Indexing access for Lists and Maps considered harmful?

[Rémi Forax]

Joseph D. Darcy a écrit :
> Neal Gafter wrote:
>   
>> Why would a language-support method like Puttable.put return a value 
>> that the generated code is required to ignore?  
>>     
>
> I am not proposing that the value is required to be ignored.  My current 
> thinking is that compiler warnings are sufficient to deal with the 
> multiple assignment situation in indexed access. 

Please, no more warning, warnings are not a clear signal for an average Joe.

I am against the use of interfaces like Gettable/Puttable because you 
will have to
rely on generics which doesn't mix well with primitive types.

Some people that are fan of Trove :
http://trove4j.sourceforge.net/index.html

Rémi

>  Aggregates outside 
> java.util.Collection could choose to be Puttable<KeyType, Void.class> to 
> avoid having to return some value.
>
> -Joe
>
>   
>> From the point of view of designing a language-support API, it makes 
>> no sense whatsoever.  The return type is vestigal: it is only present 
>> because of the way that we are considering retrofitting it onto some 
>> existing APIs, but it forces any new APIs that are retrofitted to 
>> return some (arbitrary) value to be ignored.  It also imposes a 
>> performance penalty on implementations that can more efficiently 
>> overwrite a mapping than overwrite AND return the old value.  This is 
>> a language-design smell that suggests we should consider finding 
>> another strategy for getting the effect of index operators.
>>
>> On Tue, Jun 23, 2009 at 10:36 AM, Joseph D. Darcy <Joe.Darcy at sun.com 
>> <mailto:Joe.Darcy at sun.com>> wrote:
>>
>>     spamolovko wrote:
>>
>>     [snip]
>>     >
>>     > PS i remember that coin project had discussion about usage of
>>     special
>>     > interface for "indexing access". That interface have to use it's own
>>     > methods for access to data, so no problems with get semantic.
>>     >
>>     > Example:
>>     >
>>     > public interface Indexer<KeyType, ValueType> {
>>     >
>>     >     public ValueType indexGet(KeyType key);
>>     >
>>     >     public void indexSet(KeyType key, ValueType value);
>>     >
>>     > }
>>     >
>>
>>     [snip]
>>
>>     The idea would be to retrofit new superinterfaces onto the List
>>     and Map
>>     interfaces without adding new methods to the interfaces. For example,
>>     here is a slight refinement of strawman interfaces of that sort
>>     from my
>>     JavaOne talk:
>>
>>     // New superinterfaces to indicate syntax?
>>     interface GettableFromInt<E> {
>>     E get(int);
>>     }
>>
>>     interface Gettable<K, V> {
>>     V get(K k);
>>     }
>>
>>     interface Settable<E> {
>>     E set(int, E e);
>>     }
>>     interface Puttable<K, V> {
>>     V put(K k, V v);
>>     }
>>
>>     java.util.List<E> extends GettableFromInt<E>, Settable<E>, …
>>
>>     java.util.Map<K, V> extends Gettable<Object, V>, Puttable(K, V), …
>>
>>     The names "Gettable" etc. are open to improvement :-)
>>
>>     -Joe
>>
>>
>>     
>
>
>