• Alex (28/28) Mar 12 2016 Hi all!
• Mike Parker (13/18) Mar 12 2016 Looks like a bug somewhere. The work around is to cast:
• Alex (4/23) Mar 12 2016 Thanks!
• ag0aep6g (3/4) Mar 12 2016 Nicer than a cast: construct a Nullable!int.
• Alex (3/7) Mar 12 2016 ok... so... this makes the error very strange, then... almost
• user42 (6/9) Mar 12 2016 I thought this was supposed to halt with an error rather than
• Alex (9/18) Mar 12 2016 Well, this was not the question. As stated here:
• user42 (3/23) Mar 13 2016 Learned something new. I guess I missed that detail when I read

Alex <sascha.orlov gmail.com> writes:

Hi all!
I have, maybe, a silly question..
Not sure, if
https://forum.dlang.org/post/ibxhuqamgclrcatsyhst forum.dlang.org
has something to do with the topic

Having the following code:

import std.typecons;
import std.algorithm;

void main()
{
     uint[] arr_ref;
     arr_ref.length = 5;
     assert(arr_ref == [0, 0, 0, 0, 0]);
     arr_ref[] = 1;
     assert(arr_ref == [1, 1, 1, 1, 1]);

     Nullable!uint[] arr;
     arr.length = 5;
     bool[] check_arr;
     arr.each!(a => check_arr ~= a.isNull);
     assert(check_arr == [true, true, true, true, true]);

     //arr[] = 1;
     fill(arr, 1);
     assert(arr == [1, 1, 1, 1, 1]);
}

The question is, why the commented out line throws the error:
Error: cannot implicitly convert expression (1) of type int to 
Nullable!uint[],
while the line after that works.

Mike Parker <aldacron gmail.com> writes:

On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote:

     //arr[] = 1;

 The question is, why the commented out line throws the error:
 Error: cannot implicitly convert expression (1) of type int to 
 Nullable!uint[],
 while the line after that works.

Looks like a bug somewhere. The work around is to cast:

arr[] = cast(Nullable!uint)1;

I suggest you file this in the bug tracker [1] if it isn't there 
already. Just use he minimal code that shows the problem:

void main()
{
     import std.typecons;
     Nullable!uint[] arr;
     arr.length = 5;
     arr[] = 1;
}

[1] https://dlang.org/bugstats.php

Alex <sascha.orlov gmail.com> writes:

On Saturday, 12 March 2016 at 15:44:00 UTC, Mike Parker wrote:
 On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote:

     //arr[] = 1;

 The question is, why the commented out line throws the error:
 Error: cannot implicitly convert expression (1) of type int to 
 Nullable!uint[],
 while the line after that works.

 Looks like a bug somewhere. The work around is to cast:

 arr[] = cast(Nullable!uint)1;

 I suggest you file this in the bug tracker [1] if it isn't 
 there already. Just use he minimal code that shows the problem:

 void main()
 {
     import std.typecons;
     Nullable!uint[] arr;
     arr.length = 5;
     arr[] = 1;
 }

 [1] https://dlang.org/bugstats.php

Thanks!
Bug filed under
https://issues.dlang.org/show_bug.cgi?id=15792

ag0aep6g <anonymous example.com> writes:

On 12.03.2016 16:44, Mike Parker wrote:
 arr[] = cast(Nullable!uint)1;

Nicer than a cast: construct a Nullable!int.

arr[] = Nullable!uint(1);

Alex <sascha.orlov gmail.com> writes:

On Saturday, 12 March 2016 at 19:35:30 UTC, ag0aep6g wrote:
 On 12.03.2016 16:44, Mike Parker wrote:
 arr[] = cast(Nullable!uint)1;

 Nicer than a cast: construct a Nullable!int.

 arr[] = Nullable!uint(1);

ok... so... this makes the error very strange, then... almost 
senseless...

user42 <user42 invalid.email> writes:

On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote:
 /snip

I thought this was supposed to halt with an error rather than 
compile and set all members to 1.
The syntax, to me anyways, doesn't really communicate the 
intention of: set all members to 1.
     //arr[] = 1;

Whereas the following does
     fill(arr, 1);

Alex <sascha.orlov gmail.com> writes:

On Saturday, 12 March 2016 at 16:37:25 UTC, user42 wrote:
 On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote:
 /snip

 I thought this was supposed to halt with an error rather than 
 compile and set all members to 1.
 The syntax, to me anyways, doesn't really communicate the 
 intention of: set all members to 1.
     //arr[] = 1;

 Whereas the following does
     fill(arr, 1);


Well, this was not the question. As stated here:
https://dlang.org/spec/arrays.html
in the section "array setting", it is possible to set an array in 
such a manner. And my question was, why a specific array behaves 
not as expected.
So, either there is a problem with filling an array, or, there is 
a problem with implicit conversion of a Nullable!T to its 
underlying type.

user42 <0 0.0> writes:

On Saturday, 12 March 2016 at 18:33:16 UTC, Alex wrote:
 On Saturday, 12 March 2016 at 16:37:25 UTC, user42 wrote:
 On Saturday, 12 March 2016 at 14:33:19 UTC, Alex wrote:
 /snip

 I thought this was supposed to halt with an error rather than 
 compile and set all members to 1.
 The syntax, to me anyways, doesn't really communicate the 
 intention of: set all members to 1.
     //arr[] = 1;

 Whereas the following does
     fill(arr, 1);


 Well, this was not the question. As stated here:
 https://dlang.org/spec/arrays.html
 in the section "array setting", it is possible to set an array 
 in such a manner. And my question was, why a specific array 
 behaves not as expected.
 So, either there is a problem with filling an array, or, there 
 is a problem with implicit conversion of a Nullable!T to its 
 underlying type.

Learned something new. I guess I missed that detail when I read 
that page.