template<class T>struct Alloc{}; template<class T>using Vec= vector<T, Alloc<T>>;// type-id is vector<T, Alloc<T>> Vec<int> v;// Vec<int> is the same as vector<int, Alloc<int>>

template<typename...>using void_t=void; template<typename T>void_t<typename T::foo> f(); f<int>();// error, int does not have a nested type foo

template<class T>struct A; template<class T>using B=typename A<T>::U;// type-id is A<T>::U template<class T>struct A{typedef B<T> U;}; B<short> b;// error: B<short> uses its own type via A<short>::U

#include <iostream>#include <string>#include <type_traits>#include <typeinfo> // type alias, identical to// typedef std::ios_base::fmtflags flags;using flags=std::ios_base::fmtflags;// the name 'flags' now denotes a type:flags fl=std::ios_base::dec; // type alias, identical to// typedef void (*func)(int, int);using func=void(*)(int,int); // the name 'func' now denotes a pointer to function:void example(int,int){}func f= example; // alias templatetemplate<class T>using ptr= T*;// the name 'ptr<T>' is now an alias for pointer to Tptr<int> x; // type alias used to hide a template parametertemplate<class CharT>using mystring=std::basic_string<CharT,std::char_traits<CharT>>; mystring<char> str; // type alias can introduce a member typedef nametemplate<typename T>struct Container{using value_type= T;}; // which can be used in generic programmingtemplate<typename ContainerT>void info(const ContainerT& c){typename ContainerT::value_type T;std::cout<<"ContainerT is `"<<typeid(decltype(c)).name()<<"`\n""value_type is `"<<typeid(T).name()<<"`\n";} // type alias used to simplify the syntax of std::enable_iftemplate<typename T>using Invoke=typename T::type; template<typename Condition>using EnableIf= Invoke<std::enable_if<Condition::value>>; template<typename T,typename= EnableIf<std::is_polymorphic<T>>>int fpoly_only(T){return1;} struct S{virtual ~S(){}}; int main(){    Container<int> c;    info(c);// Container::value_type will be int in this function//  fpoly_only(c); // error: enable_if prohibits this    S s;    fpoly_only(s);// okay: enable_if allows this}

ContainerT is `struct Container<int>`value_type is `int`