It has a similar rationale as the starts_with/ends_with paper, which doesn't mention the performance benefit and was accepted.
Performance shouldn't be the only benchmark to extend the standard I think.
Improving code readability and teachability for beginners and people coming from other languages is also a good rationale to extend the standard.
On 27/05/2019 14.30, Wim Leflere via Std-Proposals wrote:
> After seeing that 'starts_with' and 'ends_with' were added to std::string
> in C++20 (P0457), I was wondering why 'contains' was still missing as a
> std::string member function.
> So I wrote a proposal (starting from P0457) to add it.
> Please find the draft of the proposal here:
> I am looking forward to your valuable comments.
The rationale vs. string::find is... weak. Both starts_with and
ends_with have a clear performance benefit in addition to improved
semantics. Even for <container>::contains (vs. count) that is the case.
For string::contains, this isn't the case; the rationale is *purely*
Mind, I like consistent, easy to use API's, but I wouldn't hold your