Re: [boost] Painting a bikeshed ...

Subject: Re: [boost] Painting a bikeshed ...
From: Rob Stewart (rob.stewart_at_[hidden])
Date: 2015-10-02 04:55:09

On October 1, 2015 10:29:57 PM EDT, Gottlob Frege <gottlobfrege_at_[hidden]> wrote:
> 
> 'range' is wrong and shouldn't be used, unless somehow qualified.
> The things passed in are ranges, pairs of iterators are ranges, but
> sort_subrange is using 'range' to mean the after-the-fact range. ie
> the
> range that would be there after sorting. Yes it turns out to be the
> same iterators, but it's confusing.

I had begun a reply with similar complaints, but never finished it, so I'll jump on your bandwagon instead.

I, too, found the naming confusing. I find the interface really odd, too. I've never seen an algorithm that uses an iterator range that refers to a portion of an as-if-sorted range. I suppose there are real use cases or Sean wouldn't have worked on the algorithm he presented, but it's still an odd interface.

> I would think sort_subrange would only
> sort
> the elements within the subrange (verb object - sort subrange) not
> sort
> things from the total range _into_ the subrange.

Right

> So 'into' (or similar) might help.  ie sort_into_subrange for the
> first one. (just as a starting idea)

That's better, but it still fails to capture the behavior well. The algorithm acts as if the entire range is sorted, providing a view into a subrange that is actually sorted. Perhaps "view" should be in the name: view_sorted_subrange?

> The second could be gather_into_subrange.  Leaves you wondering what
> criteria is used to select the gathering, but you'll check the docs
> instead
> guessing incorrectly.

I also think "gather" should be part of the name of the second algorithm.

> (NOT understanding is better than
> MISunderstanding
> when it comes to names)

Indeed

> I do like gather.  And the association with nth element.

The problem with nth_element is that no index is given, but that algorithm is already established, so building on that name could help. However, nth_element also specifies the order of the elements to the left and right of the nth.

> To be clear, the leftover elements on the left and right aren't even
> partitioned? ie elements on the left could be greater than some
> elements on the right?

If that were specified, then the mth_to_nth_element name has merit for Sean's algorithm, but Marshall's is still left without a good name. Finding similar names that vary only on the use of "sort" vs. "gather", for example, would be helpful.

___
Rob

(Sent from my portable computation engine with which I am not forced to top post)