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- //
- // Copyright (c) 2009-2011 Artyom Beilis (Tonkikh)
- //
- // Distributed under the Boost Software License, Version 1.0. (See
- // accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt)
- //
- // vim: tabstop=4 expandtab shiftwidth=4 softtabstop=4 filetype=cpp.doxygen
- /*!
- \page conversions Text Conversions
- There is a set of functions that perform basic string conversion operations:
- upper, lower and \ref term_title_case "title case" conversions, \ref term_case_folding "case folding"
- and Unicode \ref term_normalization "normalization". These are \ref boost::locale::to_upper "to_upper" , \ref boost::locale::to_lower "to_lower", \ref boost::locale::to_title "to_title", \ref boost::locale::fold_case "fold_case" and \ref boost::locale::normalize "normalize".
- All these functions receive an \c std::locale object as parameter or use a global locale by default.
- Global locale is used in all examples below.
- \section conversions_case Case Handing
- For example:
- \code
- std::string grussen = "grüßEN";
- std::cout <<"Upper "<< boost::locale::to_upper(grussen) << std::endl
- <<"Lower "<< boost::locale::to_lower(grussen) << std::endl
- <<"Title "<< boost::locale::to_title(grussen) << std::endl
- <<"Fold "<< boost::locale::fold_case(grussen) << std::endl;
- \endcode
- Would print:
- \verbatim
- Upper GRÜSSEN
- Lower grüßen
- Title Grüßen
- Fold grüssen
- \endverbatim
- You may notice that there are existing functions \c to_upper and \c to_lower in the Boost.StringAlgo library.
- The difference is that these function operate over an entire string instead of performing incorrect character-by-character conversions.
- For example:
- \code
- std::wstring grussen = L"grüßen";
- std::wcout << boost::algorithm::to_upper_copy(grussen) << " " << boost::locale::to_upper(grussen) << std::endl;
- \endcode
- Would give in output:
- \verbatim
- GRÜßEN GRÜSSEN
- \endverbatim
- Where a letter "ß" was not converted correctly to double-S in first case because of a limitation of \c std::ctype facet.
- This is even more problematic in case of UTF-8 encodings where non US-ASCII are not converted at all.
- For example, this code
- \code
- std::string grussen = "grüßen";
- std::cout << boost::algorithm::to_upper_copy(grussen) << " " << boost::locale::to_upper(grussen) << std::endl;
- \endcode
- Would modify ASCII characters only
- \verbatim
- GRüßEN GRÜSSEN
- \endverbatim
- \section conversions_normalization Unicode Normalization
- Unicode normalization is the process of converting strings to a standard form, suitable for text processing and
- comparison. For example, character "ü" can be represented by a single code point or a combination of the character "u" and the
- diaeresis "¨". Normalization is an important part of Unicode text processing.
- Unicode defines four normalization forms. Each specific form is selected by a flag passed
- to \ref boost::locale::normalize() "normalize" function:
- - NFD - Canonical decomposition - boost::locale::norm_nfd
- - NFC - Canonical decomposition followed by canonical composition - boost::locale::norm_nfc or boost::locale::norm_default
- - NFKD - Compatibility decomposition - boost::locale::norm_nfkd
- - NFKC - Compatibility decomposition followed by canonical composition - boost::locale::norm_nfkc
- For more details on normalization forms, read <a href="http://unicode.org/reports/tr15/#Norm_Forms">this article</a>.
- \section conversions_notes Notes
- - \ref boost::locale::normalize() "normalize" operates only on Unicode-encoded strings, i.e.: UTF-8, UTF-16 and UTF-32 depending on the
- character width. So be careful when using non-UTF encodings as they may be treated incorrectly.
- - \ref boost::locale::fold_case() "fold_case" is generally a locale-independent operation, but it receives a locale as a parameter to
- determine the 8-bit encoding.
- - All of these functions can work with an STL string, a NUL terminated string, or a range defined by two pointers. They always
- return a newly created STL string.
- - The length of the string may change, see the above example.
- */
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