• TC (24/24) Jul 19 2015 I tested the code from: http://dlang.org/struct.html
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (5/29) Jul 19 2015 The docs are not clear: s and t are not meant to be module-scope
• "Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> (6/44) Jul 20 2015 I think that's not what the OP means. The documentation is indeed
• Dicebot (7/9) Jul 20 2015 Docs are wrong here. `static opCall` was never intended to be

"TC" <chalucha gmail.com> writes:

I tested the code from: http://dlang.org/struct.html
Section: Dynamic Initialization of Structs


struct S
{
     int a;

     static S opCall(int v)
     {
         S s;
         s.a = v;
         return s;
     }

     static S opCall(S v)
     {
         S s;
         s.a = v.a + 1;
         return s;
     }
}

S s = 3; // sets s.a to 3
S t = s; // sets t.a to 3, S.opCall(s) is not called

which does not compile (Error: cannot implicitly convert 
expression (3) of type int to S).

What is wrong here? Docs or behavior? Tested it on asm.dlang.org 
where it fails with all compiler versions.

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 07/19/2015 03:26 AM, TC wrote:
 I tested the code from: http://dlang.org/struct.html
 Section: Dynamic Initialization of Structs


 struct S
 {
      int a;

      static S opCall(int v)
      {
          S s;
          s.a = v;
          return s;
      }

      static S opCall(S v)
      {
          S s;
          s.a = v.a + 1;
          return s;
      }
 }

 S s = 3; // sets s.a to 3
 S t = s; // sets t.a to 3, S.opCall(s) is not called

 which does not compile (Error: cannot implicitly convert expression (3)
 of type int to S).

 What is wrong here? Docs or behavior? Tested it on asm.dlang.org where
 it fails with all compiler versions.

The docs are not clear: s and t are not meant to be module-scope 
variables, which should be initialized in a 'static this()' (or 'shared 
static this()'). Put them inside a function like main() and it works fine.

Ali

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

On Sunday, 19 July 2015 at 13:25:41 UTC, Ali Çehreli wrote:
 On 07/19/2015 03:26 AM, TC wrote:
 I tested the code from: http://dlang.org/struct.html
 Section: Dynamic Initialization of Structs


 struct S
 {
      int a;

      static S opCall(int v)
      {
          S s;
          s.a = v;
          return s;
      }

      static S opCall(S v)
      {
          S s;
          s.a = v.a + 1;
          return s;
      }
 }

 S s = 3; // sets s.a to 3
 S t = s; // sets t.a to 3, S.opCall(s) is not called

 which does not compile (Error: cannot implicitly convert 
 expression (3)
 of type int to S).

 What is wrong here? Docs or behavior? Tested it on 
 asm.dlang.org where
 it fails with all compiler versions.

 The docs are not clear: s and t are not meant to be 
 module-scope variables, which should be initialized in a 
 'static this()' (or 'shared static this()'). Put them inside a 
 function like main() and it works fine.

I think that's not what the OP means. The documentation is indeed 
saying that a struct with static opCall() can be used to 
_construct_ the structure, with exactly this syntax, i.e. not 
with `S a = S(3);`, but with `S a = 3;`. I, too, find this very 
surprising. opCall() is not a constructor...

"Dicebot" <public dicebot.lv> writes:

On Sunday, 19 July 2015 at 10:26:04 UTC, TC wrote:
 What is wrong here? Docs or behavior? Tested it on 
 asm.dlang.org where it fails with all compiler versions.

Docs are wrong here. `static opCall` was never intended to be 
used as constructor and I consider it a bad style in general. 
This is simply a workaround that people unhappy with lack of 
default struct constructor used but language actively resists 
such misusage (`auto s = new S(42)` won't work too btw) and it 
only causes confusion.