Lambdas in for-each loops

[Remi Forax]

On 09/05/2012 04:19 PM, Maurizio Cimadamore wrote:
> On 05/09/12 15:02, Remi Forax wrote:
>> On 09/05/2012 03:55 PM, Sergey Kuksenko wrote:
>>> On 09/05/2012 05:51 PM, Remi Forax wrote:
>>>> On 09/05/2012 03:26 PM, Brian Goetz wrote:
>>>>>> At such case I have a serious question - why for-each loop doesn't
>>>>>> allow
>>>>>> to use Iterator? Why do we need only Iterable (and arrays of 
>>>>>> course) ?
>>>>>> May be it may sense to expand for-each loop itself and detach the
>>>>>> problem from lambda? it looks like we something like project
>>>>>> Coin2.0 for
>>>>>> such things.
>>>>> This was a hot issue during the development of the foreach loop. In
>>>>> the end, the EG decided that allowing Iterator in foreach loop was
>>>>> potentually confusing, since as a side effect of being iterated, the
>>>>> iterator was "drained".
>>>>>
>>>>>
>>>> Also, you can write horrible things like,
>>>>    Iterator<String> it = collection...
>>>>    for(String s: it) {   // ok, simple loop
>>>>     if (...) {
>>>>        ...
>>>>        it.remove();   // not a simple loop anymore
>>>>      }
>>>>    }
>>>>
>>>> if you read the code, a foreach loop should always be a simple loop
>>>> with no side effect on the iterable.
>>>>
>>>> Rémi
>>>>
>>> Ok. Let's do:
>>>
>>>    Iterator<String> it = collection...
>>>    for(String s: asIterable(it) /*or lambda*/) {   // ok, simple loop
>>>     if (...) {
>>>        ...
>>>        it.remove();   // not a simple loop anymore
>>>      }
>>>    }
>>>
>>> I see the same.
>>>
>> No, because the header of your loop is not simple anymore.
>> BTW, that's why I prefer the lambda syntax, because you add syntax 
>> 'noise',
>> the lambda or the method reference, to the foreach loop,
>> so the fact that's it's a not a plain old loop is clearly visible.
>>
>> for(String s: getACollection()) {  // simple loop
>> }
>>
>> for(String s: () -> getAnIterator()) {  // not a simple loop
>> }
>>
>> As a writer, you pay a syntactic price (burger arrow?) in order to warn
>> the reader.
>>
>> Rémi
>>
>>
> I think that's a weak argument - what about:
>
> List<String> ls = new ArrayList<>();
> ls.add("Hello");
> ls.add("World!");
> for (String s : ls) {
>     if (true) { ls.remove("World!"); }
> }
>
>
> Simple or not simple?

too close to the ConcurrentModificationException for me :)

>
> Maurizio
>
>

Rémi