Literal suffixes for basic_string_view

Introduction

When we adopted basic_string_view into the standard library from the Library Fundamentals TS, we did not define any literal suffixes for the type.

We adopted the ""s suffix for basic_string to make it easy to declare string variables. We should do the same for basic_string_view. This would make declaring a string_view from a constant string simple:

std::string_view sv = "ABCD"sv;

These operators should be constexpr, since the constructors for string_view are constexpr.

Bikeshedding

In this paper, I am assuming that we will use the literal suffix ""sv for this feature. Of course, this is subject to bikeshedding.

Wording

This is relative to N4606:

Add to the end of section [string.view.synop] (after "hash support")

inline namespace literals { inline namespace string_view_literals {

// 21.4.X, _suffix for basic_string_view literals:_

constexpr string_view    operator "" sv(const char* str, size_t len) noexcept;
constexpr u16string_view operator "" sv(const char16_t* str, size_t len) noexcept;
constexpr u32string_view operator "" sv(const char32_t* str, size_t len) noexcept;
constexpr wstring_view   operator "" sv(const wchar_t* str, size_t len) noexcept;
}}

Add a new section after [string.view.hash]:

[ Note to the editor: The structure here is identical to [basic.string.literals] ]

21.4.X Suffix for basic_string_view literals [basic.string_view.literals]

constexpr string_view operator "" sv(const char* str, size_t len) noexcept;

1. Returns: string_view{str, len}.

constexpr u16string_view operator "" sv(const char16_t* str, size_t len) noexcept;

1. Returns: u16string_view{str, len}.

constexpr u32string_view operator "" sv(const char32_t* str, size_t len) noexcept;

1. Returns: u32string_view{str, len}.

constexpr wstring_view operator "" sv(const wchar_t* str, size_t len) noexcept;

1. Returns: wstring_view{str, len}.