Re: Template delegate/function ptr struct member

[uri via Digitalmars-d-learn]

On Tuesday, 13 May 2014 at 07:50:09 UTC, Rikki Cattermole wrote:

On 13/05/2014 7:28 p.m., ed wrote:
I'm porting some C++ code to D and a struct has the following 
member:


struct S
{
// ...
 //void* (*createMethod)();

void* function() createMethod;

}

I'd like to extend this as little to accept delegates for 
future use

without breakage to existing code...

Is it possible to template this so "createMethod" can be a 
delegate() or
function() of any type *and* have the compiler infer the type 
from ctor

parameters?

For example:
---
struct S(F)
{
// ...
F createMethod;
this(alias F)() {createMethod = &F;}
}
static void* func() {return null;}

void main() {
auto s1 = S(&func);
auto s2 = S(&Object.classinfo.create);

// s1 is S!(void* function())
// s2 is S!(Object delegate() const);
}
---

Is this a good idea or am I way off?

Thanks,
ed


I would recommend going the route of property functions and 
using delegates as the default.


alias createMethodDel = void* delegate();
alias createMethodFunc = void* function();

struct S {
private createMethodDel createMethod_;

@property {
createMethodDel createMethod() {
return createMethod_;
}

void createMethod(createMethodDel func) {
createMethod_ = func;
}

void createMethod(createMethodFunc func) {
import std.functional : toDelegate;
createMethod_ = toDelegate(func);
}
}
}

That way you know what you have access to is always callable 
and won't break any code.


I was so focused on a template solution that I never even thought 
of doing it that way, nice one :)



Thanks,
ed

Re: Template delegate/function ptr struct member

[Rikki Cattermole via Digitalmars-d-learn]

On 13/05/2014 7:28 p.m., ed wrote:

I'm porting some C++ code to D and a struct has the following member:

struct S
{
// ...
  //void* (*createMethod)();

void* function() createMethod;

}

I'd like to extend this as little to accept delegates for future use
without breakage to existing code...

Is it possible to template this so "createMethod" can be a delegate() or
function() of any type *and* have the compiler infer the type from ctor
parameters?

For example:
---
struct S(F)
{
 // ...
 F createMethod;
 this(alias F)() {createMethod = &F;}
}
static void* func() {return null;}

void main() {
 auto s1 = S(&func);
 auto s2 = S(&Object.classinfo.create);

 // s1 is S!(void* function())
 // s2 is S!(Object delegate() const);
}
---

Is this a good idea or am I way off?

Thanks,
ed


I would recommend going the route of property functions and using 
delegates as the default.


alias createMethodDel = void* delegate();
alias createMethodFunc = void* function();

struct S {
private createMethodDel createMethod_;

@property {
createMethodDel createMethod() {
return createMethod_;
}

void createMethod(createMethodDel func) {
createMethod_ = func;
}

void createMethod(createMethodFunc func) {
import std.functional : toDelegate;
createMethod_ = toDelegate(func);
}
}
}

That way you know what you have access to is always callable and won't 
break any code.

Template delegate/function ptr struct member

[ed via Digitalmars-d-learn]

I'm porting some C++ code to D and a struct has the following 
member:


struct S
{
// ...
 //void* (*createMethod)();

void* function() createMethod;

}

I'd like to extend this as little to accept delegates for future 
use without breakage to existing code...


Is it possible to template this so "createMethod" can be a 
delegate() or function() of any type *and* have the compiler 
infer the type from ctor parameters?


For example:
---
struct S(F)
{
// ...
F createMethod;
this(alias F)() {createMethod = &F;}
}
static void* func() {return null;}

void main() {
auto s1 = S(&func);
auto s2 = S(&Object.classinfo.create);

// s1 is S!(void* function())
// s2 is S!(Object delegate() const);
}
---

Is this a good idea or am I way off?

Thanks,
ed