Character traits are an extremely important component of the streams and strings libraries because they allow the stream/string classes to separate out the logic of what characters are being stored from the logic of what manipulations should be performed on those characters. To begin with, the default character traits class, char_traits<T>, is used extensively in … Read more
There’s the free-function route, but unless you also provide overloads for std::string it’s a snake-pit. #include <string> #include <string_view> std::string_view sub_string( std::string_view s, std::size_t p, std::size_t n = std::string_view::npos) { return s.substr(p, n); } int main() { using namespace std::literals; auto source = “foobar”s; // this is fine and elegant… auto bar = sub_string(source, 3); … Read more
Since C++14 we have been able to create literal std::string #include <iostream> #include <string> int main() { using namespace std::string_literals; std::string s = “pl-\0-op”s; // <- Notice the “s” at the end // This is a std::string literal not // a C-String literal. std::cout << s << “\n”; } Before C++14 The problem is the … Read more
Get c-string out of std::string for conversion: NSString *errorMessage = [NSString stringWithCString:REALM.c_str() encoding:[NSString defaultCStringEncoding]];
Use boost::algorithm::join(..): #include <boost/algorithm/string/join.hpp> … std::string joinedString = boost::algorithm::join(elems, delim); See also this question.
It means not found. It is usually defined like so: static const size_t npos = -1; It is better to compare to npos instead of -1 because the code is more legible.
If you’re using a std::string, call length(): std::string str = “hello”; std::cout << str << “:” << str.length(); // Outputs “hello:5” If you’re using a c-string, call strlen(). const char *str = “hello”; std::cout << str << “:” << strlen(str); // Outputs “hello:5” Or, if you happen to like using Pascal-style strings (or f***** strings … Read more
It’s not allowed, because as per the standard 21.4.1 p6, invalidation of iterators/references is only allowed for — as an argument to any standard library function taking a reference to non-const basic_string as an argument. — Calling non-const member functions, except operator[], at, front, back, begin, rbegin, end, and rend. For a COW string, calling … Read more
EDIT Since c++17, some parts of the standard library were removed. Fortunately, starting with c++11, we have lambdas which are a superior solution. #include <algorithm> #include <cctype> #include <locale> // trim from start (in place) static inline void ltrim(std::string &s) { s.erase(s.begin(), std::find_if(s.begin(), s.end(), [](unsigned char ch) { return !std::isspace(ch); })); } // trim from … Read more
In C++11 you can use std::to_string: #include <string> std::string s = std::to_string(5); If you’re working with prior to C++11, you could use C++ streams: #include <sstream> int i = 5; std::string s; std::stringstream out; out << i; s = out.str(); Taken from http://notfaq.wordpress.com/2006/08/30/c-convert-int-to-string/