[oneDPL] Create a subsection for is_execution_policy type trait

[akukanov]

This PR describes oneDPL is_execution_policy trait in more detail, and also addresses #558.

[danhoeflinger]

Generally LGTM, optional comment about the decay note.

[danhoeflinger]

LGTM

[rarutyun]

Overall, looks good to me. I left some small comments that do look as improvements to me. But you might disagree

[rarutyun]

Suggested change

	to the same class template. It is unspecified in which namespace the underlying class template and its specializations
	are defined.
	to the same class template. It is unspecified, which namespace the underlying class template and its specializations
	are defined in.

[akukanov]

Spellcheckers do not complain :), so I will keep this intact.

[rarutyun]

Sure, this is small suggestion. As far as I understand "preposition + which" is consider to be poorer English. More common use is "bla-bla, which + <proposition at the end>. Again, not proposing to change that but for my curiosity we could summon a native speaker. @danhoeflinger, could you please share your opinion?

[akukanov]

I searched for clarification on this, and I have found that "preposition + which" is considered not poorer but more formal English.

[danhoeflinger]

I agree that "in which" is more formal (but a bit awkward), and "which ... in" is less formal, and a "dangling preposition" https://www.thefreedictionary.com/Dangling-Prepositions.htm which is a classic English grammar issue.

I was trying to rephrase to avoid the problem, but I think it may make it less clear.

"The location of the underlying class template definition and its specializations is left unspecified."

[danhoeflinger]

Another option, avoiding the preposition:
"It is unspecified, which namespace contains the underlying class template definition and its specializations."

[akukanov]

Thanks Dan, I like the last suggestion, will apply it.

[rarutyun]

"It is unspecified, which namespace contains the underlying class template definition and its specializations."

I also like that.

... not poorer but more formal English.

Thanks for clarification

[rarutyun]

Sure, this is small suggestion. As far as I understand "preposition + which" is consider to be poorer English. More common use is "bla-bla, which + <proposition at the end>. Again, not proposing to change that but for my curiosity we could summon a native speaker. @danhoeflinger, could you please share your opinion?

[rarutyun]

Suggested change

	constexpr inline bool is_execution_policy_v = oneapi::dpl::is_execution_policy<T>::value;
	inline constexpr bool is_execution_policy_v = oneapi::dpl::is_execution_policy<T>::value;

I prefer that order because this is the way it's defined in C++ standard. I don't want to hold this PR because of that issue but if you decide to change it the way I am suggesting, please ping me and I approve this patch once again.

[akukanov]

No problem, I will do it. No re-approval is needed, thanks.