C++: string_view: Deep dive Jasmine Lopez Prithvi Okade 1Topics • Motivation • Performance benefits & basics • string_view: Constructors, useful functions • string vs. string_view and their interoperability interoperability • When to use string_view • Using string_view safely • Intro to span • span vs. string_view • Case study of an optimization using string_view. 2Motivation • Consider a function foo immutable string. • In C++ we generally will create it with following signature. 3 void foo(const std::string& str); string existing_str; foo(existing_str); foo("hello this is a long string"); This

example std::string text = "..."; text = SpellCheck(text); text = GrammarCheck(text);function composition is fundamental GrammarCheck(SpellCheck("..."))motivating example std::string SpellCheck(std::string SpellCheck(std::string text) { auto body = http::UrlEncode({"text", text}); auto response = http::Post("https://www.online-spellcheck.com", body); return response.body; }motivating example std::string SpellCheck(std::string SpellCheck(std::string text) { auto body = http::UrlEncode({"text", text}); auto response = http::Post("https://www.online-spellcheck.com", body); return response.body; }motivating example std::string SpellCheck(std::string

vector 容器初体验 & 迭代器入门 (BV1qF411T7sd) 2. 你所不知道的 set 容器 & 迭代器分类 (BV1m34y157wb) 3. string ， string_view ， const char * 的爱恨纠葛 ( 本期 ) 4. 万能的 map 容器全家桶及其妙用举例 5. 函子 functor 与 lambda 位的，标准规定只需满足 char <= short <= int <= long <= long long 即可）。 关于 char 类型的一个冷知识 C 语言中的字符串 • 字符串 (string) 就是由字符 (character) 组成的数组。 • C 语言中，字符串用双引号 “” 包裹，字符用单引号 ‘’ 包裹 。 • char c = ‘h’; • char s[] = “hello”; std::string 应运而生 封装的 std::string 应运而生 • string 可以从 const char * 隐式构造： • string s = “hello”; • string 具有 + 、 += 、 == 等直观的运算符重载： • string(“hello”) + string(“world”) == string(“helloworld”) • string 符合 vector

 String Formatting Improvements  Standard Library Modules  std::flat_(multi)map / std::flat_(multi)set  std::mdspan  std::generator  basic_string(_view)::contains()  Construct string(_view) string(_view) From nullptr  basic_string::resize_and_overwrite()  Monadic Operations for std::optional  Stacktrace Library  Changes to Ranges Library  Changes to Views Library  std::expected  std:  String Formatting Improvements  Standard Library Modules  std::flat_(multi)map / std::flat_(multi)set  std::mdspan  std::generator  basic_string(_view)::contains()  Construct string(_view)

Handling Phil Nash Error2018 2019series disappointments of a (total) Part 1int parse_int(std::string_view number)// TODO: +, -, digit separators? int acc = 0; for(char c : number) { *= 10; acc += c-'0'; } return acc; } int parse_int(std::string_view number) {int parse_int(std::string_view number) { int acc = 0; for(char c : number) { if(c < 42 0bool is_int(std::string_view number) { for(char c : number) { if(c < '0' || c > '9') return false; } return true; }bool is_int(std::string_view number) { for(char

async::then([] { return 42; }) | async::continue_on(s2) | async::then([] (int i) { return std::to_string(i); }) ; 1 2 3 4 5 6 7 8 auto r = comp | async::sync_wait(); 9 auto [str] = r.value_or(std::make_tuple(""_s)); async::then([] { return 42; }) | async::continue_on(s2) | async::then([] (int i) { return std::to_string(i); }) ; 1 2 3 4 5 6 7 8 auto r = comp | async::sync_wait(); 9 auto [str] = r.value_or(std::make_tuple(""_s)); async::then([] { return 42; }) 3 | async::continue_on(s2) 4 | async::then([] (int i) { return std::to_string(i); }) 5 6 ; 7 8 9 auto [str] = r.value_or(std::make_tuple(""_s)); 10 23.1Composition auto

of (string → string) C++ has this std::map class that does just what you want3 David Olsen — Back to Basics: Move Semantics — CppCon 2020 #include typedef std::mapstring, std::string> dictionary_t;4 typedef std::mapstring, std::string> dictionary_t;5 David Olsen — Back to Basics: Move Semantics — CppCon 2020 #include typedef std::mapstring, std::string> dictionary_t; dictionary_t Olsen — Back to Basics: Move Semantics — CppCon 2020 #include typedef std::mapstring, std::string> dictionary_t; dictionary_t build_dictionary( DbConnection db ) { dictionary_t dictionary;

References Recommendation 35class MyClass { std::string txt_; public: explicit MyClass(const std::string& txt): txt_(txt) {} explicit MyClass(std::string&& txt): txt_(std::move(txt)) {} }; CppCon MyClass { std::string txt1_; std::string txt2_; public: MyClass(const std::string& txt1, const std::string& txt2): txt1_(txt1), txt1_(txt1) {} MyClass(std::string&& txt1, std::string&& txt2): txt2_(std::move(txt2)) {} MyClass(const std::string& txt1, std::string&& txt2): txt1_(txt1), txt1_(std::move(txt1)) {} MyClass(std::string&& txt1, const std::string& txt2): txt1_(std::move(txt1)), txt2_(txt2)

convertStringToInt(std::string); int doubleInt(int); std::string convertIntToString(int);© 2018 Bloomberg Finance L.P. All rights reserved. Without functor 20 01: std::vectorstring> doubleNumbers(s doubleNumbers(std::vectorstring> input) 02: { 03: std::vectorstring> output; 04: for(auto str: input) 05: { 06: int asInt = convertStringToInt(str); 07: int doubled = doubleInt(asInt); reserved. vs. with functor 21 01: std::vectorstring> doubleNumbers(std::vectorstring> input) 02: { 03: std::vectorstring> output; 04: for(auto str: input) 05: { 06:

number | string | array | object Jonathan Müller — @foonathan Express your expectations CppCon 2023-10-03 8JSON grammar value = 'null' | 'true' | 'false' | number | string | array | object string = '"' expectations CppCon 2023-10-03 8JSON grammar value = 'null' | 'true' | 'false' | number | string | array | object string = '"' characters-or-escape '"' number = '-'? digits ('.' digits)? (('e'|'E') ('+'|'-') expectations CppCon 2023-10-03 8JSON grammar value = 'null' | 'true' | 'false' | number | string | array | object string = '"' characters-or-escape '"' number = '-'? digits ('.' digits)? (('e'|'E') ('+'|'-')