Re: Problem Instantiating a BinaryHeap with a Comparison Function the needs this

[Gary Willoughby via Digitalmars-d-learn]

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. :)