Linux Manuals

std::optional<T>::operator->,std::optional<T>::operator* – std::optional<T>::operator->,std::optional<T>::operator* Synopsis constexpr const T* operator->() const; (1) (since C++17) constexpr T* operator->(); (1) (since C++17) constexpr const T& operator*() const&; (2) (since C++17) constexpr T& operator*() &; (2) (since C++17) constexpr const T&& operator*() const&&; (2) (since C++17) constexpr T&& operator*() &&; (2) (since C++17) Accesses the contained value. 1) Returns a…

std::optional<T>::emplace – std::optional<T>::emplace Synopsis template< class… Args > (since C++17) T& emplace( Args&&… args ); template< class U, class… Args > (since C++17) T& emplace( std::initializer_list<U> ilist, Args&&… args ); Constructs the contained value in-place. If *this already contains a value before the call, the contained value is destroyed by calling its destructor. 1) Initializes…

std::optional – std::optional Synopsis Defined in header <optional> template< class T > (since C++17) class optional; The class template std::optional manages an optional contained value, i.e. a value that may or may not be present. A common use case for optional is the return value of a function that may fail. As opposed to other…

std::operator==,!=,<(std::error_code) – std::operator==,!=,<(std::error_code) Synopsis Defined in header <system_error> bool operator==( const error_code& lhs, const error_code& rhs ) noexcept; (1) (since C++11) bool operator!=( const error_code& lhs, const error_code& rhs ) noexcept; (1) (since C++11) bool operator<( const error_code& lhs, const error_code& rhs ) noexcept; (1) (since C++11) Compares two error code objects. 1) Compares lhs…

std::operator+(std::basic_string) – std::operator+(std::basic_string) Synopsis template <class CharT, class Traits, class Alloc> basic_string<CharT, Traits, Alloc>(1) operator+(const basic_string<CharT, Traits, Alloc> &lhs, const basic_string<CharT, Traits, Alloc> &rhs); template <class CharT, class Traits, class Alloc> basic_string<CharT, Traits, Alloc>(2) operator+(const basic_string<CharT, Traits, Alloc> &lhs, const CharT *rhs); template <class CharT, class Traits, class Alloc> basic_string<CharT, Traits, Alloc>(3) operator+(const basic_string<CharT, Traits,…

std::once_flag – std::once_flag Synopsis Defined in header <mutex> class once_flag; (since C++11) The class std::once_flag is a helper structure for std::call_once. An object of type std::once_flag that is passed to multiple calls to std::call_once allows those calls to coordinate with each other such that only one of the calls will actually run to completion. std::once_flag…

std::basic_ofstream – std::basic_ofstream Synopsis Defined in header <fstream> template< class CharT, class Traits = std::char_traits<CharT> > class basic_ofstream : public std::basic_ostream<CharT, Traits> The class template basic_ofstream implements high-level output operations on file based streams. It interfaces a file-based streambuffer (std::basic_filebuf) with the high-level interface of (std::basic_ostream). A typical implementation of std::basic_ofstream holds only one non-derived…

std::numpunct_byname – std::numpunct_byname Synopsis Defined in header <locale> template< class CharT > class numpunct_byname : public std::numpunct<CharT>; std::numpunct_byname is a std::numpunct facet which encapsulates numeric punctuation preferences of a locale specified at its construction. Two specializations are provided by the standard library Defined in header <locale> std::numpunct_byname<char> locale-specific std::numpunct facet for narrow character I/O std::numpunct_byname<wchar_t>…

std::numpunct<CharT>::truename,do_truename,falsename,do_falsename – std::numpunct<CharT>::truename,do_truename,falsename,do_falsename Synopsis Defined in header<locale> public : (1) string_type truename() const; public: (2) string_type falsename() const; protected: (3) virtual string_type do_truename() const; protected: (4) virtual string_type do_falsename() const; 1-2) Public member function, calls the member function do_truename and do_falsename of the most derived class respectively. 3) Returns the string to be used as…

std::numpunct<CharT>::thousands_sep,do_thousands_sep – std::numpunct<CharT>::thousands_sep,do_thousands_sep Synopsis Defined in header<locale> public : (1) char_type thousands_sep() const; protected: (2) virtual char_type do_thousands_sep() const; 1) Public member function, calls the member function do_thousands_sep of the most derived class. 2) Returns the character to be used as the separator between digit groups when parsing or formatting integers and integral parts of…

