问题描述
对不起,标题是一个口。我正在处理类似于讨论的数组类。我想定义一个映射函数,它接受用户定义的函数并将其应用于数组的每个元素。为了进行类型检查,我想定义它,使用户指定的函数必须使用与传递给map函数相同数量的参数,以便
Sorry the title is a mouthful. I'm working on an array class similar to the one discussed here. I want to define a "map" function that takes a user-defined function and applies it to each element of the array. For the purposes of type-checking, I'd like to define it such that the user-specified function must take the same number of arguments as are passed to the map function, so that
double f(double a, double b) { return a + b; }
Array<double,2> x, y, z; x.map(f, y, z);
将编译,但
double g(double a, double b, double c) { return a + b + c; }
Array<double,2> x, y, z;. x.map(g, y, z);
不会,因为 g
我尝试过一种语法:
template<typename T, size_t ... Ns> class Array
{
template<class ... Args> inline const Array<T, Ns...>
map(T (*fn)(decltype(Args, double)...), Args...)
{
// doesn't compile
}
}
我认为这是接近的,但显然是错误的,因为它不编译。我非常感谢学习这样的操作的正确语法。
I think this is close, but obviously wrong, since it doesn't compile. I'd be grateful to learn the correct syntax for an operation like this.
推荐答案
template <typename T, std::size_t ... Ns>
struct Array
{
template <typename>
using arg_type = T;
template <class ... Args>
Array<T, Ns...> map(T (*fn)(arg_type<Args>...), Args...)
{
return {};
}
};
这篇关于如何使可变参数模板类方法接受函数指针作为参数,从函数模板派生类型?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!