Linked list, printing looks destructive.

[cc]

On Monday, 25 April 2022 at 01:40:01 UTC, Alain De Vod wrote:
> Following program is a single linked list.
> We expect as output 1 2 3 1 2 3
> But the output is only 1 2 3
> ```

If you don't need List to be treated as a true range, but just 
want to iterate, a simple way to do this is with opApply:
https://tour.dlang.org/tour/en/gems/opdispatch-opapply
```d
import std.stdio: write,writeln;
import std.range: empty,popFront,front;

struct Node {
	int element;
	Node * next;
}

class List {
	Node * root=null;
	this(int[] AR){foreach(i ; AR)pushfront(i);}
	bool empty() const {return !root;}
	/*void popFront() {root=root.next;}
	float front() const {return root.element;}*/
	void pushfront(int element) {
		Node * newnode=new Node();
		newnode.element=element;
		newnode.next=root;
		root=newnode;
	}
	int opApply(int delegate(typeof(Node.element)) dg) {
		Node* current = root;
		while (current) {
			if (dg(current.element)) return 1; // stop iteration if the 
foreach body asks to break
			current = current.next;
		}
		return 0;
	}
}//List

void main(){
	List l=new List([3,2,1]);
	foreach(element; l) writeln(element);
	foreach(element; l) writeln(element);
}

// 1 2 3 1 2 3
```