deduction guides for std::basic_string_view

 

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basic_string

basic_string_view (C++17)

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std::basic_string_view

Member functions basic_string_view::basic_string_view    basic_string_view::operator= Iterators basic_string_view::beginbasic_string_view::cbegin basic_string_view::endbasic_string_view::cend basic_string_view::rbeginbasic_string_view::crbegin basic_string_view::rendbasic_string_view::crend Element access basic_string_view::at basic_string_view::operator[] basic_string_view::front basic_string_view::back basic_string_view::data Capacity basic_string_view::sizebasic_string_view::length basic_string_view::max_size basic_string_view::empty Modifiers basic_string_view::remove_prefix basic_string_view::remove_suffix basic_string_view::swap

Operations basic_string_view::copy basic_string_view::substr basic_string_view::compare basic_string_view::starts_with (C++20) basic_string_view::ends_with (C++20) basic_string_view::contains (C++23) basic_string_view::find basic_string_view::rfind basic_string_view::find_first_of basic_string_view::find_last_of basic_string_view::find_first_not_of basic_string_view::find_last_not_of Constants basic_string_view::npos Non-member functions operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) operator<< operator""sv Helper classes hash<std::string_view>hash<std::wstring_view>hash<std::u8string_view>hash<std::u16string_view>hash<std::u32string_view> (C++20) Deduction guides(C++20)

 

Defined in header <string_view>
template< class It, class End > basic_string_view( It, End ) -> basic_string_view<std::iter_value_t<It>>;	(1)	(since C++20)
template< class R > basic_string_view( R&& ) -> basic_string_view<ranges::range_value_t<R>>;	(2)	(since C++23)

These deduction guides are provided for std::basic_string_view.

1) This deduction guide allow the character type to be deduced from the iterator-sentinel pair. This overload participates in overload resolution only if It satisfies contiguous_iterator and End satisfies sized_sentinel_for for It.

2) This deduction guide allow the character type to be deduced from the range. This overload participates in overload resolution only if R satisfies contiguous_range.

Example

Run this code

#include <array>
#include <iostream>
#include <string_view>
 
int main()
{
    std::array a1{'n', 'u', 'c', 'l', 'e', 'o', 'n', 's', ':', '\n'};
    std::basic_string_view s1(a1.cbegin(), a1.cend()); // deduction: CharT -> char
    static_assert(std::is_same_v<decltype(s1)::value_type, char>);
    std::cout << s1;
 
    std::array a2{L'p', L'r', L'o', L't', L'o', L'n', L's', L'\n'};
    std::basic_string_view s2(a2.cbegin(), a2.cend()); // deduction: CharT -> wchar_t
    static_assert(std::is_same_v<decltype(s2)::value_type, wchar_t>);
    std::wcout << s2;
 
    std::array<long, 9> a3{'n', 'e', 'u', 't', 'r', 'o', 'n', 's', '\n'};
    std::basic_string_view s3(a3.cbegin(), a3.cend()); // deduction: CharT -> long
    static_assert(std::is_same_v<decltype(s3)::value_type, long>);
    for (const auto e : s3)
        std::cout << static_cast<char>(e);
}

Output:

nucleons:
protons
neutrons