#include <string> #include <cassert> #include <utility> #include <type_traits> int main() { std::string mutableString = "Hello World!"; const std::string& constView = std::as_const(mutableString); assert( &constView == &mutableString ); assert( &std::as_const( mutableString ) =...
voidas_const(constT&&)=delete; (2)(C++17 起) 1)将左值引用组成t的 const 类型 2)删除 const 右值引用重载,以禁止右值参数 可能的实现 template<classT>constexprstd::add_const_t<T>&as_const(T&t)noexcept{returnt;} 示例 运行此代码 #include <string>#include <cassert>#include <utility>#includ...
#include <cassert> #include <string> #include <type_traits> #include <utility> int main() { std::string mutableString = "Hello World!"; auto&& constRef = std::as_const(mutableString); mutableString.clear(); // OK // constRef.clear(); // Error: 'constRef' is 'const' qualified...
size_tsize()const{size_tret = ml_.size_;if/* constexpr */(kIsLittleEndian) {// We can save a couple instructions, because the category is// small iff the last char, as unsigned, is <= maxSmallSize.typedeftypenamestd::make_unsigned<Char>::type UChar;automaybeSmallSize =size_t(maxSm...
void operator()(int i) const { std::cout << i << '\n'; } }; int main(){ // 调用自由函数 std::invoke(print_num, -9); // 调用 lambda std::invoke([]() { print_num(42); }); // 调用成员函数 const Foo foo(314159); ...
#include<optional>// 函数返回类型由string改成了optional<string>std::optional<string>ReadFileAsString(conststring& path){ifstreamstream(path); string res;if(stream) { ...//做读取操作, 存到res中stream.close();returnres;//}elsereturn{};//注意返回的是空的}intmain(){ ...
"c1.c", line 15: Error: Cannot assign const std::complex<double> to std::complex<X> without "std::complex<X>::operator=(const std::complex<X>&)";. "c1.c", line 16: Error: The operation "std::complex<X> += const std::complex<double>" is illegal. ...
char buf[256]; if (NULL == (pipe = _popen(pCmd.c_str(), "rt"))) { return; } while (!feof(pipe)) { if (fgets(buf, 256, pipe) != NULL) { f.push_back(string(buf)); } } _pclose(pipe); } void WriteFiles (const char* file_name) ...
using namespace std; int reading(const char *d_path) { cout<<"In Reading"<<endl; /*bfs::path pathSource("c:\\Program Files\\");*/ struct stat info; // DIR *dir; struct dirent *ent; dir= opendir (d_path); cout<<dir<<endl; if ((dir = opendir (d_path)) != NULL) { ...
#include <cstdio>#include <filesystem>#include <print>intmain(){std::print("{2} {1}{0}!\n",23,"C++","Hello");// overload (1)constautotmp{std::filesystem::temp_directory_path()/"test.txt"};if(std::FILE*stream{std::fopen(tmp.c_str(),"w")}){std::print(stream,"File: ...