Feature/basic string

[yamasdais]

Hello,

I wanted to use hana::wstring but couldn't find. So, I tried to make it.
Could you please check it out?

• Added hana::basic_string
• Added hana::wstring as hana::basic_string<wchar_t>
• Added tests for hana::basic_string<> and hana::wstring.

EDIT: 2019-03-12
I have tried various work around to pass the Travis test for clang 3.5, but it can't.
/home/travis/build/yamasdais/hana/include/boost/hana/basic_string.hpp:116:20: error: no matching function for call to 'prepare_impl'
return prepare_impl<CastChar<CharTo, CharFrom>>(
/home/travis/build/yamasdais/hana/include/boost/hana/basic_string.hpp:108:9: note: candidate template ignored: substitution failure [with Cast = boost::hana::basic_string_detail::CastChar<wchar_t, wchar_t>, S = tmp, N = <0, 1, 2, 3>]: non-type template argument is not a constant expression
prepare_impl(S, std::integer_sequence<std::size_t, N...>)

If anyone has a good idea, please help me.

Regards,

[ricejasonf]

Hi. It looks like you need to rebase onto the develop branch. Also commits should be squashed into a single commit (Item 5 in https://github.com/boostorg/hana/blob/master/CONTRIBUTING.md)

[yamasdais]

Hi. Thank you for the comment.
I'll give it a try

[yamasdais]

I renewed the branch from the 'develop branch' a single commit.

Regards,

[ricejasonf]

Try this:

1. Make a new branch off of the latest develop @ 4536973
2. Add your commit
   • git cherry-pick 70038edbee2fe877caf051352d6b92e75279d7d3
3. Force push to your original branch on the remote
   • git push --force <remote> <new branch>:feature/basic_string

I did not try step 3 myself, but it should update this PR to have only your commit.

EDIT: FWIW I don't know how much of an issue the weird commits are, and I am not the one who will accept the PR anyways.

[yamasdais]

I learned git operations I have never used these few days 😃

$ git checkout -b feature/basic_string_pr1 upstream/develop
$ git log --oneline | head -1
4536973 [Travis] Fix build with Clang 7
$ git cherry-pick 70038edbee2fe877caf051352d6b92e75279d7d3
$ git push --force origin feature/basic_string_pr1:feature/basic_string

It seems a `clean' commit you might expected.
Thank you for the advice, anyway.