模板是什么意思?在 C++ 中使用空尖括号?
template<>
class A{
//some class data
};
这种代码我见过很多次了.上面代码中template<>的作用是什么?在哪些情况下我们需要强制使用它?
I have seen this kind of code many times.
what is the use of template<> in the above code?
And what are the cases where we need mandate the use of it?
推荐答案
template<> 告诉编译器遵循模板特化，特别是完全特化.通常，class A 应该是这样的:
template<> tells the compiler that a template specialization follows, specifically a full specialization. Normally, class A would have to look something like this:
template<class T>
class A{
// general implementation
};
template<>
class A<int>{
// special implementation for ints
};
现在，每当使用 A 时，都会使用专用版本.你也可以用它来专门化函数:
Now, whenever A<int> is used, the specialized version is used. You can also use it to specialize functions:
template<class T>
void foo(T t){
// general
}
template<>
void foo<int>(int i){
// for ints
}
// doesn't actually need the <int>
// as the specialization can be deduced from the parameter type
template<>
void foo(int i){
// also valid
}
通常情况下，你不应该专门化函数，因为简单的重载通常被认为是优越的:
Normally though, you shouldn't specialize functions, as simple overloads are generally considered superior:
void foo(int i){
// better
}
<小时>
现在，为了让它显得矫枉过正，以下是一个部分专业化:
template<class T1, class T2>
class B{
};
template<class T1>
class B<T1, int>{
};
与完全特化的工作方式相同，只是当第二个模板参数是 int(例如，B、B 等).
Works the same way as a full specialization, just that the specialized version is used whenever the second template parameter is an int (e.g., B<bool,int>, B<YourType,int>, etc).
相关文章