Add string_view operator<< support

[kevgs]

Right now std::cout << gsl::cstring_view("asdf") doesn't print "asdf". This feature is missing. Something like this would be very useful http://en.cppreference.com/w/cpp/experimental/basic_string_view/operator_ltlt

[neilmacintosh]

Agreed Eugene Kosov (@kevgs). In the near future, I'm going to rework string_view (now string_span) to be its own type (rather than a type alias). When that change goes in then I'll add an output operator. I don't want to do so with the present implementation as it will be the output operator for any array_view (now span) of const char, which may not always be desirable.

[kevgs]

Sounds great!

Here is the code is use for a workaround. Maybe it could help someone https://gist.github.com/kevgs/8a5ed24168ea703c3d32

[MikeGitb]

Neil MacIntosh (@neilmacintosh): Is there any update on this? I think gsl::[c][z]string_span could really use an overloaded operator<<.
Unfortunately I don't see a simple way to simulate the exact behavior of operator<<(ostream&, const string&) (a formatted output) for the non-zero terminated versions, but in many cases an unformatted output (via ostream.write) could be good enough anyway.

[biocomp]

Neil MacIntosh (@neilmacintosh) - updates on the issue? :)

[neilmacintosh]

Artem Tokmakov (@biocomp) I'd be happy to look at a PR to add operator<<, but I haven't had time to make any updates to string_span lately.

[PeeyushRawat]

i want to give a try.

[JordanMaples]

Maintainer's call: Sorry for the delayed reply. gsl::string_view has been standardized as std::string_view which has a standard interface now. So that supersedes this issue.

Additionally: gsl::string_span has been removed from the C++ Core Guidelines with isocpp/CppCoreGuidelines#1680.

Remove string_span, recommend using std::string_view, std:::span,<char> or gsl::span<char> instead