Big Oversight with readln?

[Mike Parker via Digitalmars-d-learn]

On Friday, 24 February 2017 at 04:22:17 UTC, Jonathan Marler 
wrote:

>
> I discovered the .capacity property of arrays.  I don't know 
> why I've never seen this but it looks like this is how readln 
> is recovering this seemingly lost peice of data.  This does 
> have an odd consequence though, if you pass a slice into readln 
> it will read past the end of it if the underlying buffer is 
> larger.  This might be something worth adding to the 
> documentation.
>
> Also I'm not completely sure how .capacity works, I assume it 
> has to look up this information in the memory management 
> metadata.  Any enlightenment on this subject is appreciated. It 
> also says it's a O(log(n)) operation so I'm guessing it's 
> looking it up in some sort of binary tree data structure.

https://dlang.org/phobos/object.html#.capacity