用折叠表达式填充数组时的语法问题 [英] Syntax issue when populating an array with a fold expression
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问题描述
是的,我可以使用 std :: initializer_list
。是的,甚至更容易,我可以进行聚合初始化。但这如何工作?我似乎无法将C ++ 17的fold表达式折叠起来。没有足够的例子。
Yes, I can use std::initializer_list
. Yes, even easier, I can do aggregate initialization. But how does this work? I can't seem to fold my head around C++17's fold expressions. There aren't enough examples out there.
这是我想出的内容:
template<class T, std::size_t N>
struct foo
{
T arr[N];
template<typename... Args>
constexpr foo(Args&&... pack)
{
static_assert(sizeof...(pack) <= N, "Too many args");
std::size_t i = 0;
(arr[i++] = ...);
}
};
int main()
{
foo<int, 5> a(1, 2, 3, 4, 5);
}
编辑:使用最新的Clang进行编译。支持折叠表达式。
Compiling with latest Clang. Fold expressions are supported.
实时示例: http:/ /coliru.stacked-crooked.com/a/777dc32da6c54892
推荐答案
您需要使用逗号运算符进行折叠,
You need to fold with the comma operator, which also solves the sequencing problem.
(void(arr[i++] = pack) , ...);
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