Virtual templates members

[Nicolas Sicard]

On Thursday, 8 August 2013 at 01:48:49 UTC, JS wrote:
> The following code is used to reduce dependence on new and the 
> GC. iNew is used as the replacement.
>
> The problem is, where ever New is used, it requires typing the 
> type twice.
>
> e.g.,
>
> A.New!A(...)
>
> instead of A.New(...)
>
> Is there any way to solve this issue?
>
> (iNew is suppose to provide the contract to implement a "new" 
> like method that will allocate the class. Note there is no 
> virtual function so no overhead)
>
>
> import std.stdio, std.conv;
>
> enum eNew
> {
> 	Default = 0,
> }
>
> interface iNew
> {
>
> 	final static T New(T, A...)(A args)
> 	{
> 		eNew type = eNew.Default;
> 		static if (A.length == 0 || !is(typeof(args[0]) == eNew))
> 			alias nargs = args;
> 		else
> 		{
> 			type = cast(eNew)args[0];
> 			alias nargs = args[1..$];
> 		}
>
> 		writeln(">> ",  __traits(classInstanceSize, T));
>
> 		switch (type)
> 		{	
> 			default: return new T(nargs);
> 		}
> 		
> 		return new T(nargs);
> 	}
> }
>
> class A : iNew
> {
> 	int t;
> }
>
> class B : A
> {
> 	int q;
>     double d;
> }
>
> void main()
> {
> 	A a = A.New!A();
> 	B b = B.New!B();
> 	readln();
> }

Why not make it a mixin template?
---
import std.stdio, std.conv;

enum eNew
{
	Default = 0,
}

mixin template iNew(T)
{
	final static T New(A...)(A args)
	{
		eNew type = eNew.Default;
		static if (A.length == 0 || !is(typeof(args[0]) == eNew))
			alias nargs = args;
		else
		{
			type = cast(eNew)args[0];
			alias nargs = args[1..$];
		}
		
		writeln(">> ",  __traits(classInstanceSize, T));
		
		switch (type)
		{	
			default: return new T(nargs);
		}
		
		//return new T(nargs);
	}
}

class A
{
	mixin iNew!A;
	int t;
}

class B : A
{
	mixin iNew!B;
	int q;
	double d;
}

void main()
{
	A a = A.New();
	B b = B.New();
	readln();
}
---