std::numpunct<CharT>::~numpunct – std::numpunct<CharT>::~numpunct Synopsis Defined in header <locale> protected: ~numpunct(); Destructs a std::numpunct facet. This destructor is protected and virtual (due to base_class destructor being virtual). An object of type std::numpunct, like most facets, can only be destroyed when the last std::locale object that implements this facet goes out of scope or if a user-defined…

std::numpunct<CharT>::grouping,std::numpunct<CharT>::do_grouping – std::numpunct<CharT>::grouping,std::numpunct<CharT>::do_grouping Synopsis Defined in header<locale> public : (1) std::string grouping() const; protected: (2) virtual std::string do_grouping() const; 1) Public member function, calls the member function do_grouping of the most derived class. 2) Returns an std::string holding, in each char element, the number of digits in each group of the numeric output formatted by…

std::numpunct<CharT>::decimal_point,do_decimal_point – std::numpunct<CharT>::decimal_point,do_decimal_point Synopsis Defined in header<locale> public : (1) char_type decimal_point() const; protected: (2) virtual char_type do_decimal_point() const; 1) Public member function, calls the member function do_decimal_point of the most derived class. 2) Returns the character to be used as the decimal separator between integer and fractional parts. Return value The value of type…

std::numpunct – std::numpunct Synopsis Defined in header <locale> template< class CharT > class numpunct; The facet std::numpunct encapsulates numeric punctuation preferences. Stream I/O operations use std::numpunct through std::num_get and std::num_put for parsing numeric input and formatting numeric output. The numbers that are supported by std::numpunct have the format described below. Here digit represents the radix…

std::numeric_limits<T>::traps – std::numeric_limits<T>::traps Synopsis static const bool traps; (until C++ 11) static constexpr bool traps; (since C++ 11) The value of std::numeric_limits<T>::traps is true for all arithmetic types T that have at least one value that, if used as an argument to an arithmetic operation, will generate a trap. Standard specializations T value of std::numeric_limits<T>::traps…

std::numeric_limits<T>::tinyness_before – std::numeric_limits<T>::tinyness_before Synopsis static const bool tinyness_before; (until C++ 11) static constexpr bool tinyness_before; (since C++ 11) The value of std::numeric_limits<T>::tinyness_before is true for all floating-point types T that test results of floating-point expressions for underflow before rounding. Standard specializations T value of std::numeric_limits<T>::tinyness_before /* non-specialized */ false bool false char false signed char…

std::numeric_limits<T>::signaling_NaN – std::numeric_limits<T>::signaling_NaN Synopsis static T signaling_NaN() throw(); (until C++11) static constexpr T signaling_NaN() noexcept; (since C++11) Returns the special value "signaling not-a-number", as represented by the floating-point type T. Only meaningful if std::numeric_limits<T>::has_signaling_NaN == true. In IEEE 754, the most common binary representation of floating-point numbers, any value with all bits of the exponent…

std::numeric_limits<T>::round_style – std::numeric_limits<T>::round_style Synopsis static const std::float_round_style round_style; (until C++ 11) static constexpr std::float_round_style round_style; (since C++ 11) The value of std::numeric_limits<T>::round_style identifies the rounding style used by the floating-point type T whenever a value that is not one of the exactly repesentable values of T is stored in an object of that type. Standard…

std::numeric_limits<T>::round_error – std::numeric_limits<T>::round_error Synopsis static T round_error() throw(); (until C++11) static constexpr T round_error() noexcept; (since C++11) Returns the largest possible rounding error in ULPs (units in the last place) as defined by ISO 10967, which can vary from 0.5 (rounding to the nearest digit) to 1.0 (rounding to zero or to infinity). It is…

std::numeric_limits<T>::radix – std::numeric_limits<T>::radix Synopsis static const int radix; (until C++ 11) static constexpr int radix; (since C++ 11) The value of std::numeric_limits<T>::radix is the base of the number system used in the representation of the type. It is 2 for all binary numeric types, but it may be, for example, 10 for IEEE 754 decimal_floating-point_types…