Section 3: library functions
std::vwscanf,std::vfwscanf,std::vswscanf – std::vwscanf,std::vfwscanf,std::vswscanf Synopsis Defined in header <cwchar> int vwscanf( const wchar_t* format, va_list vlist ); (1) (since C++11) int vfwscanf( std::FILE* stream, const wchar_t* format, va_list vlist ); (2) (since C++11) int vswscanf( const wchar_t* buffer, const wchar_t* format, va_list vlist ); (3) (since C++11) Reads data from the a variety of sources, interprets…
std::vwprintf,std::vfwprintf,std::vswprintf – std::vwprintf,std::vfwprintf,std::vswprintf Synopsis Defined in header<cwchar> int vwprintf(const wchar_t *format, va_list vlist); (1) int vfwprintf(std::FILE *stream, const wchar_t *format, va_list vlist); (2) int vswprintf(const wchar_t *buffer, std::size_t buf_size, (3) const wchar_t *format, va_list vlist); Loads the data from locations, defined by vlist,, converts them to wide string equivalents and writes the results to a…
std::vscanf,std::vfscanf,std::vsscanf – std::vscanf,std::vfscanf,std::vsscanf Synopsis Defined in header <cstdio> int vscanf( const char* format, va_list vlist ); (1) (since C++11) int vfscanf( std::FILE* stream, const char* format, va_list vlist ); (2) (since C++11) int vsscanf( const char* buffer, const char* format, va_list vlist ); (3) (since C++11) Reads data from the a variety of sources, interprets…
std::vprintf,std::vfprintf,std::vsprintf,std::vsnprintf – std::vprintf,std::vfprintf,std::vsprintf,std::vsnprintf Synopsis Defined in header <cstdio> int vprintf( const char* format, va_list vlist ); (1) int vfprintf( std::FILE* stream, const char* format, va_list vlist ); (2) int vsprintf( char* buffer, const char* format, va_list vlist ); (3) int vsnprintf( char* buffer, std::size_t buf_size, const char* format, va_list vlist ); (4) (since C++11) Loads…
std::void_t – std::void_t Synopsis Defined in header<type_traits> template <class…> (since C++ 17) using void_t = void; Utility metafunction that maps a sequence of any types to the type void Notes This metafunction is used in template metaprogramming to detect ill-formed types in SFINAE context: template <typename… Ts> struct make_void { typedef void type; }; template…
std::visit – std::visit Synopsis Defined in header <variant> template <class Visitor, class… Variants> (1) (since C++17) constexpr /*see below*/ visit(Visitor&& vis, Variants&&… vars); template <class R, class Visitor, class… Variants> (2) (since C++20) constexpr R visit(Visitor&&, Variants&&…); Applies the visitor vis to the variants vars Effectively returns std::invoke(std::forward<Visitor>(vis), std::get<is>(std::forward<Variants>(vars))…) , where is… is vars.index()…. 1)…
std::vector<bool>::reference – std::vector<bool>::reference Synopsis class reference; The std::vector<bool> specialization defines std::vector<bool>::reference as a publicly-accessible nested class. std::vector<bool>::reference proxies the behavior of references to a single bit in std::vector<bool>. The primary use of std::vector<bool>::reference is to provide an l-value that can be returned from operator[]. Any reads or writes to a vector that happen via a…
std::vector<bool> – std::vector<bool> Synopsis Defined in header <vector> template<class Allocator> class vector<bool, Allocator>; std::vector<bool> is a possibly space-efficient specialization of std::vector for the type bool. The manner in which std::vector<bool> is made space efficient (as well as whether it is optimized at all) is implementation defined. One potential optimization involves coalescing vector elements such that…
std::variant_size,std::variant_size_v – std::variant_size,std::variant_size_v Synopsis Defined in header<variant> template <class T> (1)(since C++ 17) struct variant_size; /* undefined */ template <class… Types> struct variant_size<std::variant<Types…>>(2)(since C++ 17) : std::integral_constant<std::size_t, sizeof…(Types)> { }; template <class T> class variant_size<const T>; template <class T> class variant_size<volatile T>; (3)(since C++ 17) template <class T> class variant_size<const volatile T>; Provides access to…
