spreadsort() should work out-of-the-box for std::wstring about sort HOT 6 CLOSED

Done. It wasn't as simple to implement as you suggested, as string_sort requires an unsigned wchar_t, but it works now by splitting the wrapper into 2 enable_ifs, each with its own unsigned character type (wchar_t is signed).

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Ok, I didn't know about the unsigned wchar_t. To be honest, the library I am writing is 90% indirection & code architecture and 10% actual sorting logic if we exclude the algorithms that I didn't write, so I don't understand how some of the algorithms work (including this one), hence the bad suggestion, sorry for that.

Anyway, I didn't have many tests for std::wstring but they are passing with this fix. Thanks :)

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You're welcome.

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Oops, seems that I spoke too soon. For some reason I totally missed a warning introduced by the fix:

With g++:

warning: long, short, signed or unsigned used invalidly for 'unused' [-Wpedantic]

With clang++:

warning: 'wchar_t' cannot be signed or unsigned [-Wpedantic]

It seems like wchar_t shouldn't be declared unsigned, and it's true that its signedness is undefined by the standard. Would std::make_unsigned<wchar_t>::type (or a Boost equivalent) solve the problem?

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On Sun, Sep 20, 2015 at 8:06 AM Morwenn [email protected] wrote:

Oops, seems that I spoke too soon. For some reason I totally missed a
warning introduced by the fix:

With g++:

warning: long, short, signed or unsigned used invalidly for 'unused'
[-Wpedantic]

With clang++:

warning: 'wchar_t' cannot be signed or unsigned [-Wpedantic]

It seems like wchar_t shouldn't be declared unsigned, and it's true that
its signedness is undefined by the standard. Would
std::make_unsigned<wchar_t>::type (or a Boost equivalent) solve the
problem?

While resolving this issue, I ran into another complication I'd forgotten
about: wchar_t is 2 bytes on Windows, and 4 bytes on linux. 2 bytes sorts
nicely with the string_sort approach, but 4 bytes requires breaking up the
characters into pieces and feeding them to the algorithm, a bit of
complication I'm not ready to stick into the core library. Internally
string_sort handles characters of over 2 bytes that aren't being managed by
custom functors by just falling back to std::sort and issuing a
compile-time warning.

So my solution was:
Enable spreadsort for 2-byte wstrings (using uint16_t as the unsigned
character type), and update the documentation to make it clear that it
doesn't work for 4-byte wstrings. I've rolled this change out to master,
and reverted my wstring testing change, as testing std::sort of wstring
vectors on linux is just silly.

Bottom line: sorting wstrings with spreadsort on linux just isn't going to
work for you unless you're willing to write your own functors. For your
application, I think just skipping spreadsort wstring support should be
fine.

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Ok, I think I understand the problem a bit better, thanks for the explanation. I guess I'll just skip the std::wstring support for now as you suggest, or SFINAE it out when the character width is greater than 2 bytes.

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