trying to follow:
http://ddili.org/ders/d.en/class.html

//--- OSX 10.9 DMD 2.065
module test;

class Foo {
     int num;

     this(int num) {
         this.num = num;
     }

     Foo dup() const {
         return new Foo(this.num);
     }

     immutable(Foo) idup() const {
         return new immutable(Foo)(this.num);
     }
}

void main() {
     auto  foo = new Foo(1);
     auto mfoo = foo.dup();
     auto ifoo = foo.idup();
}

* test.d(15): Error: mutable method test.Foo.this is not callable
using a immutable object
* test.d(15): Error: no constructor for Foo
* Failed: ["dmd", "-v", "-o-", "test.d", "-I."]
//---

What am i missing?

On Fri, 16 May 2014 16:28:41 -0400, Joshua Niehus <jm.niehus@gmail.com> wrote:

> trying to follow:
> http://ddili.org/ders/d.en/class.html
>
> //--- OSX 10.9 DMD 2.065
> module test;
>
> class Foo {
>       int num;
>
>       this(int num) {
>           this.num = num;
>       }
>
>       Foo dup() const {
>           return new Foo(this.num);
>       }
>
>       immutable(Foo) idup() const {
>           return new immutable(Foo)(this.num);
>       }
> }
>
> void main() {
>       auto  foo = new Foo(1);
>       auto mfoo = foo.dup();
>       auto ifoo = foo.idup();
> }
>
> * test.d(15): Error: mutable method test.Foo.this is not callable
> using a immutable object
> * test.d(15): Error: no constructor for Foo
> * Failed: ["dmd", "-v", "-o-", "test.d", "-I."]
> //---
>
> What am i missing?

your constructor needs the immutable tag.

this(int num) immutable ...

However, you can avoid much of this by tagging things as pure:

(untested, but just keep the internals the same)

class Foo
{
   int num;
   this(int num) pure {...}
   Foo dup() const pure {...}
   immutable(Foo) idup() const pure {...}
}

void main()
{
   ... // same implementation
}

Note that doing this, you do not need to have an idup, this should work:

immutable ifoo = foo.dup();

-Steve

On 05/16/2014 01:28 PM, Joshua Niehus wrote:

> trying to follow:
> http://ddili.org/ders/d.en/class.html
>
> //--- OSX 10.9 DMD 2.065
> module test;
>
> class Foo {
>       int num;
>
>       this(int num) {
>           this.num = num;
>       }
>
>       Foo dup() const {
>           return new Foo(this.num);
>       }
>
>       immutable(Foo) idup() const {
>           return new immutable(Foo)(this.num);
>       }
> }
>
> void main() {
>       auto  foo = new Foo(1);
>       auto mfoo = foo.dup();
>       auto ifoo = foo.idup();
> }
>
> * test.d(15): Error: mutable method test.Foo.this is not callable
> using a immutable object
> * test.d(15): Error: no constructor for Foo
> * Failed: ["dmd", "-v", "-o-", "test.d", "-I."]
> //---
>
> What am i missing?

My apologies. The code was written for an older version of dmd. The simplest fix is to define the constructor as pure:

     pure this(int num) {
         this.num = num;
     }

Ali

On Fri, 16 May 2014 16:36:36 -0400, Ali Çehreli <acehreli@yahoo.com> wrote:

Beat you by 8 seconds :)

-Steve

On 05/16/2014 01:37 PM, Steven Schveighoffer wrote:
> On Fri, 16 May 2014 16:36:36 -0400, Ali Çehreli <acehreli@yahoo.com> wrote:
>
> Beat you by 8 seconds :)
>
> -Steve

I am happy to be within one minute. :)

Ali

On Friday, 16 May 2014 at 20:36:37 UTC, Ali Çehreli wrote:
>
> My apologies. The code was written for an older version of dmd. The simplest fix is to define the constructor as pure:
>
>      pure this(int num) {
>          this.num = num;
>      }
>
> Ali

Ahh great thanks guys.
No worries Ali, great book, i refer to it all the time :)