• bearophile (15/15) Oct 09 2014 Observe:
• John Colvin (4/19) Oct 09 2014 Why not? Looks fine to me, you've explicitly allocated some new
• John Colvin (2/27) Oct 10 2014 To clarify: 4 is good, 3 and 5 are not.
• "Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> (8/21) Oct 09 2014 It's equivalent to:
• bearophile (4/11) Oct 09 2014 So do we need a new different syntax to do it? :-)

"bearophile" <bearophileHUGS lycos.com> writes:

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

"John Colvin" <john.loughran.colvin gmail.com> writes:

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.

"John Colvin" <john.loughran.colvin gmail.com> writes:

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.

"Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> writes:

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?

It's equivalent to:

     int[] tmp = a1[] * 3;
     int[] a4 = tmp.dup;

The first part is of course identical to line 3, so this should 
be an error, too. Normal rules for evaluation order require `a1[] 
* 3` to be evaluated before `(...).dup`, so where is it supposed 
to store the intermediate result?

"bearophile" <bearophileHUGS lycos.com> writes:

Marc Schütz:

 It's equivalent to:

     int[] tmp = a1[] * 3;
     int[] a4 = tmp.dup;

 The first part is of course identical to line 3, so this should 
 be an error, too. Normal rules for evaluation order require 
 `a1[] * 3` to be evaluated before `(...).dup`, so where is it 
 supposed to store the intermediate result?

So do we need a new different syntax to do it? :-)

Bye,
bearophile