Comparing strings fussballmanager and fußballmanager in C++

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In SQL, you can compare successfully two strings depending on the collation
With Latin1_General_CI_AS, fussballmanager and fußballmanager are considered equal.

They are different with SQL_Latin1_General_CP1_CI_AS.

I am trying to replicate the same behaviour in C++. I understand it's dependent on the locale and I would like to have some code where the user can decide which locale to use.

What I have tried:

STL

std::locale loc1("german");

wstring a("fussballmanager");
wstring b("fußballmanager");

const std::collate<wchar_t>& coll = use_facet<std::collate<wchar_t> >(loc1);
int nRes = coll.compare(a.data(), a.data() + a.size(),
                        b.data(), b.data()  + b.size());
// => nRes is 1 not 0

BOOST

boost::locale::generator gen;
std::locale loc = gen("en-GB");
std::locale::global(loc);


wstring a("fussballmanager");
wstring b("fußballmanager");
int nRes = use_facet<boost::locale::collator<wchar_t> >(loc).compare(boost::locale::collator_base::primary, a, b);
// Crash here (it works if I leave the locale string empty: replace en-GB by ""

Posted 25-Nov-16 1:19am

BadJerry

Updated 25-Nov-16 2:48am

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BadJerry 25-Nov-16 10:46am

OK if you write the following (add ut8) - no crash in Boost!

std::locale loc = gen("en-GB.UTF-8");

Jochen's solutions probably means no need for boost for others ( I already had it)

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Jochen Arndt · Accepted Answer · 2016-11-25T02:48:00

There is a really good answer about string comparison at this SO thread:
c++ - How to compare a "basic_string" using an arbitary locale - Stack Overflow[^].

Regarding your SQL examples, both should return false for the example strings when using AS (Accent Sensitive). But I'm not quite sure about the special case Eszett. The only difference is CP1 which selects code page 1252 while the other uses a default code page (which might be 1252 too).

I have not used the boost collating and comparing functions so far and can't therefore give a solution using them.

If you are on Windows, you can use the CompareStringEx function (Windows)[^].

There is also the ICU - International Components for Unicode[^] project providing a library that supports collated comparing (see Collation - ICU User Guide[^]).