• Trass3r (6/6) Jul 17 2014 void foo(int a, int b = a)
• Timon Gehr (4/10) Jul 18 2014 It could, and I think it is an unnecessary limitation that it currently
• Tove (7/19) Jul 20 2014 This request keeps popping up, I've seen it at least 3 times
• bearophile (8/11) Jul 20 2014 Recently I have had a desire for that feature, to write a
• Andrei Alexandrescu (7/26) Jul 20 2014 The classic example is injecting alloca downstream:

"Trass3r" <un known.com> writes:

void foo(int a, int b = a)
{
}
is illegal in C++ because order of evaluation is undefined.

But since D defines the order to be left to right couldn't it 
also allow this?

Timon Gehr <timon.gehr gmx.ch> writes:

On 07/18/2014 12:00 AM, Trass3r wrote:
 void foo(int a, int b = a)
 {
 }
 is illegal in C++ because order of evaluation is undefined.

 But since D defines the order to be left to right couldn't it also allow
 this?

It could, and I think it is an unnecessary limitation that it currently 
does not. (This can also be useful if that parameter is the hidden 
'this' reference.)

"Tove" <Tove fransson.se> writes:

On Friday, 18 July 2014 at 17:40:23 UTC, Timon Gehr wrote:
 On 07/18/2014 12:00 AM, Trass3r wrote:
 void foo(int a, int b = a)
 {
 }
 is illegal in C++ because order of evaluation is undefined.

 But since D defines the order to be left to right couldn't it 
 also allow
 this?

 It could, and I think it is an unnecessary limitation that it 
 currently does not. (This can also be useful if that parameter 
 is the hidden 'this' reference.)

This request keeps popping up, I've seen it at least 3 times 
before and there's even an enhancement request for it:
https://issues.dlang.org/show_bug.cgi?id=8075

IIRC:
Walter's stance was that he needs compelling examples, which 
proves the utility of this new feature.

"bearophile" <bearophileHUGS lycos.com> writes:

Tove:

 IIRC:
 Walter's stance was that he needs compelling examples, which 
 proves the utility of this new feature.

Recently I have had a desire for that feature, to write a 
function like this:

int[][] generateTable(in uint nx, in uint ny=nx) {...}

If you give just one argument to this function, it generates a 
square table, otherwise it uses both the given sizes.

Bye,
bearophile

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 7/20/14, 2:22 AM, Tove wrote:
 On Friday, 18 July 2014 at 17:40:23 UTC, Timon Gehr wrote:
 On 07/18/2014 12:00 AM, Trass3r wrote:
 void foo(int a, int b = a)
 {
 }
 is illegal in C++ because order of evaluation is undefined.

 But since D defines the order to be left to right couldn't it also allow
 this?

 It could, and I think it is an unnecessary limitation that it
 currently does not. (This can also be useful if that parameter is the
 hidden 'this' reference.)

 This request keeps popping up, I've seen it at least 3 times before and
 there's even an enhancement request for it:
 https://issues.dlang.org/show_bug.cgi?id=8075

 IIRC:
 Walter's stance was that he needs compelling examples, which proves the
 utility of this new feature.

The classic example is injecting alloca downstream:

auto fun(size_t s, void[] buffer = alloca(s)[0 .. s])
{
   ...
}


Andrei