Linux Manuals

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)

std::valarray<T>::sum – std::valarray<T>::sum Synopsis T sum() const; Computes the sum of the elements. The function can be used only if operator+= is defined for type T. If the std::valarray is empty, the behavior is undefined. The order in which the elements are processed by this function is unspecified. Parameters (none) Return value The sum of…

std::valarray<T>::size – std::valarray<T>::size Synopsis std::size_t size() const; Returns the number of elements in the valarray. Parameters (none) Return value Number of elements in the valarray. Example // Run this code #include <iostream> #include <valarray> int main() { std::valarray<double> a = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; std::cout << "Average: " <<…

std::valarray<T>::shift – std::valarray<T>::shift Synopsis valarray<T> shift(int count) const; Returns a new valarray of the same size with elements whose positions are shifted by count elements. The new position of each element is i−count where i is the previous position. The value of shifted in elements is T(). Parameters count – number of positions to shift…

std::valarray<T>::resize – std::valarray<T>::resize Synopsis void resize(std::size_t count, T value = T()); Resizes the valarray to contain count elements and assigns value to each element. This functions invalidates all pointers and references to elements in the array. Parameters count – new size of the container value – the value to initialize the new elements with Return…

std::valarray<T>::operator[] – std::valarray<T>::operator[] Synopsis T operator[]( std::size_t pos ) const; (until C++11) const T& operator[]( std::size_t pos ) const; (since C++11) T& operator[]( std::size_t pos ); (2) std::valarray<T> operator[]( std::slice slicearr ) const; (3) std::slice_array<T> operator[]( std::slice slicearr ); (4) std::valarray<T> operator[]( const std::gslice& gslicearr ) const; (1) (5) std::gslice_array<T> operator[]( const std::gslice& gslicearr );…

std::valarray<T>::min – std::valarray<T>::min Synopsis T min() const; Computes the minimum value of the elements. If there are no elements, the behavior is undefined. The function can be used only if operator< is defined for type T. Parameters (none) Return value The minimum of the elements. Example // Run this code #include <valarray> #include <iostream> int…

std::valarray<T>::max – std::valarray<T>::max Synopsis T max() const; Computes the maximum value of the elements. If there are no elements, the behavior is undefined. The function can be used only if operator< is defined for type T. Parameters (none) Return value The maximum of the elements. Example // Run this code #include <valarray> #include <iostream> int…

std::valarray<T>::cshift – std::valarray<T>::cshift Synopsis valarray<T> cshift(int count) const; Returns a new valarray of the same size with elements whose positions are shifted circularly by count elements. The new position of each element is (i−count) mod s where i is the previous position and s is size(). Parameters count – number of positions to shift the…

std::valarray<T>::apply – std::valarray<T>::apply Synopsis valarray<T> apply(T func(T)) const; valarray<T> apply(T func(const T &)) const; Returns a new valarray of the same size with values which are acquired by applying function func to the previous values of the elements. Parameters func – function to apply to the values Return value The resulting valarray with values acquired…

std::valarray – std::valarray Synopsis Defined in header <valarray> template< class T > class valarray; std::valarray is the class for representing and manipulating arrays of values. It supports element-wise mathematical operations and various forms of generalized subscript operators, slicing and indirect access. Notes std::valarray and helper classes are defined to be free of certain forms of…

std::va_list – std::va_list Synopsis Defined in header <cstdarg> typedef /* unspecified */ va_list; va_list is a complete object type suitable for holding the information needed by the macros va_start, va_copy, va_arg, and va_end. If a va_list instance is created, passed to another function, and used via va_arg in that function, then any subsequent use in…

std::uses_allocator_construction_args – std::uses_allocator_construction_args Synopsis Defined in header<memory> T is not a specialization of std::pair template <class T, class Alloc, class… Args> std::tuple</*see below*/> uses_allocator_construction_args((1)(since C++ 20) const Alloc &alloc, Args &&…args); T is a specialization of std::pair template <class T, class Alloc, class Tuple1, class Tuple2> std::tuple</*see below*/> uses_allocator_construction_args((2)(since C++ 20) const Alloc &alloc, std::piecewise_construct_t,…

std::uses_allocator<std::tuple> – std::uses_allocator<std::tuple> Synopsis Defined in header<tuple> template <class… Types, class Alloc> (since C++ 11) struct uses_allocator<std::tuple<Types…>, Alloc> : std::true_type { }; This specialization of std::uses_allocator informs other library components that tuples support uses-allocator construction, even though they do not have a nested allocator_type. Inherited from std::integral_constant Member constants value true          (public static member constant)…

std::use_facet – std::use_facet Synopsis Defined in header<locale> template <class Facet> const Facet &use_facet(const std::locale &loc); Obtains a reference to a facet implemented by loc. Parameters loc – the locale object to query Return value Returns a reference to the facet. The reference returned by this function is valid as long as any std::locale object exists…

std::uppercase,std::nouppercase – std::uppercase,std::nouppercase Synopsis Defined in header <ios> std::ios_base& uppercase( std::ios_base& str ); (1) std::ios_base& nouppercase( std::ios_base& str ); (2) Enables the use of uppercase characters in floating-point and hexadecimal integer output. Has no effect on input. 1) enables the uppercase flag in the stream str as if by calling str.setf(std::ios_base::uppercase) 2) disables the uppercase…