SListRange, Ranges, costructors

[bearophile]

> 1) I've seen that the Node struct inside std.range.SListRange is not a
> static struct, is it a small bug?

Bug 4087. Currently it's not a bug.


> 2) In that List(T) I've used the Range protocol. But I've had to
> add a reset() function too. Isn't it useful for foreach() to call
> a function similar to reset() (if present) at the begin of the
> iteration, to set the variables necessary for the iteration?

I've taken a look at SListRange, and it seems the p pointer is useless, this works, and there is no need for the reset():

import std.stdio;

struct List(T) {
    static struct Node {
        T data;
        Node* next;
        this(T d, Node* p) {
            data = d;
            next = p;
        }
    }

    Node* lh;

    this(T[] arr) {
        foreach_reverse (el; arr)
            lh = new Node(el, lh);
    }

    bool empty() { return !lh; }
    T front() { return lh.data; }
    void popFront() { lh = lh.next; }
}

void main() {
    List!int items = [1, 2, 3];
    foreach (x; items) write(x, " "); // prints 1 2 3
    writeln();
    assert(items.lh);
    foreach (x; items) write(x, " "); // prints 1 2 3
}

But I feel dumb and I don't understand, why isn't lh null at the end of the first foreach?


> 3) The stack initalization of a struct has some built-in sugar,
> while to allocate the struct on the stack you need a this() method:

Enhancement request 4086.

Bye,
bearophile