Re: Transparent cast from class to member pointer?

2019-04-15 Thread Alex via Digitalmars-d-learn 

On Monday, 15 April 2019 at 15:07:10 UTC, Robert M. Münch wrote:

On 2019-04-15 08:19:57 +, Ali ‡ehreli

Bingo, I didn't know that I can do an 'alias this' using a 
function and not only a type... pretty cool. So, with several 
of these I can setup implicit conversions to different types. 
Thanks.


Well, as I know, multiple alias this won't work yet...
https://wiki.dlang.org/DIP66

Re: Transparent cast from class to member pointer?

2019-04-15 Thread Robert M. Münch via Digitalmars-d-learn 

On 2019-04-15 08:19:57 +, Ali ‡ehreli said:


'alias this' can do that:


Hi, I had the suspicion already...


struct IM;
struct C {
  IM *impl;
};

int cInit(C* self) {
   return 0;
}

class I {
 C handler;

 this(){cInit();}

   C* ptr() {   // <== ADDED
 return 
   }

   alias ptr this;  // <== ADDED
}

void someFunc(C* self) {
}

void main() {
   I myI = new I();
   someFunc(myI);
}


Bingo, I didn't know that I can do an 'alias this' using a function and 
not only a type... pretty cool. So, with several of these I can setup 
implicit conversions to different types. Thanks.


--
Robert M. Münch
http://www.saphirion.com
smarter | better | faster

Re: Transparent cast from class to member pointer?

2019-04-15 Thread diniz via Digitalmars-d-learn 

Le 15/04/2019 à 08:30, Robert M. Münch via Digitalmars-d-learn a écrit :
The C side requires that *impl is the 1st member in the struct/class whereever 
it is stored. Hence, the wrapping in a struct and not directly putting it into a 
D class.


All right! Did not think at this usage case, interfacing with C.

--
diniz {la vita e estranj}

Re: Transparent cast from class to member pointer?

2019-04-15 Thread Ali Çehreli via Digitalmars-d-learn 

On 04/14/2019 11:03 AM, Robert M. Münch wrote:

struct IM;
struct C {
  IM *impl;
};

int cInit(C* self);

class I {
 C handler;

 this(){cInit();}
}

Is there a simple way that I can use handler without the address-of 
operator and automatically get *impl?


Something like:

class I {
 C handler;

 this(){cInit(handler);}
}

And later can use I in a way like this without having to define/write 
explicit casts everywhere?


someFunc(C* self);

I myI;
someFunc(myI);




'alias this' can do that:

struct IM;
struct C {
 IM *impl;
};

int cInit(C* self) {
  return 0;
}

class I {
C handler;

this(){cInit();}

  C* ptr() {   // <== ADDED
return 
  }

  alias ptr this;  // <== ADDED
}

void someFunc(C* self) {
}

void main() {
  I myI = new I();
  someFunc(myI);
}

Ali

Re: Transparent cast from class to member pointer?

2019-04-15 Thread Robert M. Münch via Digitalmars-d-learn 

On 2019-04-14 20:01:27 +, diniz said:


Le 14/04/2019 à 20:03, Robert M. Münch via Digitalmars-d-learn a écrit :

struct IM;
struct C {
 IM *impl;
};

int cInit(C* self);

class I {
C handler;

this(){cInit();}
}

Is there a simple way that I can use handler without the address-of 
operator and automatically get *impl?


Something like:

class I {
C handler;

this(){cInit(handler);}
}

And later can use I in a way like this without having to define/write 
explicit casts everywhere?


someFunc(C* self);

I myI;
someFunc(myI);


Do you have a clear and correct view of what you want to express, of 
the application? How does it look (for us), if you replace IM, C, impl, 
cInit, I, handler, with meaningful (and correctly chosen) terms?


Well, ok... even it really doesn't matter a lot.

IM = Implementaiton Context (C-API)
C  = Core Context (C-API)
I  = Implementation D Class

The C side requires that *impl is the 1st member in the struct/class 
whereever it is stored. Hence, the wrapping in a struct and not 
directly putting it into a D class.


--
Robert M. Münch
http://www.saphirion.com
smarter | better | faster

Re: Transparent cast from class to member pointer?

2019-04-14 Thread diniz via Digitalmars-d-learn 

Le 14/04/2019 à 20:03, Robert M. Münch via Digitalmars-d-learn a écrit :

struct IM;
struct C {
  IM *impl;
};

int cInit(C* self);

class I {
 C handler;

 this(){cInit();}
}

Is there a simple way that I can use handler without the address-of operator and 
automatically get *impl?


Something like:

class I {
 C handler;

 this(){cInit(handler);}
}

And later can use I in a way like this without having to define/write explicit 
casts everywhere?


someFunc(C* self);

I myI;
someFunc(myI);


Do you have a clear and correct view of what you want to express, of the 
application? How does it look (for us), if you replace IM, C, impl, cInit, I, 
handler, with meaningful (and correctly chosen) terms?


--
diniz {la vita e estranj}