[m-rev.] for review: version_hash_table changes

[Paul Bone]

On Mon, May 06, 2013 at 12:08:26PM +1000, Julien Fischer wrote:
>
> Hi Paul,
>
> On Fri, 3 May 2013, Paul Bone wrote:
>
>> diff --git a/library/version_hash_table.m b/library/version_hash_table.m
>> index c624101..4e34f39 100644
>> --- a/library/version_hash_table.m
>> +++ b/library/version_hash_table.m
>> @@ -112,6 +112,19 @@
>>     %
>> :- func num_occupants(version_hash_table(K, V)) = int.
>>
>> +    % Copy the hash table.
>> +    %
>> +    % Even though tables can be 'copied' by just creating a second reference
>> +    % to the same table this does not always allow programmers to reason
>> +    % about performance, as performance depends on how the two references
>> +    % are used after that point.
>> +    %
>> +    % Explicity copying the table with this function makes it easy to see at
>> +    % what points in a program the copying operation occurs, making it
>> +    % easier to reason about performance.
>> +    %
>
> I suggest simply:
>
>        % Make a deep copy of the hash table.
>

It's not a deep copy, because it doesn't copy the items stored in the table.

I still wish to describe the performance implications as this is a case of a
leaky abstraction.


-- 
Paul Bone
http://www.bone.id.au