Why after writeln the binaryHeap become empty?

[lili]

On Tuesday, 18 June 2019 at 17:25:51 UTC, Johannes Loher wrote:
> The result of heapify is a BinaryHeap, which is a range. writeln
> basically prints ranges by iterating over them and printing 
> each element
> (except for the types which are special cased, such as dynamic 
> arrays
> etc.). However, ranges are consumed by iterating over them, 
> which
> explains the behavior because writeln is not special cased for 
> BinaryHeaps.
>
> Funnily enough, BinaryHeap does not implement a "save" method, 
> which is the usual way of making ranges copiable, i.e. making 
> them ForwardRanges. In this case I believe save could even 
> simply be an alias to dup.

Do you known reason for why Dlang Range are consumed by iterating 
over them. I this design is strange.