std::variant_npos – std::variant_npos Synopsis Defined in header <variant> inline constexpr std::size_t variant_npos = -1; (since C++17) This is a special value equal to the largest value representable by the type std::size_t, used as the return type of index() when valueless_by_exception() is true See also returns the zero-based index of the alternative held by the variant…
std::variant_alternative,std::variant_alternative_t – std::variant_alternative,std::variant_alternative_t Synopsis Defined in header<variant> template <std::size_t I, class T> (1)(since C++ 17) struct variant_alternative; /* undefined */ template <size_t I, class… Types> (2)(since C++ 17) struct variant_alternative<I, variant<Types…>>; template <size_t I, class T> class variant_alternative<I, const T>; template <size_t I, class T> class variant_alternative<I, volatile T>; (3)(since C++ 17) template <size_t I,…
std::variant<Types…>::~variant – std::variant<Types…>::~variant Synopsis ~variant(); (since C++17) If valueless_by_exception is true, does nothing. Otherwise, destroys the currently contained value. This destructor is trivial if std::is_trivially_destructible_v<T_i> is true for all T_i in Types…
std::variant<Types…>::valueless_by_exception – std::variant<Types…>::valueless_by_exception Synopsis constexpr bool valueless_by_exception() const noexcept; (since C++17) Returns false if and only if the variant holds a value. Notes A variant may become valueless in the following situations: * (guaranteed) an exception is thrown during the move initialization of the contained value from the temporary in copy_assignment * (guaranteed) an exception…
std::variant<Types…>::swap – std::variant<Types…>::swap Synopsis void swap(variant &rhs) noexcept(/* see below */); (1)(since C++ 17) Swaps two variant objects. * if both *this and rhs are valueless by exception, does nothing * otherwise, if both *this and rhs hold the same alternative, calls swap(std::get<i>(*this), std:get<i>(rhs)) where i is index(). If an exception is thrown, the state…
std::variant<Types…>::operator= – std::variant<Types…>::operator= Synopsis constexpr variant &operator=(const variant &rhs); (1)(since C++ 17) constexpr variant & operator=(variant &&rhs) noexcept(/* see below */); (2)(since C++ 17) template <class T> variant &operator=(T &&t) noexcept(/* see below */); (3)(since C++ 17) Assigns a new value to an existing variant object. 1) Copy-assignment: * If both *this and rhs are…
std::variant<Types…>::index – std::variant<Types…>::index Synopsis constexpr std::size_t index() const noexcept; (since C++17) Returns the zero-based index of the alternative that is currently held by the variant. If the variant is valueless_by_exception, returns variant_npos. Example // Run this code #include <variant> #include <string> #include <iostream> int main() { std::variant<int, std::string> v = "abc"; std::cout << "v.index =…
std::variant<Types…>::emplace – std::variant<Types…>::emplace Synopsis template <class T, class… Args> (1) (since C++17) T& emplace(Args&&… args); template <class T, class U, class… Args> (2) (since C++17) T& emplace(std::initializer_list<U> il, Args&&… args); template <size_t I, class… Args> (3) (since C++17) std::variant_alternative_t<I, variant>& emplace(Args&&… args); template <size_t I, class U, class… Args> (4) (since C++17) std::variant_alternative_t<I, variant>& emplace(std::initializer_list<U>…
std::variant – std::variant Synopsis Defined in header <variant> template <class… Types> (since C++17) class variant; The class template std::variant represents a type-safe union. An instance of std::variant at any given time either holds a value of one of its alternative types, or in the case of error – no value (this state is hard to…
std::valarray<T>::~valarray – std::valarray<T>::~valarray Synopsis ~valarray() Destructs the numeric array. The destructors of the elements are called and the used storage is deallocated. Complexity Linear in the size of the numeric array.
std::valarray<T>::swap – std::valarray<T>::swap Synopsis void swap(valarray &other); (until C++ 11) void swap(valarray &other) noexcept; (since C++ 11) Swaps the contents with those of other. Parameters other – another valarray to swap the contents with Return value (none)