我想创建一个字符串字面量,用作模板参数。这会导致编译器陷入某种无限循环。问题在哪里,如何修复?
template <char...> struct slit { };
template <typename ...A>
constexpr auto make_slit(char const* const s, A const ...args)
{
return *s ? make_slit(s + 1, *s, args...) : slit<args...>();
}
int main()
{
auto const tmp_(make_slit("slit"));
return 0;
}
必须的错误(使用clang++ -std=c++1y
):
t.cpp:4:16: fatal error: recursive template instantiation exceeded maximum depth of 256
constexpr auto make_slit(char const* const s, A const ...args)
^
t.cpp:6:15: note: in instantiation of function template specialization 'make_slit<char, char, char, char, char, char, char, char, char, char, char, char, char, char, char,
char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char,
char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char,
char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char,
char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char,
char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char,
char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char,
char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char,
char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char,
char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char, char>' requested here
return *s ? make_slit(s + 1, *s, args...) : slit<args...>();
编辑: 请查看这个答案,它说明生成编译时切片类型是可行的。
slit<'a','b','c'>()
运行良好,我只需要一个生成函数。 - user1095108*s ?:
并不是一个编译时结构,据我所知。因为没有任何阻止你调用string s; cin >> s; make_slit(s.c_str());
。 - PeterT?:
的真值如何,它都会被实例化,因为它是表达式的一部分。 - PeterT