Polymorphic recursive class

[Jack Applegame via Digitalmars-d]

On Monday, 13 July 2015 at 13:51:51 UTC, Dmitry Olshansky wrote:
> You can do it no problem, it just requires to manually 
> implement boxing and make `right` a template that casts to the 
> right type. The reason is that D doesn't provide an extra 
> abstraction layer that is "auto-magically" there in typical FP 
> language.
>
> Not tested but this should work:
>
> class Nested(T){
> 	T left;
> 	void* right_; // or use opaque type if allergic to void*
> 	@property auto right()(){ // empty template to prevent 
> recursion
> 		return cast(Nested!(T[])right_;
> 	}
> 	@property auto right(U)(Nested!U type){ // empty template to 
> prevent recursion
> 		right_ =  cast(void*)right_;
> 	}
> 	
> 	// and lastly the constructor should be templated
> 	this(U)(T l, Nested!(U) r) {
>    	 left = l;
>    	 right = r;
>   	}
> }

Wow! Template properties is nice idea. Thanks.