VC编译器对FunctionTemplate实例化的优化：
看下面Template代码：
inline int const& max (int const& a, int const& b)
{
return a<b?b:a;
}
// maximum of two values of any type
template <typename T>
inline T const& max (T const& a, T const& b)
{
return a<b?b:a;
}
// maximum of three values of any type
template <typename T>
inline T const& max (T const& a, T const& b, T const& c)
{
return max (max(a,b), c);
}
inline int const& max (int const& a, int const& b) 已经是template <typename T>
inline T const& max (T const& a, T const& b) 对类型int的实例化，所以，凡是需要调用max<int>时，VC 编译器都不在再用max<int>来Instantiate max Function Template.
int main ()
{
::max(7, 42, 68); // calls the template for three arguments first, then call inline int const& max
::max(7.0, 42.0); // calls max<double> (by argument deduction)
::max('a', 'b'); // calls max<char> (by argument deduction)
::max(7, 42); // calls the nontemplate for two ints
::max<>(7, 42); // call inline int const& max
::max<int>(7, 42); // call inline int const& max
::max<int>(7.0, 42.0); // call inline int const& max
::max<double>(7, 42); // calls max<double> (no argument deduction)
return 0;
}