I can understand how to correctly define an instance of BinaryHeap in my class DijkstraWalker at

https://github.com/nordlow/justd/blob/master/knet/traversal.d#L264

because the comparsion function can't ge access to the class member distMap

I get the error

need 'this' for 'distMap' of type 'Tuple!(double, Ref!(Node))[Ref!(Node)]'

What to do?

On Thursday, 19 February 2015 at 11:56:19 UTC, Nordlöw wrote:
> I can understand how to correctly define an instance of BinaryHeap in my class DijkstraWalker at
>
> https://github.com/nordlow/justd/blob/master/knet/traversal.d#L264
>
> because the comparsion function can't ge access to the class member distMap
>
> I get the error
>
> need 'this' for 'distMap' of type 'Tuple!(double, Ref!(Node))[Ref!(Node)]'
>
> What to do?

I don't know if the lambda form can access the outer scope. Try different forms for the comparer:

auto comparer = delegate (a, b)
{
	return this.distMap[a][0] < this.distMap[b][0];
}

BinaryHeap!(Nds, comparer) pendingNds;

or

BinaryHeap!(Nds, "this.distMap[a][0] < this.distMap[b][0]") pendingNds;

Caveat: this is off the top of my head and no way even tested or read the docs. :)

On Thursday, 19 February 2015 at 11:56:19 UTC, Nordlöw wrote:

Please provide reduced examples.

This fails:

class C
{
    int[] a;
    alias BH = BinaryHeap!(int[], (x, y) => (x+a < y));
}

This works:

class C
{
    int[] a;

    void foo() {
        alias BH = BinaryHeap!(int[], (x, y) => (x+a < y));
    }
}

But will create an instance of BinaryHeap per member function.

> What to do?

Dunno.

On Thursday, 19 February 2015 at 14:12:51 UTC, Tobias Pankrath wrote:
> On Thursday, 19 February 2015 at 11:56:19 UTC, Nordlöw wrote:
>
> Please provide reduced examples.
>
> This fails:
>
> class C
> {
>     int[] a;
>     alias BH = BinaryHeap!(int[], (x, y) => (x+a < y));
> }
>
> This works:
>
> class C
> {
>     int[] a;
>
>     void foo() {
>         alias BH = BinaryHeap!(int[], (x, y) => (x+a < y));
>     }
> }
>
> But will create an instance of BinaryHeap per member function.
>
>> What to do?
>
> Dunno.

I modified my algorithm to be more like

http://rosettacode.org/wiki/Dijkstra%27s_algorithm#D

which doesn't require a special comparison function for RedBlackTree.

See update at:

https://github.com/nordlow/justd/blob/master/knet/traversal.d#L108

Thanks anyway.