Sometimes we want to preserve the string format especially when we use string in a string with /”. In C++14 and above, there is a std::quoted template that allows handling strings safely where they may contain spaces and special characters and it keeps their formatting intact. In this post, we explain std::quoted quoted strings in modern C++.
What Is Quoted String In Modern C++?
The std::quoted template is included in <iomanip> header, and it is used to handle strings (i.e. “Let’s learn from \”LearnCPlusPlus.org!\” “) safely where they may contain spaces and special characters and it keeps their formatting intact.
Here is the syntax,
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std::quoted( <basic_string> ) |
Here are C++14 templates defined in <iomanip> where the string is used as input,
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template< class CharT > quoted( const CharT* s, CharT delim = CharT('"'), CharT escape = CharT('\\') ); |
or
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template< class CharT, class Traits, class Allocator > quoted( const std::basic_string<CharT, Traits, Allocator>& s, CharT delim = CharT('"'), CharT escape = CharT('\\') ); |
Here is a C++14 template defined in <iomanip> where the string is used as output,
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template< class CharT, class Traits, class Allocator > quoted( std::basic_string< CharT, Traits, Allocator>& s, CharT delim=CharT('"'), CharT escape=CharT('\\') ); |
Note that this feature is is using std::basic_string and it improved in C++17 by the std::basic_string_view support.
What Is std::quoted quoted string in modern C++?
Here is an example that uses input string and outputs into a stringstream:
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const std::string str = "I say \"LearnCPlusPlus!\""; std::stringstream sstr; sstr << std::quoted(str); // input str to sstr |
Here is an example that uses stringstream as an input and outputs into a string.
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std::string str_out; sstr >> std::quoted(str_out); // output sstr to str_out |
Is there a full example about std::quoted quoted string in modern C++?
Here is a full example about std::quoted in modern C++.
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#include <iostream> #include <sstream> #include <iomanip> int main() { std::stringstream sstr; const std::string str = "Let's learn from \"LearnCPlusPlus.org!\" "; sstr << std::quoted(str); // input str to sstr std::cout << str << std::endl; std::cout << sstr.str() << std::endl; std::string str_out; sstr >> std::quoted(str_out); // output sstr to str_out std::cout << str_out << std::endl; system("pause"); return 0; } int main() { constexpr char c = checksize(8); std::cout << c << std::endl; system("pause"); return 0; } |
For more information about this feature, please see https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3654.html
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