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A basic_string is guaranteed to be specializable for any type with a char_traits struct to accompany it. As of C++11, only char, wchar_t, char16_t and char32_t specializations are required to be implemented. [16] A basic_string is also a Standard Library container, and thus the Standard Library algorithms can be applied to the code units in ...
If wchar_t is 32-bits, then 32-bit encodings, such as UTF-32, can be stored. (The standard requires a "type that holds any wide character", which on Windows no longer holds true since the UCS-2 to UTF-16 shift. This was recognized as a defect in the standard and fixed in C++.) [4] C++11 and C11 add two types with explicit widths char16_t and ...
"The width of wchar_t is compiler-specific and can be as small as 8 bits. Consequently, programs that need to be portable across any C or C++ compiler should not use wchar_t for storing Unicode text. The wchar_t type is intended for storing compiler-defined wide characters, which may be Unicode characters in some compilers." [6]
A value greater than \U0000FFFF may be represented by a single wchar_t if the UTF-32 encoding is used, or two if UTF-16 is used. Importantly, the universal character name \u00C0 always denotes the character "À", regardless of what kind of string literal it is used in, or the encoding in use. The octal and hex escape sequences always denote ...
Unicode can also be stored in strings made up of code units that are larger than char. These are called "wide characters". The original C type was called wchar_t. Due to some platforms defining wchar_t as 16 bits and others defining it as 32 bits, recent versions have added char16_t, char32_t.
The C++ Standard Library is based upon conventions introduced by the Standard Template Library (STL), and has been influenced by research in generic programming and developers of the STL such as Alexander Stepanov and Meng Lee. [4] [5] Although the C++ Standard Library and the STL share many features, neither is a strict superset of the other.
Several macros affect the definitions made by windows.h and the files it includes. UNICODE – when defined, this causes the generic text datatype TCHAR to be a synonym of WCHAR instead of CHAR, and all type-generic API functions and messages that work with text will be defined to the -W versions instead of the -A versions.
The second kind, defined as L"", produces a null-terminated array of type const wchar_t, where wchar_t is a wide-character of undefined size and semantics. Neither literal type offers support for string literals with UTF-8, UTF-16, or any other kind of Unicode encodings. C++11 supports three Unicode encodings: UTF-8, UTF-16, and UTF-32.