21.04.2021 16:19, Alain De Vos пишет:
> import std.stdio;
> void main(){
>      struct List {
>          struct Node {
>              float f;
>              Node *next;
>              }
>          Node * root=null;
>          bool empty() const {return !root;}
>          void popFront() {root=root.next;}
>          float front() const {return root.f;}
>          void push(float f) {
>                  Node * newnode=new Node();
>                  newnode.f=f;
>                  root.next=newnode; // Segmentation fault
>                  }
>      }
>      List * l=new List();
>      l.push(3);
>      foreach(element;l){ // Invalid foreach aggregate
>        writeln(element.root.f);
>      }
> }

```D
import std.stdio;
void main(){
    struct List {
        struct Node {
            float f;
            Node *next;
            }
        Node * root=null;
        bool empty() const {return !root;}
        void popFront() {root=root.next;}
        float front() const {return root.f;}
        void push(float f) {
                Node * newnode=new Node();
                newnode.f=f;
            	if (root) // by default root is null so you need to initialize it first time
                	root.next=newnode;
            	else
                    root = newnode;
                }
    }
    List * l=new List();
    l.push(3);
    foreach(element; *l){ // Invalid foreach aggregate because `l` is a pointer to List, so you need to dereference the pointer
      writeln(element);
    }
}
```

1) you need to initialize the root
2) pointer to range is not valid foreach aggregate

Here a working code,
```
import std.stdio;
void main(){
    struct List {
        struct Node {
            float f;
            Node *next=null;
            }
        Node * root=null;
        bool empty() const {return !root;}
        void popFront() {root=root.next;}
        float front() const {return root.f;}
        void pushfront(float f) {
				Node * newnode=new Node();
                newnode.f=f;
				newnode.next=root;
				root=newnode;
               }
		void pushend(float f){
                Node * newnode=new Node();
                newnode.f=f;
                Node *t=root;
                if(t==null)
					{t=newnode;}
				else{
					while(t!=null && t.next!=null)
						{t=t.next;}
					t.next=newnode;
					}
			}
		void printall(){
			Node *l=root;
			for( ; l ; l=l.next){
				writeln(l.f);
			}
		}
    }
    List * l=new List();
    l.pushfront(2);
    l.pushfront(1);
    l.pushend(3);
    l.pushend(4);
    foreach(element; *l) writeln(element);
    (*l).printall();

```