        
5
4> ets:lookup(I, 10).
[{10,10,5,"description"}]

Overly

I know that, I was looking how to solve my problem. Thanks btw – Headcheese

@Headcheese If you really need to use update_counter you will need to flatten your tuple, i.e. the value part can't be a tuple. update_counter doesn't support that. Assuming that the key and the first position in the value tuple is always the same you could add wrapper functions for inserting/reading to/from the ets table. The insert would just insert the value part and the read could create the nested tuple that you have today. – Azo