Feature to get or add value to an associative array.

[Cym13]

On Monday, 16 April 2018 at 18:59:54 UTC, Giles Bathgate wrote:
> On Monday, 16 April 2018 at 12:41:07 UTC, JN wrote:
>> It's only one additional "in", but makes the code more 
>> explicit and clear. I think in most cases, you will want to 
>> check if you are dealing with a fetched object or a default 
>> created one, so that will complicate the function even further.
>
> You can still use a combination of `in` and the update syntax 
> if you want, this doesn't take that away. In the future, for a 
> concurrent implementation of associative arrays, a way of 
> getting or adding an element as an atomic operation becomes 
> more important. Either way the beauty of hashed based lookups 
> is that they average O(1), seems a shame to double that up for 
> no reason ;)

"in" returns a pointer to the object, there'es not double lookup 
necessary:

     // if we don't know .get(key, default) exists
     auto ptr   = key in aa;
     auto value = ptr ? *ptr : default;

     // to set default value on the fly
     auto value = ptr ? *ptr : *ptr = default;

is a new flag/method really that necessary? In my experience if 
you have trouble naming it you haven't found its true purpose yet.