Range Redesign: Empty Ranges

[Paul Backus]

On Monday, 4 March 2024 at 21:29:40 UTC, Jonathan M Davis wrote:
> 2. The range API provides no way (other than fully iterating 
> through a range) to get an empty range of the same type from a 
> range unless the range is a random-access range.

Genuine question: what are the use-cases for this?

In general, the capabilities of ranges are designed to serve the 
needs of algorithms. Input ranges exist because single-pass 
iteration is all that's needed to implement algorithms like map, 
filter, and reduce. Random-access ranges exist because they're 
needed for sorting algorithms. And so on.

I'm not aware of any algorithm, or class of algorithm, that needs 
this specific capability you're describing. If such algorithms 
exist, we should be using them to guide our design here. If they 
don't...then maybe this isn't really a problem at all.