When usingstd::any, it underlines it in red with the messagenamespace "std" has no member "any", but the code compiles and runs fine Steps to reproduce Create a new C++ file Paste in the following content: #include<any>intmain() { std::any xyz =4;return0; } std::anyshould be ...
命名空间把对象,函数,变量等分组,然后有一个名字。 The format of namespaces is: namespace identifier { entities } Whereidentifieris any valid identifier andentitiesis the set of classes, objects and functions that are included within the namespace.For example: 实体可以是任何有效的标识符。 namespace...
匿名命名空间,就是没有名字的namespace,如下所示: #include<iostream>namespace// unnamed namespace{voiddoSomething()// can only be accessed in this file{ std::cout <<"v1\n"; } }intmain(){doSomething();// we can call doSomething() without a namespace prefixreturn0; } 匿名命名空间的作...
usingnamespacestd的作用我觉得在介绍usingnamespacestd的作用之前,应该先讲一下如果没有usingnamespacestd这句代码,会对你的代码以及编程效率会有什么影响。删掉usingnamespacestd的影响最直观的一个影响就是,你的cin和cout就不能用的那么简洁明了了。 正常情况下,例如我要输出一个hello world! C++代码是:# ...
有如下程序: #includeiostream usingnamespacestd; classtestclass {public: virtualvoidfunl() {coutfunltestclass;} virtualvoidfun2() {coutfun2testclass;}}; classtestclassl:publictestclass {voidfun() {coutfunltestclassl;}}; intmain() {testclassobj1,*p; testclasslobj2; p=&obj2; p-fun1...
template<typename _Iterator> auto when_any( _Iterator _Begin, _Iterator _End, const task_options& _TaskOptions = task_options()) -> decltype ( details::_WhenAnyImpl< typename std::iterator_traits<_Iterator>::value_type::result_type, _Iterator>::_Perform(_TaskOptions, _Begin, _End));...
template<typename _Iterator> auto when_any( _Iterator _Begin, _Iterator _End, const task_options& _TaskOptions = task_options()) -> decltype ( details::_WhenAnyImpl< typename std::iterator_traits<_Iterator>::value_type::result_type, _Iterator>::_Perform(_TaskOptions, _Begin, _End)); ...
1template <typename std::stringobj>2voidfunc1()3{4//...5}67template <typenamedoubled>8voidfunc2()9{10//...11} 以上两个例子都是错误的。第一个用了类类型std::string的对象作为template parameter,而第二个用double类型的变量作为template parameter。