dupping to allow vector operation?

[John Colvin via Digitalmars-d-learn]

On Thursday, 9 October 2014 at 18:01:27 UTC, John Colvin wrote:
> On Thursday, 9 October 2014 at 11:29:14 UTC, bearophile wrote:
>> Observe:
>>
>> void main() {
>>     int[3] a1 = [1, 3, 6];
>>     int[]  a2 = a1[] * 3;       // line 3, Error
>>     int[]  a3 = a1.dup[] *= 3;  // line 4, OK?
>>     int[]  a4 = (a1[] * 3).dup; // line 5, Error
>> }
>>
>>
>> Currently the operation in line 4 is accepted:
>>
>> test.d(3,17): Error: array operation a1[] * 3 without 
>> destination memory not allowed
>> test.d(5,18): Error: array operation a1[] * 3 without 
>> destination memory not allowed
>>
>> Is it a good idea to support something like line 5?
>>
>> Bye,
>> bearophile
>
> Why not? Looks fine to me, you've explicitly allocated some new 
> memory for the result to sit in, the lack of which is the 
> motivation for lines 3 an 5 being errors.

To clarify: 4 is good, 3 and 5 are not.