Lambdas in for-each loops

[Remi Forax]

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